Berberine and Gut Health: Diarrhoea, Constipation and the Microbiome

Berberine's commonest side effects are in the gut. In 18 placebo-controlled trials pooled in 2023, gut side effects affected 2 to 23% of people on berberine against 2 to 15% on placebo, and in the four-arm microbiome trial the berberine groups had more gut side effects.^{1, 2} Very little of a dose reaches the blood, so most of it acts in the gut, where the microbiome studies looked.³ The trials are in the Wellgard berberine guide.

Sources checked on 30 October 2026.

Why does berberine upset the stomach?

Because it stays there. A 2026 review puts human blood levels in the low nanograms per millilitre while concentrations in the gut wall are high.³ In the 2023 pooling, 12 of the 18 trials reported gut side effects, more often on berberine, and none serious.¹ Gut distress rises with the dose, which is why trials split the day's berberine into two or three portions.⁴

Can berberine cause diarrhoea?

Yes. The shorter, higher-dose trials record loose stools, nausea and discomfort: in a three-month trial of 0.5 g three times a day, 20 people (34.5%) had transient gut side effects, and an umbrella review of 11 meta-analyses lists constipation and diarrhoea as berberine's common side effects.^{5, 6} The NHS diarrhoea and vomiting page lists diarrhoea "for more than 7 days" and bloody diarrhoea among the reasons to call 111.⁷ If diarrhoea starts with berberine, stop taking it; if it continues, see a GP.

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

Both are recorded. Constipation was the commonest side effect in the longest trial, 1,108 adults taking 0.3 g twice a day or placebo for up to two years after bowel-polyp removal (table below).⁸ No trial has given berberine to relieve constipation; it is a recorded side effect, not a use. The NHS constipation page says "Speak to a pharmacist if diet and lifestyle changes are not helping."¹⁰

How long do bloating, wind, nausea and stomach pain last?

No trial timed them. The trials call them transient and found none serious across 4 to 24 weeks, which says they pass without saying when.^{1, 5} The steps the trials used are a smaller portion and a meal.⁴ The NHS constipation page lists being "regularly bloated", "blood in your poo" and losing weight without trying among the reasons to see a GP.¹⁰

Should you take berberine on an empty stomach?

No trial has compared an empty stomach with a meal. The trials split the dose: three times a day in the three-month trial, twice a day in the two-year trial, and with breakfast, lunch and dinner in the 2021 absorption pilot.^{4, 5, 8} Divided doses and timing are on how to take berberine.

What did the microbiome studies find?

A 2026 systematic review found seven randomised trials that sequenced stool samples.¹¹ PREMOTE (409 newly diagnosed adults with type 2 diabetes, 20 Chinese centres, 12 weeks) ran four arms: berberine, berberine with live cultures, live cultures alone and placebo. HbA1c fell 0.99 points on berberine and 1.04 with the two together, against 0.59 on placebo and 0.53 on live cultures alone, and the glucose effect was traced to berberine stopping one gut bacterium, Ruminococcus bromii, from converting a bile acid.² Across the seven trials the review found "enrichment of gamma-Proteobacteria and depletion of butyrate-producing taxa", concluded the shifts "were not uniformly favourable", and called the findings hypothesis-generating.¹¹

Does berberine kill the gut bacteria you want to keep?

It changes the mix, and nobody has measured what that means for health. PREMOTE's authors describe berberine as bacteriostatic, meaning it stops bacteria multiplying.² The trials record a shift in Bifidobacterium breve with berberine, alone or with live cultures, and fewer butyrate-producing bacteria overall.^{11, 12} No trial measured a harm or a benefit from that; the review says causal inference cannot be established, and the 2026 interactions review calls the microbiome "a candidate axis rather than a demonstrated one".^{3, 11}

What about IBS, SIBO, candida and parasites?

These are diagnosed conditions, and the evidence is thin. IBS: in one Chinese trial, 132 adults with diarrhoea-type IBS took berberine hydrochloride (400 mg a day in two doses) or placebo for eight weeks; diarrhoea, abdominal pain and urgency fell more on berberine.¹³ SIBO: a trial comparing berberine with the antibiotic rifaximin was registered in 2023 and had not reported on PubMed by 30 October 2026.¹⁴ Candida: we found no human trial; parasites: two 1970s reports in children with giardiasis, too old to guide anyone.^{18, 19} All are diagnosed and managed with a GP, not self-medicated.

Before you take berberine: the cautions

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.^{15, 21} It interacts with medicines: ciclosporin levels were 29% higher in 52 transplant recipients taking it, and two weeks of dosing slowed three liver enzymes in healthy men, an effect that does not switch off between doses, so spacing doses does not remove an interaction; ask a pharmacist.^{3, 16, 17} On a glucose-lowering medicine the diabetes team decides, because the effects add.³ The full list is on berberine side effects, with the medicines, kidneys and liver, pregnancy and breastfeeding and PCOS (now called PMOS by the NHS) on their own pages.

