Drug & supplement interaction

Black Seed + Metformin, Rosiglitazone

Metformin, Rosiglitazone brand name: Avandamet.

Moderate Interaction
Medically reviewed by · Updated September 2026
The bottom line Moderate

Metformin, Rosiglitazone falls into 2 drug categories that Black Seed can interact with; the most serious is rated moderate. Theoretically, taking black seed with antidiabetes drugs might increase the risk of hypoglycemia.

Read the full interaction report
SeverityModerate
LikelihoodPossible
Interactions2
EvidenceB
What do Severity, Likelihood & Evidence mean?
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Interaction report

Black Seed and Metformin, Rosiglitazone

These two interact in 2 distinct ways. Each one is explained separately below.

Why Are There 2 Interactions?

Black Seed interacts with whole categories of medication. Metformin, Rosiglitazone falls into 2 of those categories, so it can interact with Black Seed in 2 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Moderate).

Moderate

ANTIDIABETES DRUGS

1 of 2

Why this applies to Metformin, Rosiglitazone

Metformin, Rosiglitazone falls under ANTIDIABETES DRUGS — the group Black Seed interacts with.

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.
Severity Moderate Likelihood Possible Evidence B

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.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Avandamet pairs two diabetes medicines, metformin and rosiglitazone, that both work to lower your blood sugar. Black seed (and especially its active piece, thymoquinone) appears to gently lower blood sugar too. So the concern here isn't your body clearing the drug differently. It's simply additive: two blood-sugar-lowering effects stacked together could push your numbers a little too low.

If that happens, you might feel shaky, sweaty, dizzy, lightheaded, or unusually hungry. The evidence is fairly early, coming from animal work and some lower-quality human studies, so this is a possible concern, not a guaranteed one. Food-amounts of the spice are unlikely to matter much, but concentrated supplement doses could. Don't change anything on your own. Just check in with your pharmacist or doctor first.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Meral, I., Yener, Z., Kahraman, T., and Mert, N. Effect of Nigella sativa on glucose concentration, lipid peroxidation, anti-oxidant defence system and liver damage in experimentally-induced diabetic rabbits. J Vet.Med A Physiol Pathol.Clin Med 2001;48(1
  2. Fararh, K. M., Atoji, Y., Shimizu, Y., Shiina, T., Nikami, H., and Takewaki, T. Mechanisms of the hypoglycaemic and immunopotentiating effects of Nigella sativa L. oil in streptozotocin-induced diabetic hamsters. Res Vet.Sci 2004;77(2):123-129. PubMed
  3. Kaleem, M., Kirmani, D., Asif, M., Ahmed, Q., and Bano, B. Biochemical effects of Nigella sativa L seeds in diabetic rats. Indian J Exp.Biol. 2006;44(9):745-748.
  4. Hawsawi, Z. A., Ali, B. A., and Bamosa, A. O. Effect of Nigella sativa (Black Seed) and thymoquinone on blood glucose in albino rats. Ann.Saudi Med 2001;21(3-4):242-244.
  5. Meddah, B., Ducroc, R., El Abbes, Faouzi M., Eto, B., Mahraoui, L., Benhaddou-Andaloussi, A., Martineau, L. C., Cherrah, Y., and Haddad, P. S. Nigella sativa inhibits intestinal glucose absorption and improves glucose tolerance in rats. J Ethnopharmacol. PubMed
  6. Najmi, A., Nasiruddin, M., Khan, R. A., and Haque, S. F. Effect of Nigella sativa oil on various clinical and biochemical parameters of insulin resistance syndrome. Int J Diabetes Dev.Ctries. 2008;28(1):11-14.
  7. Bamosa AO, Kaatabi H, Lebdaa FM, et al. Effect of Nigella sativa seeds on the glycemic control of patients with type 2 diabetes mellitus. Indian J Physiol Pharmacol 2010;54:344-54.
  8. Kaatabi H, Bamosa AO, Badar A, et al. Nigella sativa improves glycemic control and ameliorates oxidative stress in patients with type 2 diabetes mellitus: placebo controlled participant blinded clinical trial. PLoS One 2015;10:e0113486. PubMed
  9. Kooshki A, Tofighiyan T, Rastgoo N, Rakhshani MH, Miri M. Effect of Nigella sativa oil supplement on risk factors for cardiovascular diseases in patients with type 2 diabetes mellitus. Phytother Res. 2020.
  10. Moustafa HAM, El Wakeel LM, Halawa MR, Sabri NA, El-Bahy AZ, Singab AN. Effect of Nigella sativa oil versus metformin on glycemic control and biochemical parameters of newly diagnosed type 2 diabetes mellitus patients. Endocrine 2019;65(2):286-94. PubMed
  11. Hadi S, Daryabeygi-Khotbehsara R, Mirmiran P, et al. 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;35(7):3747-3755.
  12. Ali SM, Chen P, Sheikh S, et al. Thymoquinone with metformin decreases fasting, post prandial glucose, and HbA1c in type 2 diabetic patients. Drug Res (Stuttg) 2021;71(6):302-306. PubMed
  13. Tavakoli-Rouzbehani OM, Abbasnezhad M, Kheirouri S, Alizadeh M. Effects of Nigella sativa oil supplementation on selected metabolic parameters and anthropometric indices in patients with coronary artery disease: A randomized, double-blind, placebo-control
Moderate

