It's three in the morning, the calf suddenly tightens, hard as a stone, and the pain wakes you up. A cramp lasts an average of nine minutes, affects more than one in three adults, more so with age, and often returns the following night.
This guide first provides the technique to stop it in the moment. Then what we know about its causes, including medications you wouldn't suspect, and what trials show to prevent it: stretching, vitamin K2, magnesium, B vitamins and quinine, with their actual level of evidence. And the signs that indicate a calf pain is not a cramp.
In the moment : stretch the calf, toes pulled toward you, or get up and place your heel on the ground; the cramp usually subsides within a few tens of seconds. The causes : most often no disease, fatigue and hyperexcitability of the nerve and muscle, more frequent with age; but certain medications notably favor them, long-acting bronchodilators and diuretics at the forefront, and venous, arterial, kidney or liver diseases are associated with them.
To prevent : stretches of the calf and back of the thigh each evening before bed, which reduce frequency and intensity in one trial; the vitamin K2, which reduced cramps from 2.6 to 1 per week, versus 3.6 with placebo, in a trial in those over 65; magnesium, with no net effect in elderly people without deficiency according to Cochrane, with mixed results during pregnancy; quinine, effective but abandoned due to its rare and serious adverse effects. Consult if the calf remains swollen and painful, if pain occurs when walking, or if cramps are accompanied by weakness.
In the moment: the move that stops the cramp
A cramp is an involuntary, sudden and painful contraction of a muscle, which does not relax on its own. The move that stops it consists of stretching this muscle, that is, doing exactly the opposite of what it is currently doing. For the calf, this means bringing the tip of your foot toward you.
Why the calf, and why at night
Two hundred eighteen people drawn from a general practice register answered the questionnaire, and fifteen others were contacted by telephone. The prevalence of rest cramps was 37%, higher in older people. They most often affected the leg muscles, in 83% of the 86 people affected, and occurred especially at night, in 73% of cases. An episode lasted an average of 9 minutes. Most had infrequent cramps, but 40% had more than three per week and 6% at least one per day or night. Twenty-one percent found them very bothersome, and only 32% had discussed them with their doctor. Rest cramps were associated with symptoms of angina pectoris and intermittent claudication.
Naylor JR, Young JB. Age Ageing 1994;23(5):418-420. DOI: 10.1093/ageing/23.5.418
The exact mechanism remains poorly understood. The review fromAmerican Family Physician concludes that nocturnal cramps probably come from a muscle fatigue and a dysfunction of the motor nerve, rather than an electrolyte imbalance. Up to 60% of adults say they have experienced it. The calf is the most affected muscle and nighttime is the most frequent occurrence: when lying down with the foot extended under tightly tucked sheets, the calf remains shortened for hours, a position that favors contraction.
The same journal lists associated situations: vascular diseases, lumbar canal stenosis, cirrhosis, hemodialysis, pregnancy. And a series of medications, the subject of the next section.
Causes to check: medications and diseases
Health databases of 4.2 million British Columbia residents were analyzed to determine, in adults aged 50 and older, whether new prescriptions of quinine, a marker of the start of cramp treatment, increased in the year following the introduction of a diuretic, a statin, or a long-acting beta-2 bronchodilator. Adjusted ratios were 1.47 for diuretics, 1.16 for statins, and 2.42 for long-acting bronchodilators. Among diuretics, they reached 2.12 for potassium-sparing agents and 1.48 for thiazides, compared to 1.20, not significant, for loop diuretics. Overall, 60.3% of people treated for cramps had received at least one long-acting bronchodilator, a potassium-sparing diuretic, or a thiazide over thirteen years. Doctors should keep in mind that these treatments can worsen nighttime cramps.
Garrison SR, Dormuth CR, Morrow RL, Carney GA, Khan KM. Arch Intern Med 2012;172(2):120-126. DOI: 10.1001/archinternmed.2011.1029
| Medication or condition | Link with cramps | Source |
|---|---|---|
| Long-acting beta-2 bronchodilators | Cramp treatments multiplied by 2.4 within one year | Cohort of 4.2 million residents |
| Potassium-sparing diuretics | Multiplied by 2.1 | Cohort of 4.2 million residents |
| Thiazide diuretics | Multiplied by 1.5 | Cohort of 4.2 million residents |
| Statins | Weak link, 1.16 | Cohort of 4.2 million residents |
| Intravenous iron, conjugated estrogens, raloxifene, naproxen, teriparatide | Strongly associated | American Family Physician journal |
| Vascular diseases, lumbar stenosis, cirrhosis, dialysis, pregnancy | Associated | American Family Physician journal |
These associations do not mean you should stop a treatment: a bronchodilator or diuretic has a far more important reason for being than a cramp. They mean you should discuss it with your doctor if cramps appeared or worsened after starting or changing the dose of a medication; an alternative sometimes exists.
