Berberine Side Effects: Who Should Avoid It and What to Expect

Berberine's side effects are mostly in the gut: constipation, diarrhoea, wind, nausea and stomach cramps, reported by 2 to 23% of people in placebo-controlled trials against 2 to 15% on placebo, and more often at the 900 to 1,500 mg a day the trials used.¹ Pooled trials found no rise in serious adverse events, hypoglycaemia or liver enzymes, but three groups must not take it at all: pregnant and breastfeeding women, anyone trying to conceive, and babies and children, because berberine frees bilirubin from its carrier protein and in a jaundiced newborn that can damage the brain.^{2, 3} People on insulin, gliclazide, transplant medicines or anticoagulants, and anyone with G6PD deficiency or a heart-rhythm or liver condition, need a pharmacist or GP first. This is the safety spoke of the Wellgard berberine guide.

What are the side effects of berberine?

The organ berberine is hard on is the gut, which is also where most of it stays, since under 1% is absorbed.⁴ In the 18 lipid trials pooled in 2023, gut complaints ran at 2 to 23% on berberine against 2 to 15% on placebo, with no serious adverse event in any trial, and the 409-person PREMOTE trial saw more gut symptoms on berberine than placebo.^{1, 5} Constipation is as common as diarrhoea; nausea, bloating, cramps and a bitter aftertaste make up the rest; across 37 glucose trials total adverse events did not rise.⁶ They are dose-related: the pooled analysis the French food-safety agency relied on found them more frequent from about 900 mg a day, settling when the dose was reduced.⁷

How do you get past the stomach effects?

Do what the trials did. Every outcome trial gave berberine in two or three doses with meals, never one large dose on an empty stomach; one capsule with a meal is the gentlest start, and if a label says several a day, spread them across meals.^{5, 6} The wind and loose stools usually fade within a fortnight; if not, drop to the lowest label dose or stop. Diarrhoea lasting more than a few days, blood in the stool, vomiting or pain that wakes you mean stop and see a GP. How to take berberine covers timing, forms and duration.

Can berberine cause a hypo?

On its own, rarely: in 37 pooled diabetes trials hypoglycaemia was no more common on berberine than placebo, because its effect on insulin release appears to need raised glucose.⁶ The risk is additive. Insulin, gliclazide and glimepiride lower glucose whether or not it is high, and berberine on top can tip a reading into a hypo, which is what the forum reports describe in people who added it to insulin or a sulfonylurea without telling their team.⁴ Metformin rarely causes hypos by itself, and a 2025 study of goldenseal (a berberine-containing plant) with metformin found no meaningful rise in metformin levels; the concern there is the combined glucose effect.⁸ If you take any glucose-lowering medicine, tell your diabetes team first, check your meter more often for a fortnight, and never adjust a dose yourself; the NHS hypoglycaemia page sets out the symptoms and what to do.⁹ Berberine vs metformin covers the one head-to-head trial and why swapping is not an option, and berberine with or after the weight-loss injection covers the low readings people describe when combining the two.

Is berberine bad for your liver or kidneys?

For the liver, the trial data point the other way. Across 12 randomised trials berberine did not change ALT or AST, the enzymes a liver blood test measures, and in 10 trials of 811 people with non-alcoholic fatty liver disease both enzymes fell on berberine.^{10, 11} A couple of case reports of raised liver enzymes, in which the link was not established, are the whole of the human liver signal; European food-safety regulators have been reviewing berberine's safety data during 2026. The "my liver hurts" post is almost always the gut: pain under the right ribs after starting berberine is usually trapped wind that moves and eases with a bowel movement. Constant pain with yellowing skin or eyes, dark urine, pale stools or itching is a GP visit that day. For the kidneys there is no signal in the trials; the caution is for transplant patients, because ciclosporin and tacrolimus levels rose by about a third.¹² People with G6PD deficiency, an inherited enzyme shortage common in people of African, Mediterranean, Middle Eastern and South Asian heritage, are advised to avoid berberine because of a haemolysis risk described in laboratory and historical reports.³

Who should not take berberine?

Berberine displaces bilirubin from its carrier protein, which is why it is avoided in pregnancy, breastfeeding and infancy: in a jaundiced newborn the freed bilirubin can damage the brain; the French food-safety agency also advises children, adolescents and people with diabetes or liver or heart conditions not to take berberine supplements.^{2, 3} That rules it out for anyone trying to conceive, including readers with polycystic ovary syndrome who meet berberine as a metformin alternative: stop it before you might be pregnant, and treat a late period as a reason to test. It rules it out while breastfeeding too, so the postpartum reader weighing berberine against a prescribed medicine after gestational diabetes has one option, and the medicine is the GP's call. In small pooled PCOS trials berberine performed similarly to metformin on insulin resistance and testosterone measures, and anyone on the pill or in fertility treatment asks their clinic first.¹³

Then the medicine list. Ciclosporin and tacrolimus, warfarin and the newer anticoagulants, statins, many antidepressants, beta-blockers and calcium-channel blockers pass through enzymes that two weeks of berberine slows (CYP3A4, CYP2D6, CYP2C9); insulin and the sulfonylureas add their glucose-lowering to berberine's.^{12, 14} Tell your pharmacist; what medicines interact with berberine goes medicine by medicine in UK names. Finally, anyone with a heart-rhythm problem: berberine blocks a cardiac potassium channel in the laboratory, intravenous berberine caused dangerous rhythms in a small 1980s study, and one case of a slow heart rate after a berberine product is published, so palpitations or fainting mean stop and see a GP.^{3, 4}

Does berberine affect mood, sleep, headaches or heart rate?

