Metformin and supplements: 3 sourced interactions
Biguanide (diabetes), also sold as Glucophage, Glumetza, Fortamet and Riomet. Of these, 3 named by an FDA label or NIH page. Plus 3 predicted from how each works (not established). Each links its source and the date it was checked.
From the Interaction Map Sources checked Oct 25, 2026
A combination missing here is not on our list; that does not mean it is safe together.
Metformin with supplements
Most serious first. Open a row for the mechanism, the source's words and the date checked.
Educational only. Check with your pharmacist or prescriber before changing anything you take.
Moderate
3AshwagandhaLabel or NIHAn NIH page names this pair (cause not established).
moderate · Named by an FDA label or NIH page · Cause not established
In the source’s own words; rated moderate from that wording, not from a study of the pair.
“There is evidence that ashwagandha might interact with some medications, including those for diabetes and high blood pressure, medicines that decrease the immune system response (immunosuppressants), sedatives, anti-seizure medications (anticonvulsants), and thyroid hormone medications.”
- NIH National Center for Complementary and Integrative Health · Ashwagandha: Usefulness and Safety, What Do We Know About Safety?
- Checked Oct 23, 2026
ChromiumLabel or NIHAn NIH page names this pair (blood sugar lowering).
moderate · Named by an FDA label or NIH page · Blood sugar lowering
In the source’s own words; rated moderate from that wording, not from a study of the pair.
“Therefore, chromium supplements might have an additive effect with metformin or other antidiabetes medications and thus might increase the risk of hypoglycemia.”
- NIH Office of Dietary Supplements · Office of Dietary Supplements · Chromium, Interactions with Medications · Metformin and other antidiabetes medications
- Checked Oct 25, 2026
GoldensealLabel or NIHAn NIH page names this pair (blood sugar lowering).
moderate · Named by an FDA label or NIH page · Blood sugar lowering
In the source’s own words; rated moderate from that wording, not from a study of the pair.
“For example, a study funded by the National Center for Complementary and Integrative Health (NCCIH) found that levels of metformin—the most commonly prescribed diabetes medicine—decreased about 25 percent in healthy adults who were given goldenseal extract plus metformin.”
“This drop was enough to potentially hinder glucose control in people with type 2 diabetes taking metformin.”
- NIH National Center for Complementary and Integrative Health · Goldenseal: Usefulness and Safety, What Do We Know About Safety?
- Checked Oct 25, 2026
Minor
3Asian ginsengPredictedBoth lower blood sugar, which may add up.
minor · Predicted from how each works, not established · Blood sugar lowering
Predicted from what each is known to do, not studied as a pair and not established.
Both lower blood sugar, which may add up.
- FDA drug label (DailyMed) · Metformin: lowers blood sugar (Metformin hydrochloride tablets (Zydus Pharmaceuticals USA), Rx, section 12.1)
- NIH National Center for Complementary and Integrative Health · Asian ginseng: lowers blood sugar (Asian Ginseng: Usefulness and Safety, What Do We Know About Safety?)
- Checked Oct 25, 2026
BerberinePredictedBoth lower blood sugar, which may add up.
minor · Predicted from how each works, not established · Blood sugar lowering
Predicted from what each is known to do, not studied as a pair and not established.
Both lower blood sugar, which may add up.
- LiverTox (NIH) · Berberine: lowers blood sugar (Berberine. LiverTox: Clinical and Research Information on Drug-Induced Liver Injury (NIDDK), Background)
- FDA drug label (DailyMed) · Metformin: lowers blood sugar (Metformin hydrochloride tablets (Zydus Pharmaceuticals USA), Rx, section 12.1)
- Checked Oct 23, 2026
Red yeast ricePredictedBoth lower blood sugar, which may add up.
minor · Predicted from how each works, not established · Blood sugar lowering
Predicted from what each is known to do, not studied as a pair and not established.
Both lower blood sugar, which may add up.
- FDA drug label (DailyMed) · Metformin: lowers blood sugar (Metformin hydrochloride tablets (Zydus Pharmaceuticals USA), Rx, section 12.1)
- NIH National Center for Complementary and Integrative Health · Red yeast rice: lowers blood sugar (Red Yeast Rice: What You Need To Know, Are red yeast rice products effective?)
- Checked Oct 25, 2026
How these lines are sourced
Three kinds of line
- Studied in people (PubMed): PubMed records that were opened and read, graded A (several controlled studies, or a finding in the dosing guidance), B (at least one controlled human study) or C (case reports, observational data or mechanism only).
- Named by an FDA label or NIH page: quoted word for word from that page. Its severity comes from the source’s wording, not from a study of the pair.
- Predicted from how each works, not established: built from sourced facts about each substance, such as the FDA’s table of enzyme roles. Never rated major.
Interaction MapCheck Metformin with everything else you take, together
Keep reading: Supplements and vitamins
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- Interaction MapCheck several medicines and supplements at once, each interaction sourced to PubMed, FDA labels or NIH; a pair we have no source for reads as not on our list, never as safe.