Iron deficiency is the most widespread nutritional deficiency in the world, and one of the most insidious: it develops over months, hides behind fatigue that we attribute to work or lack of sleep, and can remain invisible on a simple blood count as long as anemia hasn't developed. Yet, long before this stage, iron deficiency already weighs on energy, concentration, hair, sleep and even the legs.
This guide takes stock, with evidence to back it up: what iron does and how the body regulates it, the three stages of deficiency, early and overlooked symptoms, what studies really say about fatigue and hair loss, who is at risk and why, how to read your ferritin levels correctly, how much iron you need, which foods provide it, which supplement to choose, and most importantly how to take it for real absorption. Without exaggerated promises, and without replacing your doctor.
14 mg of iron chelated to glycine (100% of NRV), combined with 80 mg of vitamin C for absorption and 200 µg of vitamin B9. The best tolerated form of iron, in one vegetable capsule per day. Made in France.
Iron deficiency progresses in three stages: depleted reserves (low ferritin), functional deficit, then iron deficiency anemia. You can therefore be deficient with normal hemoglobin and feel its effects: a French study reduced fatigue by nearly half by correcting ferritin below 50 µg/L in non-anemic women (Vaucher, CMAJ, 2012). The main causes are heavy periods, pregnancy, a diet low in heme iron, malabsorption, and in men or postmenopausal women, digestive bleeding that should be systematically investigated. To correct: confirm with a blood test, treat the cause, choose a well-tolerated form such as bisglycinate, and take it in the morning, every other day, away from tea, coffee and dairy products.
- Iron in the body: what it does, how it is regulated
- Iron deficiency or anemia: the 3 stages
- Symptoms of iron deficiency
- Iron deficiency and fatigue: proof without anemia
- Iron deficiency and hair loss
- Restless legs: the link with iron
- The causes: who is at risk?
- Diagnosis: reading your blood test (ferritin, TIBC, hemoglobin)
- How much iron per day?
- Iron-rich foods and absorption
- Supplementing with iron: which type, what dose, what frequency
- When oral supplementation is not enough
- Safety, overdose and interactions
- Choosing the right iron supplement
- Frequently asked questions
1. Iron in the body: what it does, how it is regulated
An adult contains 3 to 4 g of iron. Two-thirds are in thehemoglobin of red blood cells, which captures oxygen in the lungs and delivers it to tissues. Some is in the myoglobin of muscles, an oxygen reserve for physical effort. The rest is stored in the liver, spleen and bone marrow in the form of ferritin, or circulates bound to transferrin. A small fraction, which is essential, fuels hundreds of enzymes: those in the respiratory chain of mitochondria (cellular energy), DNA synthesis, dopamine and serotonin, thyroid and immunity. This explains why iron deficiency causes fatigue long before it causes anemia, and why it also affects mood, concentration and resistance to infections.
Iron has a unique feature: the body has no active way to eliminate it. It only loses one to two milligrams per day, through the shedding of intestinal and skin cells, plus menstrual losses in women. Everything depends on absorption, in the duodenum, and this absorption is controlled by a hormone produced by the liver,hepcidin. When reserves are full or there is inflammation, hepcidin rises and locks the door; when reserves drop, it falls and the intestine absorbs more. Two practical consequences, which we will return to later: inflammation can create a "functional" deficiency even though reserves are present, and each dose of iron ingested raises hepcidin for 24 to 48 hours, which changes the way a supplement should be taken (Pasricha, Lancet, 2021).
From a regulatory standpoint, EFSA recognizes six health claims for iron: it contributes to the normal formation of red blood cells and hemoglobin, normal oxygen transport, normal energy metabolism, reducing fatigue, normal cognitive function and normal immune system function. These formulations describe the maintenance of normal functions: an iron supplement does not "boost" someone who is not deficient.
