What the evidence says. Graded moderate: many meta-analyses of dozens of RCTs consistently find real but small reductions in fasting glucose, HbA1c, LDL and blood pressure, yet most trials are short (8–12 weeks), small, of modest quality and concentrated in a few regions, so it is a useful adjunct rather than a primary therapy. (Moderate evidence: Several controlled trials; effects real but modest or context-dependent.)
What is Black Seed Oil?
Black Seed Oil (Nigella sativa) is a gut and immune supplement used for lower blood sugar & hba1c. NutriDex grades the human evidence as Moderate. Black seed oil is pressed from Nigella sativa seeds; its main active is thymoquinone. Unusually for a botanical, it has a large RCT base. Pooled analyses in people with prediabetes or type 2 diabetes show meaningful drops in fasting glucose (around 24 mg/dL) and HbA1c (about 0.5–0.7%), plus lower total and LDL cholesterol. Blood-pressure meta-analyses report small reductions (roughly 3 mmHg systolic, 2.8 mmHg diastolic), and weight/obesity reviews show modest loss of about 1.5 kg and 0.6–0.9 kg/m² BMI, but little change in waist circumference. Effects on inflammatory markers like CRP are inconsistent. The catch: most trials run only 8–12 weeks, enrol few people, vary in oil quality and dose, and cluster in the Middle East and South Asia, so long-term and generalisable benefit is unproven. Best viewed as an adjunct to standard diet, exercise and medication.
Purported Benefits
✓Lower blood sugar & HbA1c
✓Improve cholesterol & LDL
✓Modestly lower blood pressure
✓Small reductions in weight & BMI
Evidence by outcome
The same supplement can be well-proven for one use and unproven for another — here is the human evidence graded outcome by outcome.
Outcome
Evidence
Effect
Studies
Lower fasting glucose & HbA1cMultiple meta-analyses in pre/T2DM show FBG ~-24 mg/dL and HbA1c ~0.5-0.7%, but trials are short (8-12 wk) and regionally clustered.
Moderate
↑ benefit · moderate
4
Improve total & LDL cholesterolPooled RCTs show significant LDL/total-cholesterol reductions (LDL ~-20 mg/dL), though oil quality and dosing vary.
Moderate
↑ benefit · moderate
3
Lower blood pressureMeta-analysis of 11 RCTs: SBP -3.3 mmHg, DBP -2.8 mmHg over ~8 weeks; small clinically modest effect.
Moderate
↑ benefit · small
2
Reduce body weight & BMIGRADE meta-analyses show weight ~-1.5 kg and BMI ~-0.6 to -0.85; no change in waist circumference.
Generally well tolerated at doses up to ~3 g/day for up to 3 months; the commonest effects are mild GI upset, nausea and occasional allergic skin reactions, with rare reports of raised liver enzymes. Because it lowers glucose and blood pressure, it can add to the effect of antidiabetic and antihypertensive drugs (watch for hypoglycaemia or dizziness). Thymoquinone inhibits CYP2C9/2D6/3A4 and may slow clotting, so it can raise levels or bleeding risk with warfarin and other anticoagulants/antiplatelets and with drugs cleared by those enzymes; it may also affect thyroid medication. Stop before surgery and avoid in pregnancy. Educational only — always check with your doctor or pharmacist before combining Black Seed Oil with any medicine.
Black Seed Oil is most often taken for Lower blood sugar & HbA1c, Improve cholesterol & LDL, Modestly lower blood pressure, Small reductions in weight & BMI. Thymoquinone-rich seed oil with modest cardiometabolic effects.
Does Black Seed Oil work — what does the evidence say?
Moderate evidence. Several controlled trials; effects real but modest or context-dependent. Black seed oil is pressed from Nigella sativa seeds; its main active is thymoquinone. Unusually for a botanical, it has a large RCT base. Pooled analyses in people with prediabetes or type 2 diabetes show meaningful drops in fasting glucose (around 24 mg/dL) and HbA1c (about 0.5–0.7%), plus lower total and LDL cholesterol. Blood-pressure meta-analyses report small reductions (roughly 3 mmHg systolic, 2.8 mmHg diastolic), and weight/obesity reviews show modest loss of about 1.5 kg and 0.6–0.9 kg/m² BMI, but little change in waist circumference. Effects on inflammatory markers like CRP are inconsistent. The catch: most trials run only 8–12 weeks, enrol few people, vary in oil quality and dose, and cluster in the Middle East and South Asia, so long-term and generalisable benefit is unproven. Best viewed as an adjunct to standard diet, exercise and medication.
What is the typical dose of Black Seed Oil?
Commonly 1–3 g/day of seed powder or 0.5–3 mL/day of cold-pressed oil, for 8–12 weeks; oil tends to outperform powder for blood pressure.
Is Black Seed Oil safe? Any cautions or side effects?
Generally well tolerated at doses up to ~3 g/day for up to 3 months; the commonest effects are mild GI upset, nausea and occasional allergic skin reactions, with rare reports of raised liver enzymes. Because it lowers glucose and blood pressure, it can add to the effect of antidiabetic and antihypertensive drugs (watch for hypoglycaemia or dizziness). Thymoquinone inhibits CYP2C9/2D6/3A4 and may slow clotting, so it can raise levels or bleeding risk with warfarin and other anticoagulants/antiplatelets and with drugs cleared by those enzymes; it may also affect thyroid medication. Stop before surgery and avoid in pregnancy.
How many studies support Black Seed Oil?
NutriDex cites 13 sources for Black Seed Oil, graded "Moderate".
Cite this page
APA
Peh, D. (2026). Black Seed Oil (Nigella sativa): Benefits, Dosage, Side Effects & Evidence. NutriDex — The Supplement Research Compendium. Retrieved 16 Sept 2026, from https://nutridex.info/s/black-seed-oil
BibTeX
@misc{nutridex_black_seed_oil,
author = {Peh, Daryl},
title = {Black Seed Oil (Nigella sativa): Benefits, Dosage, Side Effects \& Evidence},
year = {2026},
howpublished = {NutriDex --- The Supplement Research Compendium},
url = {https://nutridex.info/s/black-seed-oil},
note = {Reviewed by Dr Daryl Peh, MBBS Singapore, MMed FM. Accessed 2026-09-16}
}
For medical claims, citing the underlying primary studies linked above is preferred. NutriDex is an educational reference, not medical advice.