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Moderate evidenceHeart & metabolic

Black Seed Oil (Nigella)

Nigella sativa has surprisingly consistent meta-analytic support for small reductions in blood pressure, fasting glucose and LDL-cholesterol. Effects are real but modest, and trial quality is generally low with most studies from a handful of regions.

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What the science says

  • Lowers blood pressure modestly Moderate evidence

    A meta-analysis of 11 randomized trials found Nigella sativa reduced systolic blood pressure by about 3.3 mmHg and diastolic by about 2.8 mmHg versus placebo. Short-term powdered seed preparations produced larger systolic effects than the oil, and follow-up was mostly 8-12 weeks.

  • Improves glycemic and lipid markers in prediabetes and type 2 diabetes Moderate evidence

    A meta-analysis of randomized trials in prediabetes and type 2 diabetes reported reductions in fasting blood glucose and HbA1c along with lower total cholesterol, LDL and triglycerides. Effect sizes were modest and heterogeneity was high, so this is an adjunct rather than a replacement for metformin or statins.

  • Asthma, allergy and immune claims Limited evidence

    Small trials in allergic rhinitis and asthma report symptom improvements, but samples are tiny, blinding is often inadequate, and thymoquinone content varies enormously between products. Treat these uses as unproven.

Dosage & safety

Studied doseTrials used 0.5-3 g/day of black seed oil, or 1-3 g/day of powdered seed, for 8-12 weeks. Standardized products list thymoquinone content (commonly 0.5-3%), which is the main active constituent and varies widely by brand.
SafetyCommonly causes nausea, reflux and abdominal discomfort. Contact dermatitis from topical use is well documented. Because it lowers blood pressure and glucose, it can compound the effect of antihypertensives and antidiabetic drugs — monitor for hypotension and hypoglycemia. Thymoquinone inhibits CYP enzymes and P-glycoprotein in vitro, so interactions with narrow-therapeutic-index drugs (warfarin, cyclosporine) are plausible. Avoid in pregnancy: high doses have shown uterine-relaxant and antifertility effects in animals. Products vary hugely in potency; buy from brands that publish third-party testing.

How to take it

TimingTiming does not matter; split into two doses.
With food?With meals, which reduces the reflux and nausea that are its most common complaints.
Worth knowingThymoquinone content ranges from about 0.5% to 3% between brands, so an unstandardised oil could be six times weaker than the one used in trials.

Interactions

With medications

  • antihypertensives

    Black seed lowers blood pressure, adding to your medication and risking hypotension. monitor blood pressure when you start

  • insulin, metformin and other antidiabetic medication

    Additive blood glucose lowering with a real risk of hypoglycaemia. monitor glucose closely and tell your prescriber

  • warfarin, ciclosporin and other narrow-therapeutic-index drugs

    Thymoquinone inhibits CYP enzymes and P-glycoprotein in vitro, so blood levels of these drugs could shift either way. do not combine without your prescriber monitoring levels

With other supplements

  • berberine, cinnamon and other glucose-lowering supplements

    Additive blood glucose lowering. monitor glucose if you stack them

Well-established interactions only — this is not a complete list. Always tell your doctor and pharmacist what you take.

Frequently asked questions

Does black seed oil lower blood pressure?

Moderately: a meta-analysis of 11 randomised trials found Nigella sativa lowered systolic blood pressure by about 3.3 mmHg and diastolic by about 2.8 mmHg, mostly over 8-12 weeks. Trial quality is generally low, so black seed oil is a modest adjunct, not a treatment.

Does black seed oil help with blood sugar and cholesterol?

There is moderate evidence that black seed oil modestly reduces fasting glucose, HbA1c, total cholesterol, LDL and triglycerides in prediabetes and type 2 diabetes. Effects are small and heterogeneous, so it is an adjunct rather than a replacement for metformin or statins.

How much black seed oil should I take per day?

Trials used 0.5-3 g/day of black seed oil, or 1-3 g/day of powdered seed, for 8-12 weeks, split into two doses with meals. Thymoquinone content ranges from about 0.5% to 3% between brands, so choose a standardised product.

Is black seed oil safe with medications?

Black seed oil can add to blood pressure and diabetes medication, so monitor for low blood pressure and hypoglycaemia. Thymoquinone may affect drugs such as warfarin and ciclosporin, so do not combine them without your prescriber monitoring levels, and avoid black seed oil in pregnancy.

Scientific references

Where to buy

Amazing Herbs, Premium Black Seed™, 100% Pure Cold-Pressed Black Cumin Seed Oil, 8 fl oz (240 ml)

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