Herb & supplement monograph

Black Seed Drug Interactions, Uses, Effectiveness, Safety & More

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS ·Updated July 2026

What is this page for?

First and foremost: how Black Seed interacts with medications. The heart of this page is the interaction list — every drug Black Seed is known to interact with, and how serious each one is.

But these pages have grown well beyond that into a full monograph — what Black Seed is, what people use it for and how strong the evidence is, its safety and side effects, and answers to the questions we’re asked most — written and reviewed by the clinical staff at HelloPharmacist. It’s educational information from our licensed clinical databases, not medical advice, and we don’t sell or endorse products. Our editorial policy

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Black Seed Drug Interactions: The Bottom Line

From the HelloPharmacist Editorial Team · Updated July 2026

Based on the available evidence, the overall risk of a clinically significant Black Seed drug interaction appears low for most people. None of the listed interactions are rated major, and nearly all rest on animal or lab findings rather than confirmed effects in people.

Interactions deserving the most attention

The best-documented concerns involve diabetes medications and blood pressure medications, since human studies show black seed can modestly lower blood sugar and blood pressure, which could add to these drugs' effects. People taking blood thinners such as warfarin or clopidogrel should also be aware, because animal and lab research suggests black seed may slow clotting and raise bleeding risk, even though this has not been confirmed in humans. There is also a single case report linking black seed to serotonin syndrome after surgery, so those on serotonergic drugs may want extra awareness.

What the rest of the list means

Black seed appears alongside a large number of medications, but that does not mean every combination is harmful. Most of these entries are theoretical, based on possible effects on an enzyme the body uses to clear certain medications or on findings from animal and lab studies. Many of these predicted effects have never been shown to cause meaningful changes in people.

Check your medications against Black Seed

Based on HelloPharmacist’s Black Seed interaction data and reviewed under our editorial standards.

Interaction report

Drugs that interact with Black Seed

913 medications have a known interaction with Black Seed, graded by severity. Select any drug for the full evidence-based detail.

Don’t want to scroll the list? Just ask.

Tell us the medications you take and we’ll check each one against Black Seed using our pharmacist-reviewed interaction data.

AI summaries are generated from our Black Seed interaction data for education only — always confirm with your pharmacist. How we use AI

2,830 drugs

Read The List Like a Pharmacist

What Severity, Likelihood & Evidence Mean

Severity — How Serious It Can Be

Major. Clinically significant; generally best avoided, or used only under direct professional supervision.
Moderate. May need monitoring, a dose adjustment, or separating the times you take each one.
Minor. Generally not clinically significant, but still worth noting and mentioning to your pharmacist.
No known interaction. Checked against our sources with nothing documented — not the same as proven safety.

Likelihood — How Well It’s Documented

Likely. Well-controlled human studies have demonstrated the likely existence of this interaction
Probable. Interaction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
Possible. Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists
Unlikely. Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans.

Where This Data Comes From

Interaction records are evidence-graded and sourced from the Natural Medicines database (TRC Healthcare), the same reference used by pharmacists and hospitals.
Each drug listed above links to the full report for that exact Black Seed combination — clinical detail, likelihood, evidence level, and citations.
Content is reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

The big picture

The kinds of drugs Black Seed affects

Every type of medication (drug category) Black Seed is known to interact with. Open any category for the detail — or search your exact drug in the checker above.

All 14 drug categories Black Seed interacts with

Anticoagulant/antiplatelet DrugsAntidiabetes DrugsAntihypertensive DrugsClopidogrel (plavix)Cns DepressantsCyclosporine (neoral, Sandimmune)Cytochrome P450 2c9 (cyp2c9) SubstratesDiuretic DrugsImmunosuppressantsPhenytoin (dilantin)Serotonergic DrugsSildenafil (viagra)Warfarin (coumadin)Prednisolone

Anticoagulant/Antiplatelet Drugs

Theoretically, black seed may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
In vitro and animal research suggests that black seed extract can inhibit platelet aggregation and clotting, and increase bleeding time. In addition, decreased platelet counts have occurred in a human case report and in animal research.