Effort cramps
Two hundred ten triathletes competing in an Ironman were followed, with questionnaire, blood tests, and weigh-ins before and after the race. Forty-three experienced cramps. There was no difference between the two groups for blood electrolyte concentrations or for weight change. Cramps were associated with faster planned and actual race times, with comparable training. A faster race pace and a history of cramps in the previous ten races were the only two independent risk factors. Dehydration and electrolyte imbalances are not the cause of these cramps; running fast, thus at high intensity, is more likely the cause.
Schwellnus MP, Drew N, Collins M. Br J Sports Med 2011;45(8):650-656. DOI: 10.1136/bjsm.2010.078535
Effort cramp is therefore mainly a cramp of neuromuscular fatigue : it occurs when the muscle works harder or longer than it is trained for. What prevents it: a pace suited to your preparation, specific training for the intended duration and intensity, and stretching the affected muscle as soon as it occurs. Drinking remains necessary for performance and safety during prolonged efforts, but water and salts alone are not enough to prevent it. Our article on electrolytes details this point.
Preventing night cramps: what the trials show
Eighty adults over 55 years old prone to nocturnal cramps, not treated with quinine, were randomly assigned. The experimental group stretched their calves and the muscles at the back of the thigh each evening, just before bed, for six weeks; the control group did not perform specific stretches. All participants completed the study. At six weeks, the frequency of nocturnal cramps had decreased significantly more in the stretching group, with a mean difference of 1.2 cramps per night, and their intensity also decreased, by 1.3 cm on a 10 cm visual scale. Daily stretching before bedtime reduces the frequency and intensity of nocturnal cramps in older adults.
Hallegraeff JM, van der Schans CP, de Ruiter R, de Greef MH. J Physiother 2012;58(1):17-22. DOI: 10.1016/S1836-9553(12)70068-1
An older British trial in 191 patients on long-term quinine had found no effect of calf stretching alone, recommended but not supervised. The difference likely lies in the protocol: the Dutch trial also stretched the back of the thigh, each evening just before bed, in people not taking quinine. Without risk and free of charge, stretching deserves six weeks of regular trial.
One hundred ninety-nine people aged 65 and older, living at home and having had at least two nocturnal cramps during two weeks of screening, received 180 µg of vitamin K2 daily, in the form of menaquinone 7, or an identical placebo for eight weeks. The baseline weekly frequency was comparable: 2.60 cramps in the vitamin K2 group and 2.71 in the placebo group. During the intervention, it fell to 0.96 per week under vitamin K2 and was 3.63 under placebo, a difference of 2.67 cramps per week. The intensity and duration of cramps also decreased more with vitamin K2. No adverse effects related to vitamin K2 were identified.
Tan J, Zhu R, Li Y, et al. JAMA Intern Med 2024;184(12):1443-1447. DOI: 10.1001/jamainternmed.2024.5726
It is a trial conducted in China in older people that needs to be replicated; but it is the first treatment to show a clear effect without adverse effects in a rigorous trial. One absolute precaution: vitamin K opposes the action of anticoagulants that are antivitamin K antagonists, such as warfarin or fluindione. Anyone taking anticoagulants should speak to their doctor before taking it.
Eleven trials and 735 people were included: five in pregnant women, five in people with idiopathic cramps, mostly elderly, one in cirrhosis. For idiopathic cramps in older people, the most common form, the frequency differences between magnesium and placebo were small and not statistically significant, with moderate to high certainty of evidence; the same applied to intensity and duration. During pregnancy, trial results were contradictory. It is unlikely that magnesium provides clinically significant prevention of cramps in older adults; for pregnancy-related cramps, the literature is contradictory and further research is needed. No trial evaluated magnesium for effort-induced cramps.
Garrison SR, Korownyk CS, Kolber MR, et al. Cochrane Database Syst Rev 2020;9:CD009402. DOI: 10.1002/14651858.CD009402.pub3
This result concerns idiopathiccramps, with no identified cause, in older people whose magnesium was not measured as low. It says nothing about people with insufficient intake, nor about those in whom a blood test shows a deficiency, a situation where magnesium is corrected. Magnesium plays a role in muscle contraction and relaxation; our article on magnesium provides a full overview of what it does and does not do.
<<<29>>> B vitamins vitamines B have one small positive trial: in 28 older hypertensive people, a complex of vitamins B1, B2, B6 and B12, three times daily for three months, eliminated cramps in 86% of participants, with no change under placebo. The trial is old, small, at high doses, and has not been replicated; a small study points in the same direction during pregnancy.
