Berberine: Dangers, Side Effects and Interactions You Need to Know

Two levels must be distinguished. In published clinical trials, it is generally well tolerated: effects are essentially digestive, and a randomized trial against placebo on 1108 participants reported no serious adverse effects. But Anses, which evaluates over-the-counter sales conditions and not a controlled trial, concludes that there are established pharmacological effects and recommends that several populations not consume it. Both findings are accurate: they do not apply to the same situation.

Requested by the DGCCRF in April 2018, Anses published its opinion on November 25, 2019. It confirms established pharmacological effects from 400 mg per day, on blood pressure and heart rate, on the nervous system, on the immune system and on metabolism, without excluding that these effects exist at lower doses. It emphasizes that this dose is likely exceeded by many products on the French market.

Clinical literature does in fact provide an answer: berberine, in the form of ursodeoxycholate, is undergoing pharmaceutical development with Phase 2 trials published in JAMA Network Open and Nature Communications, and Phase 3 trials currently underway. One does not conduct such trials on a substance without effects. In France, it remains marketed as a dietary supplement without dose limits, which explains the Anses position and the very low ceiling set in Belgium.

That it is a substance with proven pharmacological effects, regulated by a health agency opinion, and not an ordinary supplement. That Anses recommends that several populations avoid consuming it, including people with diabetes, pregnant and nursing women, children and adolescents, and people suffering from liver or heart disorders. That drug interactions are numerous and documented. And that no health claims are authorized.

Anses recommends that children and adolescents, pregnant or nursing women, people with diabetes, and people suffering from liver or heart disorders should not consume berberine-based supplements. It also advises against these supplements for people taking medications. The list is extensive and precisely covers part of the audience these products typically target.

This is the central paradox of this issue. Berberine is most often consumed to regulate blood sugar levels, yet Anses specifically recommends that people with diabetes not take it. The reason lies in the risk of hypoglycemia and interactions with antidiabetic treatments, with metformin being explicitly cited. In other words, the population most commercially targeted is the one the agency excludes.

No. Anses recommends that pregnant or nursing women should not consume berberine-based supplements, and French regulations already require that labeling of these products bear a warning discouraging their use by pregnant women. This is one of the rare situations where a warning statement is explicitly required on the label.

No. Anses explicitly recommends that children and adolescents should not consume berberine-based supplements. This recommendation has no exceptions in a self-medication context, and any metabolic concerns in a young person warrant medical advice, not a supplement purchased online.

Anses specifically cites carbamazepine, cyclosporine, digoxin, losartan, and metformin. Regarding data, a systematic review of 66 clinical interaction studies concludes that at common doses berberine is not a potent or moderate cytochrome inhibitor, but does show a weak effect on CYP3A4 and CYP2D6. An animal study using cyclosporine as a probe, however, measured an exposure reduction of over half, which poses primarily a risk of treatment failure.

It designates a medication where the gap between the effective dose and the problematic dose is small. For these treatments, even a modest variation in blood concentration can tip from insufficient effect to excessive effect. This is precisely what an interaction can cause, which is why cases reported internationally predominantly concern this type of medication. Digoxin and cyclosporine are examples.

Trials are consistent: they are digestive disorders, with constipation and diarrhea leading, and their frequency depends on the dose. In the Lancet trial at 600 mg per day, constipation affected 1% of berberine participants versus less than 0.5% under placebo. In a trial at 1500 mg per day in people with diabetes, 34.5% experienced transient digestive disorders, with no observed liver or kidney damage. Anses adds risks of hypoglycemia and hypotension.

Marked or persistent digestive disorders, signs suggesting hypoglycemia such as tremors, sweating, or malaise, dizziness that may indicate hypotension, and especially yellowing of the skin or eyes, unusual fatigue, or dark urine, which warrant immediate medical consultation. Stop taking it and report the product, its dose, and duration.

Given the identified effects on blood pressure and heart rate, as well as the risk of hypoglycemia, definitely inform your medical team during the preoperative consultation and follow their instructions. The general rule applies here more than ever: mention your supplements when asked about your medications.

They do not answer the same question. A trial measures what happens to selected participants, often without heavy associated treatment, and biologically monitored. An agency evaluates what happens when the molecule is sold freely to people with diabetes or on treatment, at non-capped doses. A molecule well tolerated in one setting may pose problems outside that setting: this is the entire logic of the opinion.

In the 2008 trial in people with diabetes treated for three months at 1500 mg per day, no functional liver or kidney damage was observed. The meta-analysis on fatty liver reports only mild digestive effects. That said, one isolated French case associating jaundice and liver function abnormalities was documented by Anses, in a person consuming multiple products. Yellowing of the skin or eyes requires stopping and consulting a doctor.

Anses identifies proven pharmacological effects from 400 mg per day, while specifying that it is not excluded that these effects already exist at lower doses, which remains to be established. It especially emphasizes that this dose is likely exceeded by a large number of supplements present on the French market. So check the actual content per dose and per day.

No, no maximum daily dose is currently defined in France. The situation varies significantly across Europe: Belgium has set a maximum daily dose of 10 mg of isoquinoline alkaloids expressed as berberine, specifically to prevent these products from entering the drug category, while other countries authorize, restrict, or prohibit them.

No. No health claims are authorized at the European level, neither for berberine-containing plants nor for substances in the isoquinoline alkaloid group. This is a point Anses explicitly recalls. A brand displaying an effect on blood sugar, cholesterol, or weight therefore falls outside the regulatory framework, even if studies exist elsewhere.

This phrase circulates widely and is misleading in two ways. First, because it compares a dietary supplement to a prescribed and monitored medication with a different mechanism. Second, because it constitutes an unauthorized claim: no effect of this type can be asserted. Using this comparison to market amounts to promising a medicinal effect without the framework that should accompany it.