Likelihood Possible Evidence D

Antidiabetes Drugs

Theoretically, taking black seed with antidiabetes drugs might increase the risk of hypoglycemia.
Some clinical research and numerous animal studies suggest that black seed, especially its constituent thymoquinone, can have hypoglycemic effects.

Likelihood Possible Evidence B

Antihypertensive Drugs

Theoretically, taking black seed with antihypertensive drugs might increase the risk of hypotension.
Clinical research suggests that black seed powder and oil might reduce blood pressure by 2-3 mmHg. In animal research, black seed modestly reduces blood pressure and concomitant use of black seed and amlodipine (Norvasc) or metoprolol (Lopressor) increased the blood pressure lowering effects of these drugs.

Likelihood Possible Evidence B

Clopidogrel (Plavix)

Theoretically, black seed may increase the risk of bleeding if used with clopidogrel.
Animal research shows that taking black seed extract daily for 2 weeks prior to a single dose of clopidogrel increases maximum concentrations of clopidogrel by approximately 31% and modestly decreases oral clearance. Furthermore, bleeding time was increased by 12%. This has not been shown in humans.

Likelihood Possible Evidence D

Cns Depressants

Theoretically, concomitant use with drugs that have sedative properties may cause additive effects.
Animal research suggests that black seed may have CNS depressant effects.

Likelihood Possible Evidence D

Cyclosporine (Neoral, Sandimmune)

Theoretically taking black seed might reduce the levels and clinical effects of cyclosporine.
In animal research, black seed extract decreased the maximal levels of cyclosporine in the blood by 35.5%. This has not been shown in humans.

Likelihood Possible Evidence D

Cytochrome P450 2C9 (Cyp2C9) Substrates

Theoretically, black seed might increase levels of drugs metabolized by CYP2C9.
In vitro research suggests that thymoquinone, a constituent of black seed, can decrease the metabolism of phenytoin by a mechanism possibly related to the inhibition of CYP2C9. The effect of black seed on CYP2C9 is unclear. This has not been shown in humans.

Likelihood Possible Evidence D

Diuretic Drugs

Theoretically, taking black seed with diuretic drugs might increase potassium loss and the risk of hypokalemia.
Black seed extract has shown diuretic effects in animals, which could theoretically increase potassium loss. This has not been shown in humans.

Likelihood Possible Evidence D

Immunosuppressants

Theoretically, black seed might interfere with immunosuppressive therapy.
Animal and in vitro studies suggest that black seed might stimulate immune function. However, other animal studies suggest that black seed may suppress immune function.

Likelihood Possible Evidence D

Phenytoin (Dilantin)

Theoretically, black seed might increase or decrease levels and effects of phenytoin.
In vitro research suggests that thymoquinone, a constituent of black seed, can decrease the metabolism of phenytoin. This effect may be due to inhibition of cytochrome P450 2C9 (CYP2C9). However, animal research shows that black seed decreases the maximum concentration of and total systemic exposure to phenytoin by 57% and 87%, respectively. This seems to be related to increased clearance and steady state volume of distribution. This interaction has not been shown in humans.

Likelihood Possible Evidence D

Serotonergic Drugs

Theoretically, combining serotonergic drugs with black seed might increase the risk of serotonergic side effects, including serotonin syndrome and cerebral vasoconstrictive disorders.
Animal research suggests that black seed can increase brain serotonin levels. In one case report, a 35-year-old man undergoing endoscopic surgery experienced immediate postoperative serotonin syndrome that was likely associated with the use of black seed oil 600 mg daily starting 4 days before surgery, and precipitated by the use of serotonergic pain medications, including fentanyl and oxycodone. Monitor patients for signs of serotonin syndrome and other serotonergic side effects if using black seed with serotonergic drugs.

Likelihood Possible Evidence D

Sildenafil (Viagra)

Theoretically, black seed might reduce plasma levels and the therapeutic effects of sildenafil.
Animal research shows that black seed reduces the total systemic exposure to sildenafil by 43%. So far, this interaction has not been reported in humans.

