Black seed (Nigella sativa)
Summary
Black seed (Nigella sativa) is a traditional remedy taken as ground seed or oil. Pooled trials report systolic blood pressure about 3 mm Hg lower and improvements in blood sugar and lipids, but trials are mostly small, short and highly heterogeneous. Kidney injury has been reported in a case report. Doses ranged from 200 mg to 4.6 g a day.
Key facts
- Pooled trials: systolic about 3.1 mm Hg and diastolic about 2.7 mm Hg lower, with very high heterogeneity[1]
- 82 trials (5,026 people) at 200–4,600 mg/day for 1–48 weeks reported improvements in many cardiometabolic markers[2]
- A case report described acute kidney failure linked to Nigella sativa in a person with diabetes[5]
- 2 graded human outcomes on this page
- October 11, 2026
How it works
ProposedHow black seed lowers blood pressure or blood sugar in people is not established in the sources cited here; trials measured outcomes rather than 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.
At a glance: strongest evidence per outcome
| Outcome | Grade | Effect | Strongest evidence | Rows |
|---|---|---|---|---|
| Blood pressure | Grade C | Improved | RCT · n = 70 · 2013 | 1 row |
| Blood sugar | Grade D | Improved | RCT · n = 43 · 2021 | 1 row |
Every graded row
| Outcome | Effect | Grade | Best evidence | PMID |
|---|---|---|---|---|
| Blood pressure in healthy adults | Improved | Grade C | RCT · n = 70 · 2013 Healthy adults aged 34–63 with normal blood pressure Form: Nigella sativa seed oil · Dose: 2.5 mL twice daily (5 mL/day) · Duration: 8 weeks Systolic and diastolic pressure fell versus placebo; liver and kidney blood tests did not change and no adverse effects were reported. | 23436437 (opens PubMed)Source [3] |
| Blood sugar, lipids and blood pressure in type 2 diabetes | Improved | Grade D | RCT · n = 43 · 2021 Adults with type 2 diabetes Form: Nigella sativa oil extract softgels · Dose: 1,000 mg/day · Duration: 8 weeks Fasting glucose, HbA1c, total and LDL cholesterol, triglycerides, waist and blood pressure fell versus sunflower-oil placebo; HOMA-IR and HDL did not change. | 34142392 (opens PubMed)Source [4] |
Forms
| Form | Elemental % | Absorption (human data) | GI tolerance | Studied for |
|---|---|---|---|---|
| Black seed oil (liquid or softgels) | Varies | No head-to-head human absorption data in the sources cited here. | No adverse effects and no liver or kidney test changes at 5 mL/day for 8 weeks.[3] | Blood pressure and diabetes trials |
| Ground seed (capsules) | Varies | No head-to-head human absorption data in the sources cited here. | No form-specific tolerance data in the sources cited here. | Pooled cardiometabolic trials |
Studied doses
Doses studied in human trials ranged from 200 mg to 4,600 mg of black seed per day for 1 to 48 weeks in the pooled trials; single trials used 1,000 mg of oil extract or 5 mL of oil daily for 8 weeks.[2][3][4]
Interactions
Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.
None found in our sources.
Who should be careful
- Kidney disease
- A case report linked Nigella sativa to acute kidney failure in a patient with diabetes.[5]
- People on diabetes or blood-pressure medicines
- Trials reported lower glucose and blood pressure, so effects could add to medication; the prescriber should know.[4][1]
- Pregnancy and breastfeeding
- Not studied in these groups in the trials cited here.[2]
Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.
Frequently asked questions
Does black seed oil lower blood pressure?
Pooled trials report about 3 mm Hg lower systolic pressure, with very inconsistent results between trials.[1]
Does black seed help diabetes?
Small trials report lower fasting glucose and HbA1c; one 8-week trial at 1,000 mg/day found improvements versus placebo.[4][2]
Sources
- [1]Antihypertensive effects of Nigella sativa supplementation: An updated systematic review and meta-analysis of randomized controlled trials. Phytother Res, 2023. meta-analysis
- [2]Does Nigella sativa supplementation improve cardiovascular disease risk factors? A comprehensive GRADE-assessed systematic review and dose-response meta-analysis of 82 randomized controlled trials. Pharmacol Res, 2025. meta-analysis
- [3]Blood pressure lowering effect of Nigella sativa L. seed oil in healthy volunteers: a randomized, double-blind, placebo-controlled clinical trial. Phytother Res, 2013. RCT
- [4]Effect of Nigella sativa oil extract on cardiometabolic risk factors in type 2 diabetes: A randomized, double-blind, placebo-controlled clinical trial. Phytother Res, 2021. RCT
- [5]A case study report of acute renal failure associated with Nigella sativa in a diabetic patient. J Integr Med, 2013. observational
What changed
- New monograph. Every PMID checked against NCBI E-utilities (title, journal and year from the PubMed record); each evidence row written from its abstract; intake and safety facts from the cited fact sheets.