Bitter melon (Momordica charantia)

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15. Safety

The cautions that matter most, stated first. (1) Anyone on insulin, a sulfonylurea or other glucose-lowering medicine who adds bitter melon may see extra glucose lowering; WHO and Braun and Cohen expect an additive effect and advise glucose monitoring, although no interaction study exists [4,7]. (2) Avoid in pregnancy [4,5,7]. (3) Do not give to children, and do not take while breastfeeding [4]. (4) Avoid in glucose-6-phosphate dehydrogenase (G6PD) deficiency, because the seeds contain vicine [5,7]. (5) A product sold in Australia as "Bittermelon Slimming Capsules" was found by the TGA to contain undeclared sibutramine [40]; bitter melon bought from unknown online sellers carries that risk.

Adverse effects in trials. No serious adverse effects were reported in the nine blinded trials; headache and gastrointestinal complaints were the most common, and 6 g pulp a day caused more diarrhoea and flatulence than placebo; liver enzymes and creatinine did not change, with wide confidence intervals [12]. Braun and Cohen describe epigastric discomfort, pain and diarrhoea that stop when treatment stops [7]. In the 12-week Mes trial, side effects were few and similar in both arms by the authors’ judgement (nausea in 4 participants on bitter gourd and 1 on cucumber; bloating or abdominal pain in 4 and 2), and liver and kidney markers did not worsen [16]. In Kim 2023, dizziness was reported by 8 of 39 participants on the extract and none of 37 on placebo (p = 0.005), and fatigue by 11 and 4 (p = 0.084). One participant on the extract developed acute hepatitis; the authors attributed it to another herbal medicine taken during the trial and excluded that participant from the analyses, and they report no critical side effects [24]. In the Yang trial one participant on the extract withdrew with a widespread papular rash, which persisted after the extract was stopped and which the investigators judged unrelated [19].

Case reports (causality by AIP, WHO-UMC wording).

• Hypoglycaemic coma and convulsions in two children aged three and four after a tea of leaves and vines taken before food [4,5]: not assessable from the summaries, and the preparation was leaf and vine, not this drug.
• Atrial fibrillation in a 22-year-old man after two days of juice of crushed bitter melon (part not stated), two tablespoons three times a day; sinus rhythm restored with amiodarone; no recurrence off the herb [41]: possible.
• Acute interstitial nephritis, biopsy-proven, in a 60-year-old woman with type 2 diabetes and hypertension after seven months of a pure extract, taken with glimepiride, metformin, gemigliptin, pioglitazone, amlodipine, losartan and carvedilol; the extract and pioglitazone were stopped and prednisolone given, and creatinine returned close to baseline in three months [42]. The authors rated the link probable (Naranjo score 6; WHO-UMC probable) [42]; AIP rates it possible, because pioglitazone was withdrawn at the same time.
• Herb-induced liver injury in a 38-year-old man taking a Haitian blend of asowosi (bitter melon), cactus and aloe vera twice daily for two to three weeks, with amoxicillin, nimesulide and two to three alcoholic drinks a week; liver histology supported herb-induced injury [43]: unassessable for bitter melon alone, given the co-exposures.
• Headache with ingestion of seeds [7].

Toxicology. Rats fed 0.02 to 0.5 per cent fruit in the diet for eight weeks showed no adverse effects; juice at 10 mL/kg for 30 days raised γ-glutamyl transferase and alkaline phosphatase [4]. Toxicity and death occurred in animals given high-dose extracts intravenously or intraperitoneally [7]. A seed extract was lethal to zebrafish embryos at 50 µg/mL, and fruit extract caused embryonic cardiac toxicity at 50 µg/mL [5]. Extracts were negative in the Ames test and positive in the comet assay [4].

Pregnancy. Avoid. Momorcharins from the seeds induced early and midterm abortion in mice and were teratogenic to cultured mouse embryos, and WHO contraindicates the seeds in pregnancy [4]. Fresh fruit juice at 6 mL/kg caused uterine bleeding in pregnant rats and rabbits, and Çiçek advises that bitter gourd preparations be avoided in pregnancy [5]. Braun and Cohen contraindicate bitter melon in pregnancy on animal evidence and traditional use (emmenagogue) [7]. Metabol Complex carries a pregnancy warning [6]. The trials read excluded pregnant women [16]. Grade: animal evidence; no human data.

Lactation. Avoid. WHO advises that the crude drug and its preparations not be taken during breastfeeding, reasoning from the severe hypoglycaemia reported in children [4]. No study of transfer into breast milk was found, and the trials read excluded breastfeeding women [16]. Grade: extrapolation from case reports; no lactation data.

Children. Do not give. WHO advises against use in children, citing hypoglycaemic coma and convulsions [4]. Grade: case reports (leaf-and-vine tea).

G6PD deficiency. Avoid, because the seeds contain vicine, which causes favism in G6PD-deficient people [5,7]. Çiçek suggests that seed-free fruit may reduce the risk [5]; certificates and labels should state whether seeds are included (section 2). Grade: mechanistic, with older human reports cited by Çiçek.

Men trying to father a child. Braun and Cohen advise against use, from antispermatogenic effects in animals [7]; seed and fruit extracts reduced spermatogenesis in rats and dogs [5]. Grade: animal.

Seeds and outer rind. Braun and Cohen advise avoiding them because of toxic lectins [7].

Warnings. WHO advises people with liver disorders to seek professional advice before use [4].

Herb-drug interactions.

WHO notes that added hypoglycaemic effects "need to be investigated" [4]. Braun and Cohen advise people with diabetes to monitor blood glucose, as medication may need changing [7]. A registered Indian trial adds bitter melon to metformin and glimepiride and lists adverse effects as an outcome (CTRI/2024/06/068929; section 13.3); no results were found. A case report of acute pancreatitis attributed to an interaction between bitter melon and the kinase inhibitor pazopanib (PubMed 34569860) has been identified; its full text is on order, it has not been read, and it is not graded here.

Older people. No specific data. The interaction and hypoglycaemia cautions apply with more force to people on several medicines, as in the nephritis case [42].

Overdose. No overdose reports were found in the sources read.

Australian regulatory signals.

• Poisons Standard: the plant is not scheduled [9].
• TGA safety alerts: a search of the TGA website for "momordica", "bitter melon", "bitter gourd" and "karela" in September 2026 returned one safety alert (a repeat search in October 2026 was stopped by the site’s automated-traffic check, so the September 2026 result stands). On 27/07/2017 the TGA warned that "Bittermelon Slimming Capsules", bought online by people in Australia, contained undeclared sibutramine, a prescription-only medicine withdrawn in 2010 after it was linked to major cardiac events; the product was not on the ARTG [40]. The risk came from the adulterant and says nothing about the fruit. The same search found a sponsor-requested cancellation of a "Bitter Melon Powder Capsule" listing on 14/03/2017, with no safety reason given [40].
• TGA Database of Adverse Event Notifications (DAEN): searched in September 2026 but not completed. The DAEN medicines search did not filter on any term entered by the non-interactive browser, including a control ingredient known to be listed, so the absence of bitter melon reports could not be confirmed. A manual DAEN search is outstanding (gap 4 in section 0.3).

Referral. Anyone with diabetes, anyone pregnant, breastfeeding or trying to conceive, anyone with G6PD deficiency, and anyone giving bitter melon to a child should consult a degree-qualified herbalist with competencies and adequate training in pharmacognosy before use.