What we don't know

How long the gut effects last: no trial timed them, so "transient" is as precise as the record gets.^{1, 5} Whether berberine clears SIBO: a 2025 network meta-analysis (30 trials, 1,552 people) ranked it highest of 12 treatments but called the ranking hypothesis-generating, and the rifaximin trial had not reported.^{14, 20} Whether a meal reduces the gut effects: no trial has compared food with an empty stomach. Whether the shifts in gut bacteria matter for health: no trial has measured an outcome from them.¹¹

Frequently asked questions

Does berberine help with bloating?

No trial has measured bloating as a benefit; where it appears it is a side effect counted against berberine.^{1, 6}

Does berberine change the colour of your poo?

Berberine is a yellow alkaloid and most of a dose passes through unabsorbed, so a yellow tint is plausible, but no trial recorded stool colour.³

Can you take berberine with live cultures?

One trial has tested "berberine with probiotics": in PREMOTE the two berberine arms lowered HbA1c by similar amounts (figures above) and the abstract reports no test between them.² That is one trial's finding, not advice to combine them.

Sources

1. Blais JE, et al. Overall and sex-specific effect of berberine for the treatment of dyslipidemia in adults. Drugs, 2023. Meta-analysis, 18 placebo-controlled trials, 1,788 adults; funding not stated on PubMed. PubMed 36941490.
2. 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 newly diagnosed type 2 diabetes, four arms, 12 weeks; no competing interests declared. PubMed 33024120.
3. Dumitru CN, et al. Berberine-drug interactions. Pharmaceuticals, 2026. Narrative review; no conflicts declared. PubMed 42653808.
4. Moon JM, et al. Absorption kinetics of berberine and dihydroberberine and their impact on glycemia. Nutrients, 2021. Crossover pilot, 5 men; one author a paid adviser to a supplement company. PubMed 35010998.
5. Yin J, Xing H, Ye J. Efficacy of berberine in patients with type 2 diabetes mellitus. Metabolism, 2008. Pilot, two studies totalling 84 adults with type 2 diabetes, 0.5 g three times a day for 3 months; funding not stated on PubMed. PubMed 18442638.
6. Li Z, et al. Berberine and health outcomes: an umbrella review. Phytotherapy Research, 2023. Umbrella review, 11 meta-analyses of randomised trials; funding not stated on PubMed. PubMed 36999891.
7. NHS. Diarrhoea and vomiting. Page last reviewed 21 December 2023. Read 30 October 2026. nhs.uk/conditions/diarrhoea-and-vomiting.
8. Chen YX, et al. Berberine versus placebo for the prevention of recurrence of colorectal adenoma. Lancet Gastroenterology and Hepatology, 2020. Randomised trial, 1,108 adults, up to 2 years; Chinese state research funding. PubMed 31926918.
9. Zhang Y, et al. Treatment of type 2 diabetes and dyslipidemia with the natural plant alkaloid berberine. Journal of Clinical Endocrinology and Metabolism, 2008. Randomised trial, 116 adults with type 2 diabetes, 1.0 g a day for 3 months; funding not stated on PubMed. PubMed 18397984.
10. NHS. Constipation. Page last reviewed 26 October 2023 (review was due 26 October 2026). Read 30 October 2026. nhs.uk/conditions/constipation.
11. Candrea AR, et al. The integrative role of berberine in gut microbiota modulation and cardiometabolic outcomes. Nutrients, 2026. Systematic review, 7 randomised trials; no conflicts declared. PubMed 42356246.
12. Wang S, et al. Combined berberine and probiotic treatment as an effective regimen for improving postprandial hyperlipidemia in type 2 diabetes patients. Gut Microbes, 2022. Randomised trial, 365 PREMOTE participants, 3 months; no conflicts declared. PubMed 34923903.
13. Chen C, et al. A randomized clinical trial of berberine hydrochloride in patients with diarrhea-predominant irritable bowel syndrome. Phytotherapy Research, 2015. Randomised trial, 132 adults with diarrhoea-type IBS, 8 weeks; funding not stated on PubMed. PubMed 26400188.
14. Guo H, et al. Berberine and rifaximin effects on small intestinal bacterial overgrowth (BRIEF-SIBO study). Frontiers in Pharmacology, 2023. Trial protocol, 180 patients planned; investigator-initiated. PubMed 36873985.
15. Chan E. Displacement of bilirubin from albumin by berberine. Biology of the Neonate, 1993. Laboratory and rat study. PubMed 8513024.
16. Wu X, et al. Effects of berberine on the blood concentration of cyclosporin A in renal transplanted recipients. European Journal of Clinical Pharmacology, 2005. Controlled trial, 52 against 52 transplant recipients, 3 months; funding not stated on PubMed. PubMed 16133554.
17. 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.
18. Gupte S. Use of berberine in treatment of giardiasis. American Journal of Diseases of Children, 1975. Report in children; no abstract on PubMed. PubMed 1096596.
19. Choudhry VP, Sabir M, Bhide VN. Berberine in giardiasis. Indian Pediatrics, 1972. Report in children; no abstract on PubMed. PubMed 4555485.
20. Zhang Q, et al. Comparative efficacy of diverse therapeutic regimens for small intestinal bacterial overgrowth. Therapeutic Advances in Gastroenterology, 2025. Network meta-analysis, 30 randomised trials, 1,552 adults; no conflict declared. PubMed 41394885.
21. 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.

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