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 2,400 mg a day most trials used.^{1, 6} Pooled trials found no rise in serious adverse events, hypoglycaemia or liver enzymes, but three groups must not take it: 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. The safety spoke of the Wellgard berberine guide.

Sources checked on 30 October 2026.

What are the side effects of berberine?

The organ berberine is hard on is the gut, which is where most of it stays: oral absorption was under 1% in rats and human blood levels are in the low nanograms per millilitre.⁴ In the 18 lipid trials pooled in 2023 no serious adverse event occurred, and the 409-person PREMOTE trial saw more gut symptoms on berberine than placebo.^{1, 5} Constipation, diarrhoea and nausea are the named effects, and across 37 glucose trials total adverse events did not rise.^{1, 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, 19}

How do you get past the stomach effects?

Do what the trials did. The trials gave berberine in two or three doses a day; one capsule with a meal is the gentlest start, and if a label says several a day, spread them across meals.^{5, 6} The trials did not time how long wind and loose stools last; if they persist, 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 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.⁴ Metformin alone rarely causes hypos, and a 2025 study of goldenseal (a berberine-containing plant) with metformin found no clinically meaningful change in metformin levels overall; 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 head-to-head trials; berberine with or after the weight-loss injection covers 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, and in 10 trials of 811 people with non-alcoholic fatty liver disease both enzymes fell on berberine.^{10, 11} Three regulator-recorded cases of raised liver enzymes (one in Canada, two in the US on a multi-ingredient product), none with a link established, and one grade 3 enzyme rise among 12 people in a colitis trial are the whole of the human liver signal.^{16, 19} Constant pain under the right ribs with yellowing skin or eyes, dark urine, pale stools or itching is a GP visit that day. People with G6PD deficiency, an inherited enzyme shortage, are advised to avoid berberine because of a haemolysis risk.³ The full record is on is berberine bad for your kidneys or liver.

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's 2019 opinion also advises children, adolescents and people with diabetes or liver or heart conditions not to take berberine supplements.^{2, 19} That rules it out for anyone trying to conceive, including readers with polycystic ovary syndrome (PCOS, now called PMOS by the NHS): stop it before you might be pregnant, and treat a late period as a reason to test. The PCOS trials are on berberine for PCOS; anyone on the pill or in fertility treatment asks their clinic first.

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).^{12, 13} Tell your pharmacist; what medicines interact with berberine goes medicine by medicine. Finally, anyone with a heart-rhythm problem: berberine blocks a cardiac potassium channel in the laboratory, the French agency notes a torsades de pointes risk with intravenous berberine in heart failure, and one published case describes a slow heart rate after starting a berberine product, so palpitations or fainting mean stop and see a GP.^{3, 4, 19, 20}

Does berberine affect mood, sleep, headaches, heart rate or how often you pee?

Reported, not trialled. Forums describe both ends, "euphoric" and "seriously low" mood, better sleep and insomnia, headaches, dizziness and a racing heart; no trial measured any of them, so there is no rate to quote. The French agency's 2019 opinion records one nutrivigilance case of headache and dizziness at 500 mg a day, judged possibly linked.¹⁹ 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 many antidepressants, a change in how an antidepressant feels is a pharmacist conversation, never a reason to alter its dose.¹³ No trial reports a change in how often people pass urine; anything new is a GP conversation.

Is berberine safe to take, and for how long?

One trial ran two years at 600 mg a day after bowel-polyp removal, with constipation in 1% and no serious events; at the 900 to 2,400 mg a day most trials used, the longest ran about six months.^{17, 1, 6} Take it for a reason you can measure, review at 12 weeks, and report a suspected reaction to your local authority's trading standards or environmental health team, which works with the Food Standards Agency.¹⁴

What we don't know

How long the gut effects last: no trial timed them.¹ Whether berberine affects mood, sleep, heart rate or urination: no trial has measured any of them. Whether it is safe beyond two years at 600 mg a day, or beyond about six months at 900 to 2,400 mg: no trial has run longer.^{17, 1, 6} Whether it is safe with alcohol: untested.

Frequently asked questions

Can too much berberine be harmful?

Gut side effects rise from about 900 mg a day, and in trials above 2 g a day the glucose effect was no longer significant, so stay inside a label dose and never double up.^{7, 18, 19}

Is berberine safe for kidneys?

