Black Seed Oil (Nigella sativa)Botanical

• Blood sugar and cardiometabolic markersPossibly helps

  The largest synthesis is a 2025 GRADE-assessed dose-response meta-analysis of 82 randomized controlled trials [6].
  
  It reported significant improvements in BMI, blood pressure, and lipid profiles, along with lower inflammatory markers and better glycemic control [6].
  
  Australia's CSIRO, which researches the plant, describes trial results as mixed but mainly positive, with blood sugar in type 2 diabetes as the strongest signal [4]. ^[6]

• Reviewers read the same evidence very differentlyPossibly helps

  A framing conflict, kept visible.
  
  CSIRO and the 2025 meta-analysis describe the overall results as mainly positive [4][6].
  
  A Cleveland Clinic preventive-medicine specialist, Robert Saper, says there is no robust, rigorous evidence supporting black seed oil for any specific condition [1]. He adds that small studies raise possibilities worth researching, and that it should never stand in for conventional medicine [1]. ^[1]

• Blood pressurePossibly helps

  Individual trials and the pooled analysis disagree, so both stay on the page.
  
  MSKCC notes data on antihypertensive effects are conflicting across individual trials [9].
  
  The pooled 2025 analysis of 82 RCTs reported a significant blood-pressure-lowering effect [6]. ^[9]

• Allergic rhinitis (hay fever)Possibly helps

  A small 2014 study found topical use reduced symptoms in 92% of participants [1].
  
  Oral capsules also showed positive results in another small trial [1]. Both are small and unreplicated [1]. ^[1]

• AsthmaPossibly helps

  A small 2019 trial gave 500 mg twice daily for 4 weeks and found improved Asthma Control Test scores [1].
  
  One small trial is a starting point, not a basis for changing how asthma is managed [1]. ^[1]

• Rheumatoid arthritisPossibly helps

  A small 42-person study suggested benefit as an add-on to existing therapy [1].
  
  A separate review of thymoquinone research concluded more study is needed [5]. ^[1]

• CancerPossibly helps

  Laboratory promise, no human demonstration.
  
  A 2011 review of preclinical work called black seed oil a safe and promising anticancer agent, based on cell and animal studies [1].
  
  MSKCC states plainly that black cumin seed has not been shown to work against cancer in humans [9]. ^[9]

• Radiation dermatitis (topical)Possibly helps

  A randomized trial in breast cancer patients undergoing radiotherapy found topical Nigella sativa gel reduced the severity of acute radiation dermatitis [9].
  
  This is skin care during radiotherapy, a narrow question separate from the cancer claims above [9]. ^[9]

• Cold-pressed liquid oilThe form consumers generally prefer.

  Elemental content

  Thymoquinone is the variable that matters; analyzed oils ran 3.08 to 809.4 mg/100 g, and a separate Malaysian market analysis found 140-1,880 mg/100 g [8]

  Absorption

  No heat or solvent used; pressing below about 40C preserves thymoquinone [8]

  Best for

  The form consumers generally prefer. Lower yield and more prone to oxidation than solvent-extracted oil [8]

• Solvent-extracted oilCheaper to produce. No study compares health outcomes against cold-pressed oil in humans, so the documented difference…

  Elemental content

  Extracted with a solvent such as hexane

  Absorption

  More efficient extraction, but some beneficial compounds can be removed or degraded [8]

  Best for

  Cheaper to produce. No study compares health outcomes against cold-pressed oil in humans, so the documented difference is compositional, not clinical [8]

• Oil-filled capsules and softgelsConvenience and consistency by volume.

  Elemental content

  500-760 mg of oil per capsule in analyzed products; thymoquinone 21.46-660.5 mg/100 g [8]

  Absorption

  Same oil, pre-measured per capsule

  Best for

  Convenience and consistency by volume. Thymoquinone per capsule still varies about 30-fold across brands [8]

• Ground seed and powderCooking and everyday use. Labels almost never disclose thymoquinone content, so matching a trial dose is guesswork

  Elemental content

  Whole seed, ground — the traditional culinary form

  Absorption

  Studied at 1-2 g/day over 8-12 weeks [7]

  Best for

  Cooking and everyday use. Labels almost never disclose thymoquinone content, so matching a trial dose is guesswork [8]

• Reported side effects

  Cleveland Clinic documents rashes and allergic reactions, gastrointestinal discomfort and nausea, and irregular menstrual bleeding [1].
  
