Neem
Summary
Neem is an Indian tree used in Ayurveda. The only oral supplement trial randomized 80 adults with metabolic syndrome to placebo or 250–1,000 mg/day of an aqueous leaf-and-twig extract for 12 weeks; glucose, insulin resistance, HbA1c and endothelial function improved with dose. Swallowed neem oil has poisoned infants, and animal studies show antifertility effects.
Key facts
- Aqueous extract of neem leaves and twigs; neem seed oil is a different product[1]
- 80 adults with metabolic syndrome (20 per arm): 125, 250 or 500 mg twice daily for 12 weeks improved fasting and post-meal glucose, insulin resistance and HbA1c dose-dependently[1]
- Animal studies of neem leaf, seed and flower extracts found antifertility, anti-sperm and abortion-inducing effects[5]
- 1 graded human outcome on this page
- October 13, 2026
How it works
ProposedNeem leaf compounds are proposed to improve insulin signalling and reduce oxidative stress and inflammation, based on preclinical work; the trial measured glucose, inflammatory and oxidative-stress markers but not mechanism.[1]
What the human research says
Human trials only, one row per outcome. The form column shows what each trial actually tested. Grades follow our evidence-grading policy.
| Outcome | Effect | Grade | Best evidence | PMID |
|---|---|---|---|---|
| Glucose, insulin resistance and endothelial function in metabolic syndrome | Improved | Grade D | RCT · n = 80 · 2021 Adults with metabolic syndrome (India) Form: Aqueous neem leaf and twig extract · Dose: 125, 250 or 500 mg twice daily (250–1,000 mg/day) · Duration: 12 weeks Fasting and post-meal glucose, insulin resistance, HbA1c, endothelial function and most inflammation and oxidative-stress markers improved dose-dependently vs placebo. | 34582720 (opens PubMed)Source [1] |
Forms
| Form | Elemental % | Absorption (human data) | GI tolerance | Studied for |
|---|---|---|---|---|
| Aqueous neem leaf and twig extract | Varies[1] | No head-to-head human absorption data. | The trial assessed safety over 12 weeks at up to 1,000 mg/day; detailed safety results are not given in the abstract.[1] | Metabolic syndrome (one trial) |
| Neem seed oil | Varies[2][3] | Not studied as an oral supplement. | Ingestion has caused toxic encephalopathy in case reports; not a supplement form.[2][3] | Topical and pesticide use; no oral trials |
Studied doses
Doses studied in human trials ranged from 250 to 1,000 mg/day of an aqueous leaf-and-twig extract (125–500 mg twice daily) for 12 weeks.[1]
Interactions
Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.
Medicines
- Diabetes medicinesRCTNeem extract lowered fasting glucose and HbA1c in adults with metabolic syndrome, so it could add to glucose-lowering drugs; combined use is untested.[1]
Who should be careful
- Infants and children
- Neem oil given by mouth caused toxic encephalopathy in an infant, and margosa (neem) oil poisoning has caused a fatal Reye-like illness with liver and brain injury.[2][4]
- Neem oil by mouth
- Swallowing neem oil has caused toxic encephalopathy in adults as well.[3]
- People on diabetes medicines
- Glucose fell in the trial; combined use is untested.[1]
- Pregnancy, breastfeeding or trying to conceive
- Neem extracts had antifertility, anti-sperm and abortion-inducing effects in animal studies and have been investigated as a contraceptive; the supplement trial did not enrol pregnant or breastfeeding women, and no human safety data exist.[5][1]
- Other medicines
- No interaction studies exist for anticoagulants, blood-pressure drugs, antibiotics, levodopa or chemotherapy.[1]
Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.
How to read the label
Frequently asked questions
Does neem lower blood sugar?
In one 12-week trial in metabolic syndrome, a neem leaf extract lowered fasting glucose and HbA1c in a dose-dependent way.[1]
Is neem oil safe to swallow?
No. Case reports describe toxic encephalopathy after neem oil was swallowed, including in an infant.[2][3]
Is neem safe for children?
No safety data support it. Neem oil poisoning has caused toxic encephalopathy in an infant and a fatal Reye-like illness, and the supplement trial enrolled adults only.[2][4][1]
What dose of neem was studied?
125–500 mg twice daily of an aqueous leaf-and-twig extract for 12 weeks.[1]
Does neem affect fertility or pregnancy?
Possibly. In animal studies neem extracts reduced fertility and sperm production and induced abortion, and neem has been studied as a contraceptive. Human data are lacking, so use when pregnant or trying to conceive is untested.[5]
Sources
- [1]Aqueous Azadirachta indica (Neem) Extract Attenuates Insulin Resistance to Improve Glycemic Control and Endothelial Function in Subjects with Metabolic Syndrome.. J Med Food, 2021. RCT
- [2]Neem oil poisoning as a cause of toxic encephalopathy in an infant.. Indian J Pediatr, 2014. review
- [3]Neem oil poisoning: Case report of an adult with toxic encephalopathy.. Indian J Crit Care Med, 2013. review
- [4]Reye-like syndrome due to margosa oil poisoning: report of a case with postmortem findings.. Am J Gastroenterol, 1982. observational
- [5]Azadirachta indica A. Juss (neem) as a contraceptive: An evidence-based review on its pharmacological efficiency.. Phytomedicine, 2021. review
What changed
- Independent adversarial review: added margosa (neem) oil Reye-like poisoning (PMID 7081175) and the antifertility/abortifacient animal evidence (PMID 34092456) to safety, pregnancy and FAQ; summary updated.
- First draft. Every PMID checked against NCBI E-utilities esummary (title and year taken from the record) and abstracts read for the cited rows.
- Self-review pass (strict second read): leaf extract separated from neem oil. Drug interactions checked explicitly: diabetes drugs (listed); anticoagulants, blood-pressure drugs, antibiotics, levodopa, chemotherapy (no data, stated).