Reported, not trialled. Forums describe both ends, "euphoric" and "seriously low" mood, better sleep and insomnia, headaches, dizziness and a racing heart, in roughly one in six berberine threads; no trial measured any of them, so there is no rate to quote and no way to separate berberine from a diet started the same week or a hypo. France's nutrivigilance system recorded a handful of headache and dizziness cases at 500 mg a day judged possibly linked.³ Low mood with a new supplement is a reason to stop it and talk to someone. And because berberine slows CYP2D6, the enzyme that clears sertraline, citalopram and most other antidepressants, a change in how an antidepressant feels is a pharmacist conversation, never a reason to alter its dose.¹⁴

Is berberine safe to take long term?

Nobody can say: the longest trials ran about six months, most three.^{1, 6} Within that window the pooled trials saw gut symptoms and nothing serious; beyond it there is no human data either way, so the answer is "unknown". Take it for a reason you can measure, review at 12 weeks, and report suspected side effects through the MHRA Yellow Card scheme, which covers supplements too.¹⁵

Frequently asked questions

Can berberine cause diarrhoea?

Yes, and constipation just as often; both are dose-related and usually settle within a fortnight when taken with meals in divided doses.^{1, 7}

Can too much berberine be harmful?

Gut side effects rise from about 900 mg a day and no trial has tested more than 1,500 mg, so stay inside a label dose and never double up.⁷

Is it bad to take berberine every day?

The trials gave it daily for up to six months without serious harm in the groups studied; the problem is who takes it, not the daily pattern.^{1, 6}

Is berberine safe for kidneys?

None reported in the trials; the caution is for transplant patients, because berberine raises ciclosporin and tacrolimus levels by about a third.¹²

Can you take berberine with metformin?

Only with your diabetes team's knowledge: metformin levels do not appear to change, but the two lower glucose together and their gut side effects stack.⁸

Sources

1. Blais JE, Huang X, Zhao JV. Overall and sex-specific effect of berberine for the treatment of dyslipidemia in adults: a systematic review and meta-analysis of randomized placebo-controlled trials. Drugs, 2023. PubMed 36941490.
2. Chan E. Displacement of bilirubin from albumin by berberine. Biology of the Neonate, 1993. PubMed 8513024.
3. Rad SZK, Rameshrad M, Hosseinzadeh H. Toxicology effects of Berberis vulgaris (barberry) and its active constituent, berberine: a review. Iranian Journal of Basic Medical Sciences, 2017. PubMed 28656087.
4. Dumitru CN, et al. Berberine-drug interactions: mechanisms, clinical relevance and risk stratification, a narrative review. Pharmaceuticals, 2026. PubMed 42653808.
5. Zhang Y, et al. Gut microbiome-related effects of berberine and probiotics on type 2 diabetes (the PREMOTE study). Nature Communications, 2020. PubMed 33024120.
6. Xie W, et al. Glucose-lowering effect of berberine on type 2 diabetes: a systematic review and meta-analysis. Frontiers in Pharmacology, 2022. PubMed 36467075.
7. Lan J, et al. Meta-analysis of the effect and safety of berberine in the treatment of type 2 diabetes mellitus, hyperlipemia and hypertension. Journal of Ethnopharmacology, 2015. PubMed 25498346.
8. Nguyen JT, et al. The pharmacokinetic interaction between metformin and the natural product goldenseal is metformin dose-dependent. Clinical and Translational Science, 2025. PubMed 39943692.
9. NHS. Low blood sugar (hypoglycaemia). nhs.uk/conditions/low-blood-sugar-hypoglycaemia.
10. Asbaghi O, et al. The effect of berberine supplementation on obesity parameters, inflammation and liver function enzymes: a systematic review and meta-analysis of randomized controlled trials. Clinical Nutrition ESPEN, 2020. PubMed 32690176.
11. Nie Q, et al. The clinical efficacy and safety of berberine in the treatment of non-alcoholic fatty liver disease: a meta-analysis and systematic review. Journal of Translational Medicine, 2024. PubMed 38429794.
12. Wu X, et al. Effects of berberine on the blood concentration of cyclosporin A in renal transplanted recipients: clinical and pharmacokinetic study. European Journal of Clinical Pharmacology, 2005. PubMed 16133554.
13. Li MF, Zhou XM, Li XL. The effect of berberine on polycystic ovary syndrome patients with insulin resistance (PCOS-IR): a meta-analysis and systematic review. Evidence-Based Complementary and Alternative Medicine, 2018. PubMed 30538756.
14. Guo Y, et al. Repeated administration of berberine inhibits cytochromes P450 in humans. European Journal of Clinical Pharmacology, 2012. PubMed 21870106.
15. MHRA. Yellow Card: report a suspected side effect. yellowcard.mhra.gov.uk.

This article is general information, not medical advice. Berberine is not taken in pregnancy, while breastfeeding, when trying to conceive or by children; if you take any regular medicine, ask your pharmacist or GP before starting it, and never stop or change a prescribed medicine on the strength of a supplement.