Berberine side effects

What are the common side effects of berberine?

In the 2012 type 2 diabetes meta-analysis, the reported adverse effects were mostly digestive: constipation, diarrhea, nausea and abdominal bloating; there was no significant difference in adverse effect frequency between the berberine and control groups, and no serious adverse effects were observed. In some trials it was reported that constipation resolved when the dose was reduced. ^[1] In the 2022 meta-analysis covering 37 trials and 3,048 patients, the overall frequency of adverse effects did not increase when berberine was used alone or together with oral antidiabetic drugs; because the interval stayed below 1, adverse effects were reported less often in the berberine arm (RR 0.73; 95% CI 0.55–0.97; p=0.03). ^[2] In the lipid meta-analysis too, the frequency of adverse effects did not differ significantly between groups (RR 0.64; 95% CI 0.31–1.30) and no serious adverse effects were reported. ^[3]

Limit: the authors have reported limitations regarding the methodological quality of the trials entering these meta-analyses; long-term safety cannot be derived from these data. ^[3]

Does berberine lower blood sugar too much?

In type 2 diabetes trials, when berberine was used alone or with oral antidiabetic drugs, the risk of hypoglycemia did not increase significantly (RR 0.48; 95% CI 0.21–1.08); however, the certainty of the evidence for this result was rated very low. ^[2] The drug interaction review, on the other hand, reports that berberine may carry risks of hypoglycemia, hypotension and QT prolongation on the pharmacodynamic additive axis; this is a mechanism-based warning, and documented interaction pairs in humans are limited. ^[7] This warning applies especially to people using drugs that lower blood sugar; adjusting medication is a physician’s decision.

Which drugs does berberine interact with?

The review summarizes berberine’s interaction potential on four axes: inhibition and transcriptional induction of CYP3A4 (together with inhibition of CYP2D6 and CYP2C9); transporters (P-glycoprotein, OCT1/OCT2, MATE1); pharmacodynamic additive effects; and gut microbiota-derived effects (not proven, a candidate axis). The authors state that although systemic exposure is very low, high local concentrations in the gut and liver create interaction potential, and that few pairs are documented in humans, most being mechanism-based. ^[7]

Three points should be noted. First, goldenseal extract is not pure berberine; it also contains other alkaloids, so this study cannot be counted as direct evidence for a pure berberine supplement. Second, in the cyclosporine study in healthy volunteers the effect varied with dose; no significant change was found with 6 mg/kg cyclosporine. In contrast, in kidney transplant recipients using cyclosporine, the level was shown to rise markedly; the authors attributed the interaction most likely to CYP3A4 inhibition. ^[10] Third, simulation data are not clinical evidence, and the authors state that the findings need to be confirmed by controlled interaction studies. ^{[4] [5] [6]}

The metformin finding is important in terms of direction: in these data, goldenseal extract did not increase but decreased metformin exposure. RCTs in type 2 diabetes that add berberine to drugs such as metformin answer a separate question and report benefit; these are covered on the berberine benefits page. ^[1]

Is berberine safe in pregnancy and in newborns?

In Chan’s 1993 study, berberine was found to be about ten times stronger than phenylbutazone and about a hundred times stronger than papaverine, on a molar basis, in displacing bilirubin from serum albumin (in vitro). One week of daily intraperitoneal administration to adult rats significantly reduced serum bilirubin binding, and a lasting rise in free and total bilirubin levels was seen. The authors recommended avoiding the use of herbal products with a high berberine content in jaundiced newborns and pregnant women. The article also mentions the risk of kernicterus associated with huanglian (Coptis chinensis) in jaundiced Chinese newborns. ^[8]

These are laboratory and animal data. The US National Center for Complementary and Integrative Health (NCCIH) states that goldenseal, which contains berberine, should not be used by pregnant and breastfeeding women and should not be given to infants, and that the berberine in goldenseal may be harmful to newborns. ^[11] The same source states that the study in which goldenseal extract lowered metformin level by about 25% was of a size that could impair blood sugar control in people with type 2 diabetes taking metformin. ^[11]

Does berberine harm the liver?

According to NIH LiverTox, berberine has not been associated with serum transaminase elevations or clinically apparent liver injury during treatment; the likelihood score is E (unlikely cause of liver injury). The same source notes that there are few prospective studies in humans that report laboratory results in detail and that the frequency of hypersensitivity reactions is not known. ^[9]

Who should avoid berberine or consult a physician?

• Pregnant and breastfeeding women, infants and jaundiced newborns: the finding of bilirubin displacement and the NCCIH warning. ^{[8] [11]}
• People using drugs with a narrow therapeutic range, such as cyclosporine: in healthy volunteers a single 0.3 g berberine raised the AUC of 3 mg/kg cyclosporine by 19.2%, and no significant change occurred in the 10-day arm with 6 mg/kg cyclosporine; in kidney transplant recipients the trough level was 29.3% higher than in the control group and AUC rose by 34.5% in the pharmacokinetic part. ^{[4] [10]}
• People using drugs that are substrates of CYP3A4, CYP2D6, P-glycoprotein or transporters: mechanism-based interaction risk. ^[7]
• People using blood sugar-lowering drugs: additive effect and change in metformin exposure. ^{[5] [2]}
• People using regular medication: the review emphasizes that berberine use should be asked about when reviewing the medication list. ^[7]

Product quality is also an uncertainty: the review states that in non-standardized products the actual dose taken is uncertain and that national limits in the EU differ by more than tenfold. ^[7] This guide does not set personal doses or drug intervals; the drug’s package insert, the physician and the pharmacist take precedence.