Quick answer

Ask your pharmacist or doctor before combining. NIH says chromium might add to the blood sugar lowering effect of metformin and other diabetes medicines, raising the risk of hypoglycemia, or low blood sugar. This rests on studies of chromium alone. Most multivitamins contain 35 to 120 mcg of chromium, so they count too.^1,2

Key facts

NIH lists metformin and other antidiabetes medications among the medicines chromium supplements might interact with.^1,2
NIH names insulin separately: chromium might increase insulin sensitivity, so the two together could cause low blood sugar.²
MedlinePlus tells people on metformin to tell their doctor and pharmacist about every vitamin and supplement they take.³
The metformin label says low blood sugar can happen more often when metformin is taken with certain other diabetes medicines. It does not mention chromium; the chromium caution comes from NIH.⁴

Ask your pharmacist or doctor first

Some studies suggest chromium might lower blood glucose. NIH says it might therefore add to the effect of metformin and other diabetes medicines and raise the risk of low blood sugar (hypoglycemia).^1,2

Expected from how the two work, not shown in studies

What is documented

NIH's fact sheet for health professionals says some studies indicate that chromium supplementation might lower blood glucose. It concludes that chromium might therefore have an additive effect with metformin or other antidiabetes medications and increase the risk of hypoglycemia. The consumer fact sheet gives the same warning in plainer words.^1,2

This is an expected interaction. NIH reasons from studies suggesting chromium might lower blood glucose, and it does not describe a measured interaction between the two. That makes it a caution to discuss, not a measured effect.²

Insulin and other diabetes medicines

Ask your pharmacist or doctor first

Chromium might increase the body's sensitivity to insulin, so taking it with insulin could raise the risk of low blood sugar (hypoglycemia), according to NIH.^1,2

Expected from how the two work, not shown in studies

The consumer sheet words the metformin caution as covering metformin and other antidiabetes medications, so it is not limited to one drug. If you take more than one medicine for diabetes, raise each of them with your pharmacist.¹

Knowing the signs of a low

MedlinePlus advises everyone on metformin to know the symptoms of low and high blood sugar and what to do about them. If you start, stop or change a chromium supplement, ask whether you should check your blood sugar more often for a while.³

Do not stop or change your diabetes medicine to try a supplement. NCCIH says it is very important not to replace medical treatment for diabetes with an unproven product or practice.⁵

What to ask your pharmacist

Could chromium change my blood sugar readings or the dose I need?
Does my multivitamin contain chromium, and how much?
Should I check my blood sugar more often if I start or stop chromium?
Is there any reason for me to take chromium at all?

Write down every supplement you use, with the amount from its label, before the conversation. Chromium turns up in multivitamins, not only in products sold as chromium.²

Questions people ask

Does the chromium in a multivitamin count?

Yes. Most multivitamins contain 35 to 120 mcg of chromium, so mention your multivitamin when you ask about chromium and metformin.²

Can chromium replace metformin?

No. NIH notes that the American Diabetes Association does not recommend chromium supplements for people with diabetes, because they do not have a clear benefit, and NCCIH warns against replacing medical treatment with unproven products.^1,5

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Sources

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.