Does black seed oil lower blood sugar, cholesterol and blood pressure?

Several meta-analyses found black seed oil modestly lowers blood sugar, LDL cholesterol and blood pressure. The evidence is early.

Published October 2026

Short answer

Trials suggest black seed oil lowers blood sugar, LDL cholesterol and blood pressure modestly. The evidence is limited and early. Evidence grade C (Limited). Several meta-analyses of mostly small, short trials; downgraded for surrogate blood-test outcomes, inconsistent results and different preparations.

Key takeaways

Meta-analyses of trials found black seed oil lowered fasting blood sugar and HbA1c, mostly in people with type 2 diabetes [1][2].
LDL cholesterol fell by about 14 to 18 mg/dL in two large reviews of trials [3][4].
Systolic blood pressure was about 3 mmHg lower in pooled trials, a modest drop [5][2].
HDL ('good') cholesterol results disagree between reviews, and the trials are mostly short [3][6][5].
Side effects in the trials were mostly mild stomach upset; no human data on drug interactions or pregnancy were found [7].

The short version

Black seed oil, made from the seeds of the Nigella sativa plant, modestly lowers blood sugar, LDL cholesterol and blood pressure in several meta-analyses of trials [1][8][3][5]. The drops are small, the trials are short, and most results come from blood tests rather than heart attacks, strokes or diabetes complications [5], so the evidence is limited.

What the studies show

Blood sugar. Three meta-analyses of 16 to 31 trials found lower fasting blood sugar and HbA1c. One review of 16 trials in people with type 2 diabetes found fasting blood sugar about 21 mg/dL lower and HbA1c about 0.44 points lower [1]. A 2026 review of 31 trials found fasting blood sugar about 19 mg/dL lower [2]. In a one-year trial of 114 people with type 2 diabetes who also took their usual medicines, fasting blood sugar fell from 195 to 172 mg/dL in the black seed group, while the placebo group stayed at 180 [9]. In a three-month open-label trial of newly diagnosed people, black seed oil capsules lowered blood sugar less than metformin, although weight fell about as much [10].

LDL ('bad') cholesterol. LDL fell by about 14 mg/dL in a review of 17 trials [3] and by about 18 mg/dL in a review of 50 trials [4]. Total cholesterol and triglycerides also fell in both reviews [3][4].

HDL ('good') cholesterol. The results disagree. One review found no change [3], a 2024 review of 34 studies found a rise [6], and a trial in type 2 diabetes found no change [11].

Blood pressure. Eleven trials with 860 people found systolic blood pressure about 3 mmHg lower than control, and diastolic about 3 mmHg lower [5]. A 2026 review of 31 trials found a similar systolic drop [2]. Single trials were mixed. In 55 adults with high blood pressure, 2.5 mL of oil twice a day for eight weeks lowered systolic pressure more than placebo [12]. In 76 older adults with high blood pressure, 300 mg of seed extract twice a day for 28 days did not beat placebo [7].

A 2025 review of 82 studies with 5,026 people, which graded its confidence in each result, reported improvements in many cardiovascular risk factors, including blood pressure, blood sugar and LDL cholesterol [13].

The nuances

The form matters. Trials used oil, ground seed powder, seed extracts, capsules and a honey mix. Oil lowered fasting blood sugar more than powder [8], while powder lowered blood pressure more than oil [5]. Results from one form do not carry over to another.

Doses varied. Doses ranged from 200 to 4,600 mg a day across the trials in the 2025 review [13]. Blood pressure trials averaged about eight weeks [5].

Results vary between trials. One 2023 blood pressure review found very high variation between its trials [14].

Side effects. In the trial of older adults, 6 of 38 people in the black seed group (15.8%) had indigestion, and some had nausea or constipation [7]. Other trials reported no serious side effects [15][16]. For fatty liver disease, liver enzymes fell more than placebo and no adverse effects were reported [17].

What this means for you

Black seed oil shows small effects on blood sugar, cholesterol and blood pressure markers, not a replacement for prescribed medicines. If you take medicines for blood sugar, blood pressure or blood clots, have liver disease, or are pregnant or breastfeeding, talk to your doctor before you start it. The full list of safety points is on the black seed oil topic page.

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Black Seed Oil — Several meta-analyses of trials suggest black seed oil modestly lowers fasting blood sugar, LDL cholesterol and systolic blood pressure.