Likelihood Possible Evidence D

Warfarin (Coumadin)

Theoretically, black seed might increase levels of warfarin and increase the risk of bleeding.
In vitro research suggests that thymoquinone, a constituent of black seed, can decrease the metabolism of warfarin. This effect may be due to inhibition of cytochrome P450 2C9 (CYP2C9). The effect of black seed on warfarin metabolism is unclear. This has not been shown in humans.

Likelihood Possible Evidence D

Prednisolone

Theoretically black seed might reduce plasma levels and therapeutic effects of prednisolone.
In animal research, oral administration of a single dose of black seed oil 15 minutes prior to oral prednisolone decreases the prednisolone maximum plasma concentration by 65% and area under the curve by 25%. This has not been shown in humans.

Likelihood Possible Evidence D

Monograph

Black Seed: Uses, Safety & Side Effects

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS · Reviewed July 2026 ·

The bottom line

Black seed (Nigella sativa) is a traditional spice and remedy that has been studied for asthma, blood sugar, cholesterol, and blood pressure, with early research showing some promise but no firmly proven benefits. It is generally well tolerated in food amounts, but supplement-strength doses are less studied, so talk to your pharmacist or doctor before using it—especially if you are pregnant, breastfeeding, or take other medicines.

Scientific name: Nigella sativa
Family: Ranunculaceae
Part used: Seeds and the oil pressed from the seeds
Common forms: Whole seeds, ground powder, capsules, softgels, and cold-pressed oil

People commonly use it for

Respiratory support (asthma, allergies, cough)
Digestive upset
Immune support
Blood sugar and cholesterol support
General inflammation

Popular and traditional uses — not proof it works. See “Uses & effectiveness” below for the evidence.

Safety at a glance

OverallUse caution

Likely safe in food amounts, but higher supplement doses are less studied long-term.

PregnancyLikely Unsafe

When used orally in amounts exceeding those found in food. Black seed may decrease or inhibit uterine contractions and may have contraceptive activity...

Read the full pregnancy detail

BreastfeedingInsufficient reliable information

Insufficient reliable information available; avoid using.

Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center). Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Jump to a section

Overview

Black seed comes from the plant Nigella sativa, a small flowering plant in the buttercup family. It grows in parts of Eastern Europe, the Middle East, North Africa, and South and Western Asia. The tiny black seeds have been used as a spice and a traditional home remedy for hundreds of years.

People take black seed as whole seeds, as a ground powder, in capsules, or as a cold-pressed oil. Whole seeds also contain fiber and protein, while the oil is a more concentrated source of the plant's active compounds. It is popularly marketed for the respiratory system, digestion, and immune health.

How it works

The main active compound in black seed is thought to be thymoquinone, found in the seed oil. Black seed also contains other plant compounds, fatty acids, and antioxidants.

In laboratory and animal studies, these compounds appear to have antioxidant, anti-inflammatory, and antimicrobial effects, and may affect blood sugar, blood pressure, and the immune system. It is important to remember that effects seen in a test tube or in animals do not always carry over to people taking a supplement.

Effectiveness

Does Black Seed work?

Here’s what the research actually shows for each use — graded by Natural Medicines and reviewed by Dr. Brian Staiger, PharmD.

Evidence overview · 56 uses evaluated

9 Possibly effective 47 Insufficient evidence

How to read these evidence grades

Natural Medicines’ 7-point scale. We show each rating’s label word-for-word.

1EffectiveStrong, consistent evidence it works.

2Likely EffectiveGood evidence, though not yet conclusive.

3Possibly EffectiveSome evidence suggests a benefit.

4Possibly IneffectiveSome evidence it may not help.

5Likely IneffectiveFairly strong evidence it doesn’t help.

6IneffectiveStrong evidence it doesn’t work.

7Insufficient Reliable Evidence to RateToo little research to say either way.

Possibly Effective Acne