2. Iron deficiency or anemia: the 3 stages
Common usage confuses "iron deficiency" and "anemia." These are two different things, and the distinction changes everything for diagnosis. A landmark review in the journal Blood notes that iron deficiency anemia affects more than 1.2 billion people, and iron deficiency without anemia is even more common (Camaschella, Blood, 2019). Here are the three stages:
| Stage | What happens | What blood tests show |
|---|---|---|
| 1. Depleted reserves | Ferritin stores decline, bone marrow still produces red blood cells normally. | Low ferritin (less than 30 µg/L), normal hemoglobin. Often already symptomatic (fatigue, hair loss, concentration problems). |
| 2. Functional deficit | Available iron is no longer sufficient for tissues or optimal hemoglobin production. | Low ferritin, transferrin saturation coefficient below 20%, hemoglobin still within normal range or at its lower limit. |
| 3. Iron deficiency anemia | Bone marrow lacks iron: it produces smaller red blood cells with less hemoglobin. | Hemoglobin below 12 g/dL (women), 13 g/dL (men), 11 g/dL (pregnancy); small red blood cells (MCV below 80 fL) and pale. |
The key point: a standard blood count only detects stage 3. A person complaining of fatigue whose "blood test is normal" has often had normal hemoglobin, without ferritin testing. It is ferritin testing, and if necessary transferrin saturation testing, that reveals the first two stages. We return to this in the diagnostic section.
3. Symptoms of iron deficiency
Because iron is involved both in oxygen transport and in hundreds of enzymes, symptoms are numerous and often attributed to something else. They develop gradually, which explains why many people only recognize them once the deficiency is advanced. Three categories:
Fatigue, shortness of breath, concentration
They appear from the stage of low reserves, without anemia.
Fatigue that does not improve with rest, decreased exercise tolerance, shortness of breath climbing stairs, palpitations, difficulties concentrating and with memory, irritability, low mood, sensitivity to cold and cold extremities, headaches, dizziness upon standing.
Pallor, skin, nails, hair, mouth
The mirror often speaks before the blood test.
Pallor of the face, inner eyelids and gums; dry skin; dull hair that falls more than usual; brittle, striated or spoon-shaped nails (koilonychia); smooth, red and painful tongue; cracks at the corners of the mouth; difficulty swallowing.
Restless legs, pica, infections
Rarely linked to iron, and yet characteristic.
Irrepressible need to move the legs in the evening (restless leg syndrome), irresistible cravings to crunch ice, eat dirt or clay (pica) or smell certain odors, recurrent ENT infections, in children growth delay and learning difficulties.
A clinical review sums up the situation well: beyond anemia, iron deficiency has multiple manifestations, including fatigue, hair loss and restless legs, and the most effective test to detect it is ferritin (DeLoughery, Med Clin North Am, 2017). If several of these signs coexist, especially in a menstruating woman, vegetarian or endurance athlete, a blood test is justified. If you have significant palpitations, shortness of breath at rest or fainting, consult without delay.
4. Iron deficiency and fatigue: evidence, even without anemia
This is the question everyone asks: "I'm tired, my hemoglobin is normal, can iron still help me?" A randomized trial conducted in France, among 44 general practitioners, answers this directly. 198 women aged 18 to 53 complaining of fatigue, with normal hemoglobin (above 12 g/dL) but ferritin below 50 µg/L, received for 12 weeks either iron (80 mg of elemental iron per day) or placebo.
The fatigue score decreased by 47.7% in the iron group versus 28.8% with placebo. Iron also increased hemoglobin and ferritin. The authors recommend considering supplementation in tired women whose ferritin is below 50 µg/L, and verifying its effect with a blood test after six weeks.
Vaucher P, Druais PL, Waldvogel S, Favrat B. CMAJ 2012;184(11):1247-1254. DOI: 10.1503/cmaj.110950
Two honest caveats. First, the placebo effect is real (nearly 30%), which reminds us that fatigue has many causes and that comprehensive testing (thyroid, vitamin D, B12, sleep) remains useful; our guide chronic fatigue: 11 validated plants and nutrients covers this. Second, the trial did not show improvement in quality of life, depression or anxiety: iron corrects iron-related fatigue, not everything else. But for the population most concerned, menstruating women with low ferritin, the benefit is clear and measurable within a few weeks. For athletes, the issue is the same with an added factor: endurance depends directly on oxygen transport (see fatigue or overtraining).
5. Iron deficiency and hair loss
The hair follicle is one of the fastest-dividing tissues in the body, and cell division consumes iron. When reserves drop, the body prioritizes vital functions and hair takes a back seat: the cycle shortens, more hairs enter the shedding phase, and hair density thins diffusely. This is telogen effluvium, the form of hair loss most frequently associated with iron deficiency in women.
Among 10,029 female participants, women suffering from non-scarring alopecia had ferritin levels 18.5 ng/mL lower than women without hair loss, and 21% of them had ferritin levels of 10 to 15 ng/mL or lower. The authors' conclusion: women who lose their hair may benefit from higher ferritin levels.