<<<32>>> Quinine quinine, long prescribed, is effective: in 23 trials and 1,586 participants, it reduced the number of cramps by 28% over two weeks. But it carries the risk of rare and sometimes serious adverse effects, including blood disorders, and it is no longer recommended for cramps; several countries have severely restricted its prescription.
| Avenue | What the trials show | Level of evidence |
|---|---|---|
| Stretching before bedtime | Frequency and intensity decreased at six weeks, calves and back of thighs | One positive trial, one negative on calf alone; without risk |
| Vitamin K2, 180 µg per day | 2.7 fewer cramps per week versus placebo after age 65 | A rigorous trial, to be reproduced |
| Magnesium | No net effect in older adults without deficiency; mixed results during pregnancy | Cochrane, moderate certainty |
| B Vitamins | Remission in 86% in a small trial | Weak, not reproduced |
| Quinine | Number of cramps decreased by 28% | Effective, but rare serious adverse effects: discontinued |
Pregnancy, foot, fingers: other types of cramps
Eight small trials and 576 pregnant women were included. Results could not be pooled, as the outcome measures were assessed differently from one trial to another. For oral magnesium, results on cramp frequency were contradictory: one trial found more women without cramps after treatment, others found little or no difference. Calcium had an uncertain effect, one small trial suggested a benefit of B vitamins, and vitamin D, alone or with calcium, made little difference. The certainty of evidence was low to very low. Available data do not allow us to say whether any of these treatments is effective against pregnancy-related cramps.
Luo L, Zhou K, Zhang J, Xu L, Yin W. Cochrane Database Syst Rev 2020;12:CD010655. DOI: 10.1002/14651858.CD010655.pub3
During pregnancy, especially in the third trimester, calf cramps are common. Stretching before bedtime remains the first measure. Magnesium is often recommended, with mixed results; any supplement should be discussed with your midwife or doctor.
The foot and toes : same mechanism, same measure. Pull your toes upward by hand, or place your foot flat on the ground and press down. Appropriate footwear and stretching of the arch and calf in the evening often help. A foot cramp that repeatedly occurs after the same activity, or that is accompanied by tingling, should be shown to a doctor.
The fingers and hand : a single hand cramp after a gripping effort is treated by opening the hand and gently stretching the fingers backward. By contrast, involuntary finger clenching that always occurs during the same task, such as writing or playing an instrument, often indicates something else—a functional dystonia—and should be evaluated by a neurologist.
When it's not a cramp
The calf remains painful, swollen, warm, or red after the episode, especially after a long trip, immobilization, surgery, or while taking hormonal contraception: deep vein thrombosis must be ruled out, which is an emergency. Pain appears with walking and subsides when you stop : this is a possible sign of peripheral artery disease, claudication, associated with rest cramps in population surveys.
Cramps are accompanied by weakness, muscle wasting, small visible muscle twitches under the skin, sensory disturbances, or involve many muscles: neurological evaluation is necessary. Cramps appeared with a new medication, or are accompanied by excessive thirst, abundant urination, severe fatigue: the doctor will check medications, blood glucose, kidney function, thyroid, and electrolytes.
Restless legs syndrome is not a cramp either: it is an irresistible urge to move the legs, with unpleasant sensations, relieved by movement, without muscle hardness. The review in theAmerican Family Physician notes that questioning and examination are generally sufficient to make the distinction, without additional tests.
The plan, in order
Microencapsulated magnesium Magshape® and magnesium malate, with taurine and vitamin B6, in four capsules per day spread throughout the day. For insufficient magnesium intake and increased needs, in addition to evening stretches. During pregnancy or with ongoing treatment, consult your doctor or midwife.
See Magnesium+Our general guide to cramps covers all locations.
Frequently asked questions
How do you relieve a calf cramp?
By stretching the calf: leg extended, bring the tip of your foot toward you, by hand or with a towel, or get up and press your heel to the ground while walking a few steps. The contraction usually subsides within a few dozen seconds. Then massage and warm the muscle; residual pain may last a few hours. Avoid: pointing your foot, which prolongs the cramp.
Why do you get calf cramps at night?
Most often without any underlying disease. Nocturnal cramps probably come from muscle fatigue and motor nerve dysfunction, rather than a lack of electrolytes. When lying down with the foot extended, the calf remains shortened for hours, a position that favors contraction. They affect 37% of adults in a population survey, more with age, and 73% of episodes occur at night.
A calf cramp means a lack of what?
Not necessarily a lack of something. In older adults, magnesium trials showed no clear effect on cramps without deficiency according to the 2020 Cochrane review, and in athletes, a study of 210 triathletes found no link with dehydration or sodium. A deficiency in magnesium, potassium, or calcium can cause cramps, but it is confirmed by a blood test. Most often, the cause is neuromuscular fatigue, medication, or an associated condition.
