Drug & supplement interaction

Safflower + Metformin Hydrochloride

Metformin Hydrochloride brand name: Riomet ER.

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

Safflower has a moderate interaction with Metformin Hydrochloride. Theoretically, safflower oil might alter the effects of antidiabetes drugs.

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

Safflower and Metformin Hydrochloride

Here is the interaction we found between these two, with the evidence behind it.

Moderate

ANTIDIABETES DRUGS

Why this applies to Metformin Hydrochloride

Metformin Hydrochloride falls under ANTIDIABETES DRUGS — the group Safflower interacts with.

Theoretically, safflower oil might alter the effects of antidiabetes drugs.
Some clinical research shows that taking safflower oil 10 grams daily for 3 weeks can increase fasting blood glucose in patients with type 2 diabetes. However, clinical research in patients with metabolic syndrome with or without impaired glucose tolerance shows that taking safflower oil 8 grams daily for 12 weeks reduces fasting glucose levels by around 8 mg/dL. Some clinical research also shows that taking safflower oil 8 grams daily for 16 weeks does not affect fasting glucose levels in patients with type 2 diabetes.
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

Here's the honest picture with safflower oil and your metformin. Metformin lowers blood sugar mainly by helping your body use insulin and by cutting down sugar made by the liver, and it isn't a prodrug, so this isn't about one substance speeding up or blocking the other in your liver. The concern is simpler: safflower oil itself may nudge your blood sugar around a little, which could add to or work against what metformin is doing.

The studies actually point in different directions. One small trial saw fasting sugar go up a bit, another saw it drop slightly, and another saw no change at all. That's weak, mixed evidence, so I wouldn't panic. If you start a concentrated safflower or CLA supplement, just check your readings more closely and watch for unexpected lows or highs. Talk with your pharmacist or doctor before adding it. Cooking with the oil is unlikely to matter.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Borkman M, Chisholm DJ, Furler SM, et al. Effects of fish oil supplementation on glucose and lipid metabolism in NIDDM. Diabetes 1989;38:1314-9.. PubMed
  2. Asp ML, Collene AL, Norris LE, Cole RM, Stout MB, Tang SY, Hsu JC, Belury MA. Time-dependent effects of safflower oil to improve glycemia, inflammation and blood lipids in obese, post-menopausal women with type 2 diabetes: a randomized, double-masked, cro
  3. Ruyvaran M, Zamani A, Mohamadian A, et al. Safflower (Carthamus tinctorius L.) oil could improve abdominal obesity, blood pressure, and insulin resistance in patients with metabolic syndrome: a randomized, double-blind, placebo-controlled clinical trial. 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

Safflower Also Interacts With Other Medications

Safflower has 207 moderate known drug interactions in our database — the Metformin Hydrochloride one above is one of them. If you take anything else, check it against the full list below.

Moderate 207 No known interaction 2,623 (incl. Metformin Hydrochloride)
Taking anything else?

Check Another of Your Medications Against Safflower

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

Everything else you take

See Every Supplement That Interacts With Metformin Hydrochloride

This page covers Safflower only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Metformin Hydrochloride page lists 257 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Siberian Cocklebur (major), Acai (moderate), African Wild Potato (moderate) and Agaricus Mushroom (moderate).

By severity: 2 major · 217 moderate · 38 minor.

From our pharmacist’s overview on the Metformin Hydrochloride page

“Anyone taking metformin hydrochloride (Riomet ER) should treat this list with genuine care, because two of its 257 entries are rated major. Siberian cocklebur has caused severe hypoglycemia in people and should not be combined with metformin at all, and activated charcoal can adsorb the drug in the gut so less reaches your blood.”

Reviewed by 2 · Jul 18, 2026

Open the Metformin Hydrochloride interaction page

One more smart check

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

We hold 276 real supplement products containing Safflower, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Safflower. Your product may carry other ingredients that interact with Metformin Hydrochloride too, on top of Safflower — 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 Safflower and Metformin Hydrochloride 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 Safflower
Top half

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

29 days ago today
Medication Metformin Hydrochloride
Top 10%

#152 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 Safflower

What is Safflower?

Safflower
  • Heart and cholesterol support
  • Skin moisturizing
  • Menstrual cramps
  • Mild constipation
  • Weight management (oil)

Safflower is a thistle-like plant used mainly for its seed oil (a common cooking oil) and its colorful flowers. Safflower oil is a reasonable source of unsaturated fats, but strong proof that supplements treat specific diseases is limited. The flower extracts have much weaker evidence and should be used with caution, especially during pregnancy.

Read the full Safflower monograph & all interactions
Keep checking

Other Drugs & Safflower

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

0Major
207Moderate
0Minor
2,622No known interaction
207 Moderate 2,622 No interaction
Moderate

207 interactions

Showing 60 of 207 moderate interactions — see all 207 on the Safflower page.

No interaction 2,622 drugs checked — show the list

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

Showing the 60 most looked-up of 2,622 medications checked with no known interaction — see the full Safflower list.

See the full Safflower interactions page
See every supplement checked against Metformin Hydrochloride, 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
Safflower monograph › Uses, safety, and every drug interaction in one place Metformin Hydrochloride supplement interactions › Every supplement checked against Metformin Hydrochloride, 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 Safflower and Metformin Hydrochloride Together: Common Questions

Can you take Safflower with Metformin Hydrochloride?
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.
How serious is the Safflower and Metformin Hydrochloride 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 Hydrochloride and Safflower?

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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.