Treister-Goltzman Y, Yarza S, Peleg R. Skin Appendage Disord 2022;8(2):83-92. DOI: 10.1159/000519952
Dermatologists remain cautious about the exact threshold, and a reference review on micronutrients and hair loss notes that evidence of improvement with iron supplementation in deficient women exists but should be consolidated by large-scale trials (Almohanna, Dermatol Ther, 2019). In practice, when facing diffuse hair loss, the assessment almost always includes ferritin, and many practitioners target a value above 40 to 70 µg/L before concluding that iron is not a contributing factor. Hair loss also has other drivers (thyroid, zinc, vitamin D, hormones, stress), which we detail in hair loss: the 8 proven active ingredients.
6. Restless legs: the iron connection
This irresistible urge to move the legs in the evening or at night, accompanied by unpleasant sensations that ease with movement, affects 5 to 10% of adults and disrupts sleep. Its mechanism involves dopamine, whose synthesis depends on an iron-containing enzyme, and imaging studies show reduced iron in certain brain regions in affected individuals. Hence a distinctive feature: the ferritin thresholds used here are much higher than for classical iron deficiency.
After reviewing 31 studies, the expert panel concluded that oral iron (65 mg of elemental iron) is probably effective when ferritin is below or equal to 75 µg/L, and that intravenous iron (ferric carboxymaltose, 1,000 mg) is effective in moderate to severe forms when ferritin is below 300 µg/L, and may be proposed as first-line treatment in adults.
Allen RP, et al. Sleep Med 2018;41:27-44. DOI: 10.1016/j.sleep.2017.11.1126
If you experience restless legs in the evening, don't settle for "your ferritin is within normal range": ask for the exact value and discuss it with a doctor familiar with these thresholds. Restless legs are different from heavy legs, of venous origin, which we address in heavy legs: 11 validated remedies, and from nocturnal cramps, discussed in cramps: causes and solutions.
7. The causes: who is at risk of iron deficiency?
Women of childbearing age. This is by far the most affected population. Each cycle costs 15 to 30 mg of iron, more with heavy menstruation (more than 80 mL per cycle, meaning protection changes every two hours, blood clots, periods lasting more than 7 days). Epidemiological studies find low ferritin in one in five menstruating women in Europe. Endometriosis, fibroids, and copper IUDs increase losses (see endometriosis: symptoms and management).
Pregnancy and postpartum. Needs climb to 16 mg per day according to ANSES: blood volume increases by 40%, the fetus and placenta develop, and childbirth costs blood. Iron deficiency during pregnancy is associated with risk of prematurity and low birth weight, which is why ferritin is monitored and iron is often prescribed. In this situation, choice and dosage are the responsibility of the midwife or physician.
Children and adolescents. Growth multiplies needs, and adolescent girls face both growth and menstruation. In young children, a diet too high in dairy and low in meat or legumes is the classic cause.
Vegetarians and vegans. Their total iron intake is often adequate, but consists exclusively of non-heme iron, which is absorbed at 2 to 20% compared to 15 to 35% for iron from meat. Without a strategy (vitamin C at meals, legumes, avoiding tea), stores erode, especially in women. Iron adds to vigilance regarding vitamin B12.
Endurance athletes. Running, trail running, cycling, combat sports: hemolysis from impact, sweating, micro-digestive bleeding during exercise, and post-training inflammation (which raises hepcidin) deplete reserves. Low ferritin directly translates to a loss of aerobic performance, often confused with overtraining.
Absorption disorders. Celiac disease, sometimes revealed by isolated iron deficiency (recommendations suggest systematic screening), inflammatory bowel diseases, atrophic gastritis, infection with Helicobacter pylori, bariatric surgery (bypass, sleeve) and prolonged use of antacids (PPIs), which suppress the acidity necessary for iron absorption.
Digestive losses. Ulcer, polyps, angiodysplasias, colorectal cancer, hemorrhoidal disease, or simply regular use of aspirin or anti-inflammatory drugs. These are the causes to investigate as a priority in men and postmenopausal women. Repeated blood donations (one donation = 200 to 250 mg of iron) are a benign but real cause.