  It also cites a case report of acute kidney failure in a person with diabetes after taking black seed oil [1]. ^[1]

• Topical use

  WebMD calls black seed oil or gel possibly safe for short-term use on skin, while noting it can cause allergic rashes [15].
  
  MSKCC cites case reports of allergic contact dermatitis, and one case of DRESS syndrome — a serious systemic reaction — after repeated topical use, including in beard cosmetics [9]. ^[9]

• Surgery

  Black seed oil can slow clotting and reduce platelet counts, raising post-operative bleeding and thrombocytopenia risk [1].
  
  Cleveland Clinic, WebMD, and RxList all advise stopping it at least 2 weeks before scheduled surgery, also citing blood-sugar control and anesthesia [1][7][12]. ^[1]

• Pregnancy and breastfeeding

  RxList says black seed seems safe in food amounts during pregnancy, but calls larger medicinal amounts likely unsafe, since it can slow or stop uterine contractions [12].
  
  Breastfeeding safety is not well studied, and RxList advises avoiding it [12]. Cleveland Clinic lists pregnancy among the situations where it recommends against black seed oil entirely [1]. ^[12]

• Warfarin

  The most specific interaction documented. A 2022 pharmacokinetic modeling study found thymoquinone competitively inhibits warfarin's CYP2C9-mediated metabolism [11].
  
  It predicted meaningful effects above 18 mg thymoquinone/day, or above 1 g of Nigella sativa oil/day [11].
  
  MSKCC separately reports thymoquinone inhibited warfarin activity in vitro, with clinical significance unknown [9]. ^[11]

• Drugs cleared by CYP450 enzymes

  An in-vitro human liver microsome study found thymoquinone significantly inhibits CYP1A2, CYP2C9, and CYP3A4 [10].
  
  MSKCC's herb-drug page adds CYP2D6 and CYP3A4, and advises against combining black seed with CYP450-substrate drugs [9].
  
  Both sources note that clinical relevance in humans is not established [9][10]. ^[10]

• Anticoagulants and antiplatelets

  Black seed may slow clotting, so warfarin, clopidogrel, and similar drugs carry added bruising and bleeding risk when combined [7].
  
  Cleveland Clinic's Robert Saper advises against black seed oil for anyone on blood thinners of any type [1]. ^[7]

• Diabetes and blood pressure medications

  Black seed may lower blood sugar, adding to the hypoglycemia risk from diabetes medication [7].
  
  It may also lower blood pressure, so combining it with antihypertensives can overshoot. Watch for lightheadedness and dizziness [7]. ^[7]

• Other named drugs

  Rated moderate in WebMD's interaction data: diuretics (combined potassium-lowering effect), cyclosporine and other immunosuppressants (reduced levels or opposed effect), phenytoin (levels may rise or fall) [7].
  
  Sildenafil levels may drop, weakening its effect, and prednisolone is flagged as a minor interaction [7]. ^[7]

Unusually for a supplement, this one starts in the spice drawer [13].

Whole or ground nigella seeds go into breads — naan, Turkish flatbread, Indian paratha — as well as curries, rice dishes, and pickles [13][16].

They appear in regional blends including Bengali panch phoron and Ethiopian berbere. In Greece and Cyprus they are worked into halloumi [16].

The flavor gets described as aromatic and pungent, compared to fennel and nutmeg, and also as oniony, peppery, or smoky [13][14].

The pressed oil is used more sparingly as food, drizzled on salads or stirred into dressings, stews, and curries [16]. That is separate from taking it by the spoonful or in capsules [16].

No trial compared morning against evening dosing, so there is no evidence-backed best time [1].

What is documented cuts both ways. Cleveland Clinic lists gastrointestinal discomfort and nausea among the risks [1], while a clinical-trials review found no notable GI, liver, or kidney effects at 5 mL/day for 8 weeks in healthy volunteers [2].

Tolerability seems to track dose, individual, and product quality rather than time of day [2].

The widely repeated advice to take it with food, or on an empty stomach for absorption, could not be verified against a government, academic, or medically reviewed source. Read it as unverified [1].

One timing rule is well sourced: stop at least 2 weeks before scheduled surgery, per Cleveland Clinic, WebMD, and RxList [1][7][12].