Berberine

What is berberine?

Berberine is an isoquinoline alkaloid found in plants such as Berberis species, Coptis chinensis and Hydrastis canadensis (goldenseal). ^[10] Supplements may contain pure berberine or extracts of these plants; the review notes that the quality of non-standardized products makes the actual dose taken uncertain. ^[10]

One review reports that systemic exposure after oral berberine is very low (oral bioavailability 0.68% in rats; plasma levels in humans in the ng/mL range), yet it reaches high local concentrations in the gut and liver and carries interaction potential. ^[10]

Does berberine lower blood sugar in type 2 diabetes?

The 2021 meta-analysis by Guo and colleagues examined 46 RCTs comparing berberine, alone or together with standard diabetes treatment, with a control group; eight databases, including Chinese databases, were searched. Significant decreases were reported in HbA1c (mean difference −0.73; 95% CI −0.97 to −0.51), fasting plasma glucose and 2-hour glucose, as well as reductions in fasting insulin, HOMA-IR and BMI. ^[2]

There are limits: the 2012 meta-analysis of 14 RCTs (1,068 people) stated that methodological quality was generally low, samples small, the number of trials limited and the risks of bias unclear, and said that the evidence should be interpreted with caution. ^[1] The authors of the 37-trial 2022 meta-analysis rated the certainty of the fasting glucose and HbA1c finding as ‘moderate’ with GRADE (downgraded by one level for risk of bias). ^[12] In these trials berberine was generally used in the range of 0.5–1.5 g per day, in two to three divided doses; this is a trial design, not a recommendation. ^[1] Evidence grade: B (consistent decrease across multiple meta-analyses; trial quality limited, certainty moderate at best).

Is berberine ‘nature’s metformin’?

This comparison is often used; the evidence does not support superiority to or equivalence with metformin. In the 14-RCT meta-analysis above, when berberine was compared with oral antidiabetics such as metformin, glipizide or rosiglitazone, berberine did not show significantly better glycemic control; the authors stated that these results should be interpreted with caution because of low quality, small samples and unclear risks of bias. ^[1] In the same meta-analysis, using berberine together with the same drug showed better glycemic control than the drug alone; this advantage comes from trials on adding berberine to a drug, not on berberine replacing the drug. ^[1]

A result of ‘no superiority’ also does not mean ‘equivalent’: because quality is low, equivalence has not been proven. Metformin and other antidiabetics are prescription drugs; there are no data showing that using berberine in their place is safe. Evidence grade: E (superiority not shown).

Does berberine lower blood sugar too much?

In a 2022 meta-analysis covering 37 trials and 3,048 patients, berberine lowered fasting glucose by 0.82 mmol/L, HbA1c by 0.63 percentage points and 2-hour glucose by 1.16 mmol/L; when berberine was used alone or with oral antidiabetics, the risk of hypoglycemia did not increase significantly (RR 0.48; 95% CI 0.21–1.08). ^[12] However, the certainty of the evidence for this hypoglycemia result was rated very low. ^[12] A drug interaction review, on the other hand, reports that berberine may carry a pharmacodynamic additive risk of hypoglycemia, hypotension and QT prolongation; this is a mechanism-based warning. ^[10] For people using blood sugar-lowering drugs, this is a matter to discuss with a physician before berberine is added.

How should the berberine evidence be read?

A common feature of berberine meta-analyses is that a small number of small trials are pooled many times, and some of these trials come from Chinese databases. The 2012 meta-analysis reported that methodological quality was generally low, and the 2018 lipid meta-analysis reported weakness in random sequence generation, allocation concealment, blinding and missing data, and high clinical heterogeneity. ^{[1] [3]} Results such as ‘HbA1c fell’ or ‘LDL fell’ therefore indicate a direction but their size is not certain; and a fall in a laboratory value does not mean that heart attacks or diabetes complications are reduced; the meta-analyses examined did not measure these clinical outcomes.

Does berberine lower cholesterol?

The 2018 meta-analysis by Ju and colleagues had 2,147 participants in 16 RCTs. Berberine lowered total cholesterol (−0.47 mmol/L; 95% CI −0.64 to −0.31), LDL cholesterol (−0.38 mmol/L; 95% CI −0.53 to −0.22) and triglycerides (−0.28 mmol/L; 95% CI −0.46 to −0.10); when used alone, HDL cholesterol rose slightly (+0.08 mmol/L). The included trials showed high clinical heterogeneity, and the methodological quality of most was low in random sequence generation, allocation concealment, blinding and missing data; no serious adverse effects were reported. ^[3] Evidence grade: C.