8. Diagnosis: reading your blood test
Four figures are usually sufficient, and a fifth one prevents errors:
| Marker | What it measures | Benchmarks |
|---|---|---|
| Ferritin | The body's iron reserves. The most sensitive and specific marker in the absence of inflammation. | Less than 15 µg/L: certain deficit (WHO). Less than 30 µg/L: very probable deficit. With fatigue or hair loss, many clinicians aim for above 50. Restless legs: less than 75 justifies treatment. |
| Transferrin saturation coefficient (TSC) | The portion of transferrin loaded with iron, that is, the iron actually available to tissues. | Less than 20%: functional deficit. Useful when ferritin is skewed by inflammation. |
| Hemoglobin | Oxygen transport capacity. Only decreases at stage 3. | Anemia if less than 12 g/dL (women), 13 g/dL (men), 11 g/dL (pregnancy). |
| MCV and MCHC | The size of red blood cells and their hemoglobin content. | MCV below 80 fL and low MCHC: microcytic hypochromic anemia, typical of iron deficiency (to distinguish from B12 or B9 deficiency, which produces oversized red blood cells). |
| CRP | Inflammation. Essential for interpreting ferritin. | If CRP is elevated, ferritin can be "normal" despite true deficiency: a threshold of 100 µg/L and the TSC are then used. |
The most common pitfall is that of falsely reassuring ferritin. Ferritin is also an inflammation protein: infection, chronic disease, obesity, intense training, or even a simple cold can raise it. A review in the Lancet emphasizes this point: in an inflammatory context, hepcidin sequesters iron and ferritin rises, while tissues lack it (Pasricha, Lancet, 2021). This is why recommendations for heart failure, kidney disease, or IBD define deficiency as ferritin below 100 µg/L, or between 100 and 300 with TSC below 20% (Cappellini, Am J Hematol, 2017). Request a CRP at the same time as ferritin; it's the only way to read the result correctly. To decode your figure step by step, read low ferritin: symptoms, thresholds, and what to do.
Another useful reference point: "serum iron" alone is useless. It varies from hour to hour, with meals and supplement intake. If your prescription only includes this, ask for ferritin. Our guide to the most common deficiencies details other useful tests when fatigue persists.
9. How much iron per day? Needs according to your profile
| Population | Reference (mg per day) | Note |
|---|---|---|
| Adult men | 11 | Physiological losses only (approximately 1 mg per day) |
| Women with light menstrual losses or menopausal | 11 | Same level as men |
| Women with heavy periods | 16 | Affects approximately one in five women |
| Pregnant women | 16 | Frequent supplementation, on prescription |
| Children 1 to 6 years old | 5 to 7 | Period at risk: growth and milk-based diet |
| Adolescent girls 13 to 17 years old | 13 | Growth + menstruation |
| NRV for labeling (adults) | 14 | EU Regulation No. 1169/2011, labeling values |
ANSES 2021 and EFSA 2015 nutritional references; indicative values for a healthy population, excluding correction for confirmed deficiency.
Two concepts make all the difference. Heme iron, found in meat, fish and offal, is absorbed at 15 to 35% and is little affected by other foods in the meal. Non-heme iron, from plants, eggs, dairy products and all supplements, is absorbed at 2 to 20% and depends heavily on what accompanies it: vitamin C and animal proteins increase it, tannins from tea and coffee, calcium and phytates from whole grains reduce it. This explains why a plant-based diet "rich in iron" on paper may still leave reserves low.
10. Iron-rich foods and how to absorb it better
| Food | Iron (mg per 100 g) | Type and reference |
|---|---|---|
| Black pudding | 20 to 23 | Heme iron. The richest food: one serving easily covers the daily requirement |
| Liver (veal, poultry, lamb) | 7 to 13 | Heme iron. Also rich in B12 and vitamin A (limit during pregnancy) |
| Clams, mussels, oysters | 5 to 15 | Heme iron. Clams are among the richest sources |
| Red meat (beef, lamb) | 2 to 3.5 | Heme iron. A 150 g steak provides 3 to 5 mg well absorbed |
| Sardines, mackerel, tuna | 1 to 3 | Heme iron. Bonus omega-3 |
| Cooked lentils | 3 to 3.5 | Non-heme iron. 200 g cooked = 6 to 7 mg, should be paired with vitamin C |
| Tofu, tempeh | 2.5 to 5 | Non-heme iron. Good source for vegetarians |
| Pumpkin seeds, sesame | 8 to 15 | Non-heme iron. Rich but consumed in small quantities |
| Cocoa powder, 70% dark chocolate | 10 to 12 / 6 to 11 | Non-heme iron. Polyphenols limit absorption |
| Cooked spinach | 2 to 3.5 | Non-heme iron. Poorly absorbed (oxalates): the Popeye legend |
| Spirulina, moringa (powders) | 25 to 30 | Non-heme iron. High content, but one 5 g tablespoon provides 1 to 1.5 mg: a supplement, not a solution |
Indicative values from the Ciqual table (ANSES) and USDA, before absorption. The ranges reflect variations depending on origin and cooking method.
