Berberine side effects and drug interactions
Berberine’s most common side effects are digestive — constipation, diarrhoea and cramping. Its more important risk is interactions: in a clinical study, two weeks of berberine 300 mg three times daily reduced the activity of three major drug-metabolising liver enzymes (CYP2D6, CYP2C9 and CYP3A4), which can raise blood levels of many medicines. It can also add to diabetes medicines, and it should not be used in pregnancy, breastfeeding or infants.
This article answers one question. For what Berberine is, where it comes from and its other uses, see the Berberine ingredient guide.
Key findings
- Repeated berberine dosing inhibited CYP2D6, CYP2C9 and CYP3A4 in healthy volunteers.
- Combining berberine with glucose-lowering medicines can increase the risk of low blood sugar.
- Berberine should not be used in pregnancy, breastfeeding or in infants.
- Digestive side effects are the most commonly reported adverse effects.
What human research shows about interactions
In a randomised crossover study of healthy men, researchers gave berberine 300 mg three times daily for two weeks and then used standard probe drugs to measure enzyme activity (Guo et al., Eur J Clin Pharmacol 2012). Compared with the control phase, the dextromethorphan urinary ratio rose about ninefold (reduced CYP2D6 activity), the losartan metabolite ratio doubled (reduced CYP2C9 activity), and midazolam exposure increased by around 40% (reduced CYP3A4 activity). These enzymes metabolise a large share of prescription medicines, so inhibition can raise drug levels and side effects. The Endotext (NCBI Bookshelf) review also highlights berberine’s inhibition of drug-metabolising enzymes as a reason for caution with multiple medicines.
Evidence table
| Study or source | Population | What was tested | Main result | Limitations |
|---|---|---|---|---|
| Guo et al., Eur J Clin Pharmacol 2012 | Healthy men (crossover) | Berberine 300 mg three times daily for 2 weeks; probe drugs | CYP2D6 ↓ (dextromethorphan ratio ~9×), CYP2C9 ↓ (losartan ratio ~2×), CYP3A4 ↓ (midazolam AUC ~+40%) | Small; healthy volunteers; single regimen |
| ClinicalTrials.gov NCT02365480 protocol | Summary of earlier clinical use | Oral doses up to 1,500 mg/day, up to 3 months | Mild–moderate constipation in 3–8% | Background summary |
| NCCIH berberine page | Safety guidance | — | Not for pregnancy, breastfeeding or infants; discuss with provider if taking medicines | Guidance summary |
Common side effects
- Constipation, diarrhoea, abdominal cramping and wind. A clinical trial protocol summarising earlier studies reported mild to moderate constipation in 3–8% of participants at doses up to 1,500 mg a day (ClinicalTrials.gov NCT02365480 protocol).
- Nausea or stomach discomfort, often reduced by taking it with food.
Medicines to check with a pharmacist
- Diabetes medicines (insulin, sulfonylureas, metformin and others): additive glucose lowering; monitor for low blood sugar.
- Medicines metabolised by CYP3A4, CYP2D6 or CYP2C9: examples of affected drug classes include some sedatives, some antidepressants and antipsychotics, some blood-pressure medicines and some anticoagulants. The probe-drug study shows the enzymes are affected; it does not list every medicine at risk.
- Medicines with a narrow safety margin, where small changes in blood levels matter.
- Other glucose-lowering supplements such as chromium, bitter melon, gymnema or alpha-lipoic acid.
Who should avoid berberine or seek advice first
- Pregnant or breastfeeding people and infants — berberine has been linked to harmful bilirubin build-up in infants (NCCIH berberine page).
- Anyone taking regular prescription medicines.
- People with liver disease.
- People with a history of low blood sugar.
Limitations
- The enzyme study was small, in healthy men, and used one dose over two weeks.
- Probe-drug changes indicate risk but do not quantify effects for each medicine.
- Supplement berberine content varies, which changes exposure.
Practical label reading
- Look for berberine listed in milligrams; plant extracts such as goldenseal, barberry or Oregon grape also contain it.
- Check multi-ingredient blood sugar products for hidden berberine.
- Take the full label to a pharmacist if you take any regular medicine.
Related: berberine evidence review · berberine dosage for blood sugar · berberine guide
Frequently asked questions
Does berberine interact with medications?
Yes. It reduced the activity of CYP2D6, CYP2C9 and CYP3A4 in a human study and can add to diabetes medicines.
Can I take berberine with metformin?
Only with your clinician’s agreement and glucose monitoring, because effects on blood sugar can add together.
What are the most common berberine side effects?
Digestive effects such as constipation, diarrhoea and cramping.
Is berberine safe in pregnancy?
No. It should not be used in pregnancy, breastfeeding or by infants.
Does goldenseal contain berberine?
Yes; goldenseal and several other plants contain berberine, so the same interaction concerns may apply.
References
- Guo et al., Eur J Clin Pharmacol 2012. Repeated administration of berberine inhibits cytochromes P450 in humans. Eur J Clin Pharmacol.
- Endotext (NCBI Bookshelf): complementary and integrative approaches for type 2 diabetes.
- NCCIH berberine page.
- ClinicalTrials.gov NCT02365480 protocol.