Which medications cause cramps?
In a study of 4.2 million residents of British Columbia, cramp treatments doubled 2.4 times in the year following introduction of a long-acting beta-2 bronchodilator, increased 2.1 times after a potassium-sparing diuretic, 1.5 times after a thiazide diuretic, with a weak link for statins. The review in theAmerican Family Physician adds intravenous iron, conjugated estrogens, raloxifene, naproxen, and teriparatide. Don't stop anything on your own: talk to your doctor.
Is magnesium effective against cramps?
In elderly people with cramps of no identified cause and without deficiency, the 2020 Cochrane review of eleven trials and 735 participants shows no net effect. During pregnancy, results are contradictory. Magnesium retains its value when intake is insufficient or when a deficiency is documented, since it plays a role in muscle contraction and relaxation. Side effects are mainly digestive, causing diarrhea.
Does vitamin K2 really work against cramps?
A randomized trial published in 2024 in JAMA Internal Medicine strongly suggests it does: in 199 people aged 65 and over, 180 µg of vitamin K2 per day for eight weeks reduced nighttime cramps from 2.6 to 1 per week, compared to 3.6 under placebo, with a decrease in intensity and duration and no side effects. It is a single trial, to be reproduced. Vitamin K opposes vitamin K antagonist anticoagulants: never without medical advice if you are taking them.
Do stretches prevent nighttime cramps?
In a randomized trial of 80 adults over 55 years old, stretching the calves and back of the thighs each evening, just before bed, for six weeks reduced the frequency and intensity of cramps compared to no stretching. An older trial, with calf stretches alone based on simple advice in patients taking quinine, had found no effect. Without risk and free, they deserve six weeks of regular trial.
When should calf pain be a cause for concern?
When the calf remains painful, swollen, warm or red after the episode, especially after travel, immobilization or surgery: thrombophlebitis must be ruled out, without delay. When pain appears while walking and subsides when stopping, a possible sign of arterial disease. When cramps are accompanied by weakness, muscle wasting or affect many muscles. And when they appeared with a new medication.
What to remember about calf cramps?
That it stops by stretching the calf, toes toward you. That it is common, often nocturnal, and most often without disease. That certain medications clearly promote it, to be reviewed with your doctor. That evening stretches and, according to a recent trial, vitamin K2 prevent it, that magnesium helps especially when intake is insufficient, and that quinine has been abandoned. And that a swollen and warm calf is not a cramp.
Sources
The studies cited below were identified via PubMed.
- Naylor JR, Young JB. General population survey on rest cramps. Age and Ageing, 1994;23(5):418-420. DOI
- Allen RE, Kirby KA. Nighttime leg cramps. American Family Physician, 2012;86(4):350-355. PubMed
- Garrison SR, Dormuth CR, Morrow RL, Carney GA, Khan KM. Nighttime cramps and preceding prescriptions: sequence symmetry analysis. Archives of Internal Medicine, 2012;172(2):120-126. DOI
- Schwellnus MP, Drew N, Collins M. Running speed and history of cramps, rather than dehydration or sodium, predict exercise-related cramps: prospective cohort of 210 Ironman triathletes. British Journal of Sports Medicine, 2011;45(8):650-656. DOI
- Hallegraeff JM, van der Schans CP, de Ruiter R, de Greef MH. Stretching before bedtime reduces the frequency and intensity of nighttime cramps in older adults: randomized trial. Journal of Physiotherapy, 2012;58(1):17-22. DOI
- Coppin RJ, Wicke DM, Little PS. Nighttime cramps: calf stretches and quinine discontinuation, factorial randomized trial. British Journal of General Practice, 2005;55(512):186-191. PubMed
- Tan J, Zhu R, Li Y, et al. Vitamin K2 in the management of nocturnal cramps: a randomized clinical trial. JAMA Internal Medicine, 2024;184(12):1443-1447. DOI
- Garrison SR, Korownyk CS, Kolber MR, et al. Magnesium for muscle cramps. Cochrane Database of Systematic Reviews, 2020;9:CD009402. DOI
- Luo L, Zhou K, Zhang J, Xu L, Yin W. Treatments for leg cramps during pregnancy. Cochrane Database of Systematic Reviews, 2020;12:CD010655. DOI
- Chan P, Huang TY, Chen YJ, Huang WP, Liu YC. Double-blind, placebo-controlled randomized trial of B-vitamin complex for nocturnal cramps in elderly hypertensive individuals. Journal of Clinical Pharmacology, 1998;38(12):1151-1154. PubMed
- El-Tawil S, Al Musa T, Valli H, et al. Quinine for muscle cramps. Cochrane Database of Systematic Reviews, 2015;(4):CD005044. DOI