A few simple rules multiply plant-based iron absorption: add a source of vitamin C to the meal (citrus fruits, kiwi, bell pepper, parsley, or an organicacerola powder), which can double or even triple the absorption of non-heme iron; keep tea and coffee at least one hour away, and preferably two, from meals rich in iron; separate calcium (dairy products, supplements) from iron intake; soak or sprout legumes and grains to reduce their phytates; and cook in cast iron, which releases some iron into acidic dishes. The spirulina and moringa usefully complement a plant-based plate, without replacing targeted supplementation when reserves are already low. For an overview, see the collection vitamins and minerals.
The Bisglycinate Iron Nutrition•pro provides 14 mg of iron chelated with glycine (100% of the NRV), with 80 mg of vitamin C for absorption and 200 µg of vitamin B9. One vegetable capsule per day, with no metallic taste, manufactured in France.
Discover Bisglycinate Iron →Not recommended in case of hemochromatosis, during pregnancy and breastfeeding without medical advice. A confirmed deficiency should be corrected with your doctor.
11. Supplementing: which iron, what dose, what schedule
What form of iron?
All forms provide iron, but they are not equal on two decisive points: tolerance and bioavailability. The ferrous sulfate is the historical reference for treatments, effective and inexpensive, but feared for its digestive effects. A meta-analysis of 43 trials quantified it:
Ferrous sulfate multiplies by 2.3 the risk of adverse digestive effects (nausea, pain, constipation, diarrhea) compared to placebo, and by 3 compared to intravenous iron, with no clear relationship to dose. These effects are the leading cause of treatment discontinuation.
Tolkien Z, et al. PLoS One 2015;10(2):e0117383. DOI: 10.1371/journal.pone.0117383
The bisglycinate iron is a chelated form: the iron atom is bound to two glycine molecules, which protects it from meal inhibitors (phytates, tannins) and allows it to cross the intestinal wall via a different pathway than ferrous salts, with less free irritating iron in the digestive tract. The trials confirm this:
Compared to other iron supplements, ferrous bisglycinate taken for 4 to 20 weeks increased hemoglobin more in pregnant women and caused nearly three times fewer adverse digestive effects (ratio 0.36). The authors call for more trials in other populations.
Fischer JAJ, Cherian AM, Bone JN, Karakochuk CD. Nutr Rev 2023;81(8):904-920. DOI: 10.1093/nutrit/nuac106
In fairness, one limitation: in a trial of 480 Cambodian women, most of whom were not deficient, 18 mg of bisglycinate did not raise ferritin as much as 60 mg of sulfate (84 versus 99 µg/L after 12 weeks), with no difference in intestinal inflammation (Fischer, J Nutr, 2023). In other words, better absorption per milligram does not compensate for a dose three times lower when the goal is to quickly replenish very low reserves. Bisglycinate at nutritional dose is the ideal form for moderate deficiency, maintenance, or a person who does not tolerate ferrous salts; established anemia requires a corrective dose prescribed by a physician, regardless of form.
| Form | Absorption | Tolerance | Strengths | Use |
|---|---|---|---|---|
| Ferrous sulfate | 10 to 15%, highly sensitive to meals | Low: digestive risk x 2.3 (Tolkien 2015) | Most studied, least expensive, high doses available | Medical treatment of anemia |
| Fumarate, ferrous gluconate | Similar to sulfate | Similar, sometimes slightly better | Classical alternatives | Medical treatment |
| Iron bisglycinate | 2 to 4 times higher per mg, little sensitive to inhibitors | Good: 3 times fewer digestive effects (Fischer 2023) | Moderate dose sufficient, no metallic taste, no constipation | Moderate deficiency, maintenance, digestive sensitivity, plant-based diet |
| Liposomal iron, sucrosomial | Good, more recent data | Good | Interesting in case of intolerance | Alternative, more costly |
| Intravenous iron | 100% (infusion) | Good with modern formulations, rare reactions | Restores reserves in 1 to 2 infusions | Hospital, by prescription |
What dose?