None of the trials reported kidney harm; the caution is for transplant patients on ciclosporin, whose trough levels were 29% higher, and on tacrolimus, cleared by the same enzyme.^{12, 13} Is berberine bad for your kidneys or liver has the full record.

Can berberine cause constipation, or make you poo more often?

Both directions are reported, at the rates above.¹ Berberine and gut health has the full picture.

Can you drink alcohol while taking berberine?

No trial has tested the pair. Both are handled by the liver, so the general caution applies. Keep inside the NHS low-risk guideline, "not more than 14 units a week on a regular basis".¹⁵

Sources

1. Blais JE, Huang X, Zhao JV. Drugs, 2023. Meta-analysis, 18 placebo-controlled trials, 1,788 adults; funding not stated on PubMed. PubMed 36941490.
2. Chan E. Displacement of bilirubin from albumin by berberine. Biology of the Neonate, 1993. Laboratory and rat study. PubMed 8513024.
3. Rad SZK, Rameshrad M, Hosseinzadeh H. Iranian Journal of Basic Medical Sciences, 2017. Narrative toxicology review. PubMed 28656087.
4. Dumitru CN, et al. Berberine-drug interactions. Pharmaceuticals, 2026. Narrative review; no conflicts declared. 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. Randomised trial, 409 adults with type 2 diabetes, 12 weeks; no competing interests declared. PubMed 33024120.
6. Xie W, et al. Glucose-lowering effect of berberine on type 2 diabetes. Frontiers in Pharmacology, 2022. Meta-analysis, 37 randomised trials, 3,048 adults; no commercial funding declared. PubMed 36467075.
7. Lan J, et al. Journal of Ethnopharmacology, 2015. Meta-analysis, 27 randomised trials, 2,569 adults; funding not stated on PubMed. PubMed 25498346.
8. Nguyen JT, et al. Clinical and Translational Science, 2025. Crossover study, adults with type 2 diabetes on metformin; no conflicts declared. PubMed 39943692.
9. NHS. Low blood sugar (hypoglycaemia). Page last reviewed 3 August 2023 (review was due 3 August 2026). Read 30 October 2026. nhs.uk/conditions/low-blood-sugar-hypoglycaemia.
10. Asbaghi O, et al. Clinical Nutrition ESPEN, 2020. Meta-analysis, 12 randomised trials; no conflicts declared. PubMed 32690176.
11. Nie Q, et al. Journal of Translational Medicine, 2024. Meta-analysis, 10 randomised trials, 811 people with fatty liver; no competing interests declared. PubMed 38429794.
12. Wu X, et al. European Journal of Clinical Pharmacology, 2005. Controlled trial, 52 against 52 transplant recipients, 3 months; funding not stated on PubMed. PubMed 16133554.
13. Guo Y, et al. Repeated administration of berberine inhibits cytochromes P450 in humans. European Journal of Clinical Pharmacology, 2012. Crossover study, healthy men, 2 weeks; no conflict declared. PubMed 21870106.
14. Food Standards Agency. How to report a food safety or hygiene issue for members of the public. Page updated 5 August 2026. Read 30 October 2026. gov.uk.
15. NHS. Alcohol units. Page last reviewed 27 August 2024. Read 30 October 2026. nhs.uk/live-well/alcohol-advice/calculating-alcohol-units.
16. Xu L, et al. Cancer Prevention Research, 2020. Randomised phase I trial, 16 people with ulcerative colitis, 3 months; funding not stated on PubMed. PubMed 31619442.
17. Chen YX, et al. Lancet Gastroenterology and Hepatology, 2020. Randomised trial, 1,108 adults, up to 2 years; Chinese state research funding. PubMed 31926918.
18. Liang Y, et al. Endocrine Journal, 2019. Meta-analysis, 28 trials, 2,313 people with type 2 diabetes; funding not stated on PubMed. PubMed 30393248.
19. ANSES. Opinion on the safety of berberine-containing plants in food supplements, saisine 2018-SA-0095. Agency opinion, in French, 1 August 2019. anses.fr.
20. Cannillo M, et al. Berberine behind the thriller of marked symptomatic bradycardia. World Journal of Cardiology, 2013. Case report, 1 man. PubMed 23888197.

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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.