CYTOCHROME P450 2C9 (CYP2C9) SUBSTRATES

2 of 2

Metformin, Rosiglitazone also falls under 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.
Severity Moderate Likelihood Possible Evidence D

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.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Avandamet combines two diabetes medicines: metformin and rosiglitazone. The part of this combo that matters here is rosiglitazone, which your liver clears partly through an enzyme called CYP2C9. In test-tube studies, a compound in black seed (thymoquinone) seemed to slow that enzyme down. If that happened in real life, rosiglitazone could build up a bit, which might mean stronger blood-sugar lowering and a higher chance of side effects like low blood sugar, swelling, or weight gain. Metformin is handled differently and isn't really affected by this.

Here's the honest part: this is only a theoretical concern from lab work, never shown in actual people. Food amounts of black seed are very unlikely to matter. Still, if you're considering supplement-strength black seed, check with your pharmacist or doctor first and keep an eye on your blood sugars.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Wang Z, Wang X, Wang Z, et al. Potential herb-drug interaction risk of thymoquinone and phenytoin. Chem Biol Interact. 2022;353:109801. PubMed

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction 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.
  • PossibleInteraction 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.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Black Seed Also Interacts With Other Medications

Black Seed has 911 moderate known drug interactions in our database — the Metformin, Rosiglitazone one above is among them. If you take anything else, check it against the full list below.

Moderate 911 No known interaction 1,919 (incl. Metformin, Rosiglitazone)
Taking anything else?

Check Another of Your Medications Against Black Seed

Covers the 2,830 medications we’ve checked against Black Seed. Pick one to open its full report.

From our Q&A

Questions About Black Seed or Metformin, Rosiglitazone

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Black Seed or Metformin, Rosiglitazone, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Metformin, Rosiglitazone

This page covers Black Seed only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Metformin, Rosiglitazone page lists 315 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Beer (major), Siberian Cocklebur (major), Wine (major) and Acai (moderate).

By severity: 4 major · 268 moderate · 43 minor.

From our pharmacist’s overview on the Metformin, Rosiglitazone page

“Avandamet pairs metformin with rosiglitazone to manage type 2 diabetes, and its supplement list calls for genuine care rather than a quick skim. Start with the four major-rated entries: alcohol and the herb Siberian cocklebur can each stress the liver, a serious concern with rosiglitazone on board, while activated charcoal can soak up…”

Reviewed by 2 · Jul 18, 2026

Open the Metformin, Rosiglitazone interaction page

One more smart check

Taking Black Seed as Part of a Dietary Supplement Product? Check It for Interactions

We hold 226 real supplement products containing Black Seed, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Black Seed. Your product may carry other ingredients that interact with Metformin, Rosiglitazone too, on top of Black Seed — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Black Seed and Metformin, Rosiglitazone Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Black Seed
Top 25%

#187 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Metformin, Rosiglitazone
Steady interest

#1,709 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Supplement

About Black Seed

What is Black Seed?

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

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.

Read the full Black Seed monograph & all interactions
Keep checking

Other Drugs & Black Seed

Browse every other medication we’ve checked against Black Seed — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
911Moderate
0Minor
1,918No known interaction
911 Moderate 1,918 No interaction
Moderate

911 interactions

Showing 60 of 911 moderate interactions — see all 911 on the Black Seed page.

No interaction 1,918 drugs checked — show the list

We also checked Black Seed against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 1,918 medications checked with no known interaction — see the full Black Seed list.

See the full Black Seed interactions page
See every supplement checked against Metformin, Rosiglitazone, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

Keep exploring
Black Seed monograph › Uses, safety, and every drug interaction in one place Metformin, Rosiglitazone supplement interactions › Every supplement checked against Metformin, Rosiglitazone, ranked by severity Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Black Seed and Metformin, Rosiglitazone Together: Common Questions

Can you take Black Seed with Metformin, Rosiglitazone?
There is a moderate interaction, so it may be acceptable with monitoring or timing changes — but check with your pharmacist first. Read the full details on this page and confirm with your pharmacist before combining them.
Why are there 2 interactions listed for Black Seed and Metformin, Rosiglitazone?
Metformin, Rosiglitazone belongs to more than one drug category, and Black Seed interacts with each of those categories a little differently. We list every one so nothing is missed — your overall risk is driven by the most serious of them.
How serious is the Black Seed and Metformin, Rosiglitazone interaction?
We rate it Moderate. This combination may require monitoring, a dose adjustment, or separating the times you take each one. Consult your pharmacist before using them together.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Still Have a Question About Metformin, Rosiglitazone and Black Seed?

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.