It all depends on the stage. Maintenance or prevention (menstruating woman, vegetarian, athlete, ferritin between 30 and 50 without anemia): 14 to 30 mg of elemental iron per day is sufficient, ideally as bisglycinate with vitamin C; this is the positioning of Iron bisglycinate Nutrition•pro (14 mg per capsule). Moderate deficiency (ferritin below 30, normal hemoglobin): 30 to 60 mg per day or every other day, in agreement with your physician, for a minimum of 3 months. Anemia : 80 to 200 mg per day in prescribed treatment, with monitoring. Beyond 60 to 80 mg per dose, absorption does not increase further; only digestive effects increase.
What rhythm? The discovery that changes everything
For decades, iron was recommended to be divided into two or three daily doses. Two Swiss trials overturned this practice by measuring actual absorption with iron marked by isotopes:
In women with low iron stores, 60 mg of iron taken every other day was absorbed at 21.8% compared to 16.3% with daily dosing—a third more—because each dose raises hepcidin which blocks the next dose. Dividing a 120 mg dose into two doses provided no benefit and increased hepcidin. Conclusion: a single dose in the morning, every other day, optimizes absorption.
Stoffel NU, et al. Lancet Haematol 2017;4(11):e524-e533. DOI: 10.1016/S2352-3026(17)30182-5
This regimen has since been confirmed in anemic women and adopted in reference reviews (Pasricha, Lancet, 2021). It has a second advantage: fewer doses means fewer digestive effects and better compliance. For moderate nutritional intake that is well-tolerated like bisglycinate, daily dosing remains possible; for corrective doses, every other day has become the standard.
And black stools? They are normal with iron and harmless. Constipation may occur with ferrous salts: hydration, fiber (psyllium husk) or switching to bisglycinate usually resolves it. The complete timing instructions (morning or evening, with what, away from what, mistakes to avoid) are in when to take iron. To compare forms in detail, our article iron bisglycinate vs other iron forms goes further.
12. When oral route is not enough: intravenous iron
Oral iron remains the first-line treatment in the vast majority of cases (Camaschella, NEJM, 2015). But certain situations make it fail: uncontrolled celiac disease, active IBD, gastric bypass, bleeding that exceeds what the intestine can absorb, chronic inflammation that locks absorption via hepcidin, or simply intolerance so severe the treatment is abandoned. Hematologists point out that old fears about allergic reactions concerned discontinued formulations; current forms (carboxymaltose, desiromaltose) allow a complete dose in one infusion lasting minutes to an hour, with faster and more sustained hematological response, including during pregnancy from the second trimester onward (Auerbach, Am J Hematol, 2016). This decision belongs to the doctor, who weighs benefits, risks, and cost in each situation.
13. Safety, overdose, and interactions
Unlike water-soluble vitamins, excess iron is not eliminated : it accumulates in the liver, heart, and pancreas, where it promotes oxidative stress. This is why supplementing "for energy" without confirmed deficiency is a bad idea, and why blood work always precedes supplementation. The EFSA has not set an upper safety limit due to insufficient data, but digestive effects become common beyond 45 to 60 mg per dose.
Hemochromatosis and iron overload : iron is contraindicated. Genetic hemochromatosis affects approximately one person in 300 in France and often goes unnoticed: elevated ferritin and TSAT before any supplementation should raise concern.
Children : accidental ingestion of iron tablets is one of the leading causes of serious poisoning in young children. Keep bottle closed, out of reach, always.
Medications : iron decreases the absorption of levothyroxine, certain antibiotics (tetracyclines, quinolones), bisphosphonates, and levodopa; space them at least 2 hours apart, 4 hours for levothyroxine. Conversely, antacids (PPIs), calcium, and certain gastric coatings reduce iron absorption.
Pregnancy, breastfeeding, children, chronic illness : needs and doses differ; consult a healthcare professional before any supplementation. Do not exceed the stated daily dose and do not substitute supplements for a varied and balanced diet.
Infections : during acute infection, the body deliberately locks iron; supplementation is discussed once the episode has passed.