Does berberine help with weight loss?

In the 12-RCT meta-analysis by Asbaghi and colleagues, berberine reduced body weight by an average of 2.07 kg (95% CI −3.09 to −1.05), BMI by 0.47 kg/m², waist circumference by 1.08 cm and CRP by 0.42 mg/L; no significant effect was seen on ALT and AST. ^[4] The effect is small, and the participants in most trials were studied for metabolic disease, not for weight loss. Evidence grade: C.

Does berberine work in PCOS?

In the 12-RCT meta-analysis by Xie and colleagues, the live birth rate with berberine was similar to placebo and metformin and lower than with letrozole (RR 0.61; 95% CI 0.44–0.82); the authors concluded that there was no robust evidence that berberine improves live birth or other clinical outcomes. Decreases were seen in total testosterone and the LH/FSH ratio relative to placebo or no treatment; compared with metformin, total cholesterol, waist circumference and waist-to-hip ratio were lower, and BMI did not differ. ^[5] The evidence grade is C for hormonal and metabolic indicators and E for live birth.

Is berberine safe? Side effects, drug interactions and pregnancy

Digestive side effects. In meta-analyses, the common adverse effects in the berberine groups are digestive (constipation, diarrhea, nausea, abdominal bloating); no serious adverse effects have been reported. ^[1] In the Ju meta-analysis, adverse effect frequency did not differ significantly between groups. ^[3]

Liver. According to NIH LiverTox, berberine has not been associated with transaminase elevations or clinically apparent liver injury during treatment (likelihood score E: unlikely cause of liver injury); it is also noted that this judgment rests on the small number of prospective studies in humans that report laboratory results in detail. ^[9]

Drug interactions. In two small studies in healthy men (6 people each), berberine affected cyclosporine levels: a single 0.3 g dose of berberine with 3 mg/kg cyclosporine raised AUC by 19.2%; with 6 mg/kg cyclosporine for 10 days, 0.3 g berberine twice daily produced no significant change. ^[6] A goldenseal extract standardized to berberine raised the AUC of the CYP3A substrate midazolam 1.43-fold in 16 healthy volunteers and lowered metformin AUC to 0.77-fold; this extract is not pure berberine. ^[7] A review summarizes from these and similar data the axes of CYP3A4, CYP2D6, transporters (P-glycoprotein, OCT1/OCT2, MATE1) and pharmacodynamic addition (hypoglycemia). ^[10] For details, see the berberine side effects and drug interactions page.

Pregnancy and newborns. In Chan’s 1993 study, berberine was found to be about ten times stronger than phenylbutazone in displacing bilirubin from albumin binding (in vitro, on a molar basis), and when given to adult rats by intra-abdominal injection every day for one week it significantly reduced serum bilirubin binding. The authors stated that the use of plants with a high berberine content in jaundiced newborns and pregnant women should be avoided. ^[8] This finding is laboratory and animal data; the article mentions reports of kernicterus risk associated with a berberine-containing plant in jaundiced Chinese newborns. The US NCCIH warning about goldenseal and breastfeeding is reported separately on the side effects page.

Is berberine legal in Türkiye?

In Türkiye, each food supplement must be approved by the Ministry of Agriculture and Forestry. ^[11] In the Ministry’s Plant List (updated 16/07/2026), the root and root bark of kadın tuzluğu (barberry, Berberis vulgaris) and Berberis aquifolium are listed as negative (N) and the fruits as positive (P); goldenseal (Hydrastis canadensis) root and root extract are positive. ^[13] The approval status of an individual product can be understood from the Ministry’s approval records. For the EU, a review reports that the regulatory framework for berberine is not settled and that national limits differ by more than tenfold. ^[10]

Summary of the evidence

What questions should be asked when considering a supplement?

For what outcome would it be used: treating a disease such as type 2 diabetes is a physician’s task; berberine cannot be used in place of a drug. Is regular medication being used: drugs with a narrow therapeutic range such as cyclosporine, and blood sugar-lowering drugs, require special attention. Is there pregnancy, breastfeeding or a newborn: in these situations it is considered a product to be avoided. According to the Ministry, presenting food supplements as if they were products that prevent or treat diseases is contrary to the regulations. This guide does not recommend personal doses; the decision on use should be made together with a physician and pharmacist.