14. Choosing your iron supplement wisely
- The elemental iron dose, clearly legible. "70 mg of iron bisglycinate" means 14 mg of iron; "100 mg of ferrous sulfate" means approximately 20 mg. Always compare elemental iron.
- The named form : bisglycinate (or chelated bisglycinate), rather than vague "iron" or "marine iron."
- Combination with vitamin C (60 to 100 mg) within the same dose, which increases non-heme iron absorption.
- Vitamin B9 (folates), useful for women of childbearing age and in any anemia, as iron and folates work together in red blood cell production (see our guide tofolic acid).
- A clean capsule : vegetable capsule (HPMC), without titanium dioxide, without colorants or flavors, traceable manufacturing.
- A dose adapted to your situation : 14 to 30 mg for maintenance and moderate deficiencies, prescription required beyond.
14 mg of iron chelated to glycine, 80 mg of vitamin C and 200 µg of vitamin B9 in a vegetable capsule. Without metallic taste or digestive discomfort, for optimal daily iron intake. Made in France.
Discover Iron bisglycinate →Choose the situation that best matches yours: the answer appears right below.
You are in the most affected population. Request ferritin, hemoglobin, and CRP testing. If ferritin is below 50 with fatigue, a well-tolerated iron supplement is justified: Bisglycinate Iron in the morning, away from tea and coffee, for 3 months, then retest. If your periods last more than 7 days or require you to change protection every two hours, also consult a gynecologist: treating the cause prevents relapse.
Vitamin C with each meal rich in plant-based iron, tea and coffee taken separately, soaked legumes, and ferritin tested once a year. If it's low, Bisglycinate Iron is the supplement best suited for regular nutritional intake. For endurance, also monitor vitamin D and, if you are vegetarian, vitamin B12.
Digestive effects come mainly from ferrous salts and split doses. Switch to a chelated form like Bisglycinate Iron, in a single dose in the morning, every other day if the dose is high, with vitamin C. If ferritin doesn't rise in 8 weeks or if malabsorption is suspected, discuss intravenous iron with your doctor.
For you, iron deficiency is a signal, not an inevitability. Guidelines recommend digestive exploration (screening for bleeding) and celiac disease screening before any treatment. Schedule an appointment with your doctor with your results; iron will come after diagnosis, and it will then be prescribed at the appropriate dose.
This test provides guidance; it does not replace blood work or professional medical advice.
Frequently asked questions about iron deficiency
What are the first symptoms of iron deficiency?
Fatigue that doesn't improve with rest, decreased endurance, shortness of breath with exertion, difficulty concentrating, unusual sensitivity to cold, and paleness (face, inside eyelids, gums). These signs often appear before anemia, as soon as reserves (ferritin) are low.
Can you have iron deficiency without anemia?
Yes, this is actually the most common case. Iron deficiency progresses in three stages: depleted reserves (low ferritin, normal hemoglobin), functional deficit, then iron-deficiency anemia. A French trial showed that correcting ferritin below 50 µg/L reduced fatigue by nearly half in women with normal hemoglobin (Vaucher, CMAJ, 2012).
What ferritin level indicates iron deficiency?
Ferritin below 15 µg/L indicates definite deficiency (WHO) and most clinicians use a threshold of 30 µg/L. In case of inflammation (elevated CRP), ferritin rises artificially: a threshold of 100 µg/L and a transferrin saturation coefficient below 20% are then used. The interpretation is up to the physician.
Does iron deficiency cause hair loss?
A meta-analysis of 36 studies (10,029 women) shows that women suffering from diffuse hair loss have ferritin levels averaging 18.5 ng/mL lower than others, and that one in five women has ferritin of 15 ng/mL or less (Treister-Goltzman, 2022). Iron does not explain all hair loss, but low ferritin deserves to be corrected.
What is the link between iron deficiency and restless legs?
Restless legs syndrome is associated with iron deficiency in the brain. International recommendations (IRLSSG, 2018) propose oral iron treatment when ferritin is less than or equal to 75 µg/L, and intravenous iron in moderate to severe forms with ferritin below 300 µg/L, on medical advice.
What are the causes of iron deficiency?
Increased needs (heavy periods, pregnancy, growth, endurance sports), insufficient intake (vegetarian or low-meat diet), reduced absorption (celiac disease, long-term antacids, bariatric surgery, gastritis) or chronic blood loss, particularly digestive. In a man or postmenopausal woman, a deficiency always requires investigating bleeding.
How much iron per day?
According to ANSES, 11 mg per day for an adult man and a woman with low menstrual losses, 16 mg for a woman with heavy periods and during pregnancy. Only 10 to 15% of dietary iron is absorbed on average, more for heme iron (meat, fish) than for plant iron.
Which foods are richest in iron?
Black pudding, liver, shellfish, red meat and fish for heme iron, which is well absorbed. On the plant side, lentils, tofu, pumpkin seeds, cocoa and fortified cereals, whose iron is absorbed less well but much better with vitamin C (citrus, bell pepper, kiwi) at the same meal.
Which iron supplement to take: sulfate or bisglycinate?
Ferrous sulfate is the standard treatment, but it doubles the risk of digestive disorders compared to placebo (Tolkien, PLoS One, 2015). Iron bisglycinate, chelated with glycine, causes nearly three times fewer digestive effects and increases hemoglobin more in pregnant women (Fischer, Nutr Rev, 2023). At low dose, it raises ferritin less than a high dose of sulfate: the dose matters as much as the form.
Should iron be taken daily or every other day?
Two randomized trials showed that taking every other day, once in the morning, increases absorption by about one-third compared to daily intake, because each dose raises hepcidin, the hormone that blocks iron absorption for 24 to 48 hours (Stoffel, Lancet Haematol, 2017). Divided doses throughout the day provide no additional benefit.
When to take iron, morning or evening, with or without meals?
In the morning, on an empty stomach or one hour before a meal, with water or juice rich in vitamin C. Keep it away (at least 2 hours) from tea, coffee, dairy products, calcium and antacids, which significantly reduce absorption. If the stomach doesn't tolerate taking it on an empty stomach, a light meal is better than stopping altogether.
How long does it take for iron deficiency to be corrected?
Fatigue often improves in 4 to 6 weeks, hemoglobin rises in 4 to 8 weeks, but rebuilding reserves (ferritin) takes 3 to 6 months. A blood test at 6 weeks and then at 3 months allows you to verify that treatment is working and that the cause has been addressed.
Can iron supplements be dangerous?
At nutritional doses, iron is safe in someone who is deficient. It is not recommended in cases of hemochromatosis or any iron overload, and supplements should be kept out of children's reach, as massive ingestion is toxic in children. Supplementing without proven deficiency provides no benefit and may mask a serious cause.
When are iron tablets not enough?
In case of major digestive intolerance, malabsorption (celiac disease, Crohn's, bariatric surgery), significant bleeding or need for rapid correction, the doctor may prescribe intravenous iron, whose modern formulations rebuild reserves in one or two infusions (Auerbach, Am J Hematol, 2016).
Can pregnant women take iron bisglycinate?
Pregnancy multiplies needs and iron is often prescribed for it, but the dose and form are the responsibility of the doctor or midwife, who base their decision on blood tests. Do not start iron supplementation while pregnant without medical advice.
Do tea and coffee really prevent iron absorption?
Yes. Tannins in tea and polyphenols in coffee can reduce non-heme iron absorption by 50 to 90% if consumed at the same time. Calcium (dairy products, supplements) and phytates from whole grains also have an inhibitory effect. Space them 1 to 2 hours apart from iron-rich meals or from taking supplements.
- Ferritin
- Iron storage protein. Its blood level reflects the body's reserves, except in case of inflammation where it rises artificially.
- Hepcidin
- Hormone produced by the liver that controls iron absorption. It rises when reserves are full, in cases of inflammation, and for 24 to 48 hours after each iron dose.
- Transferrin saturation coefficient (TSC)
- Proportion of transferrin, a transport protein, loaded with iron. Below 20%, it indicates functional deficiency, even when ferritin appears normal.
- Heme and non-heme iron
- Heme iron (meat, fish, offal) is absorbed at 15-35%; non-heme iron (plant foods, eggs, dairy, supplements) at 2-20%, depending on the rest of the meal.
- Iron deficiency anemia
- Anemia due to lack of iron: lowered hemoglobin and small (microcytic) and pale (hypochromic) red blood cells. Final stage of deficiency.
- MCV
- Mean corpuscular volume, the size of red blood cells. Below 80 fL in iron deficiency, above 100 fL in B12 or B9 deficiency.
- Hemochromatosis
- Genetic disease of iron overload, common in France (approximately 1 person in 300), which contraindicates any supplementation.
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