Is Vitamin D Safe with Metformin?
Free · No account · based on published sources including NIH ODS, FDA drug labels, and peer-reviewed literature
Have 25-OH vitamin D levels checked at baseline and annually. Target levels of 40-60 ng/mL. Supplement with vitamin D3 (cholecalciferol) 1000-2000 IU daily with food, or as directed based on blood levels. Take alongside calcium for synergistic bone and absorption benefits.
Why this interaction occurs
Vitamin D deficiency is highly prevalent in type 2 diabetics and worsens insulin resistance. Metformin may modestly impair vitamin D absorption by reducing calcium transport, which vitamin D depends on for intestinal uptake. Conversely, adequate vitamin D levels improve insulin sensitivity and may support metformin's glucose-lowering effects. Vitamin D deficiency also compounds metformin-related calcium and B12 absorption deficits, amplifying the nutrient cascade.
Evidence
Evidence level: moderate.
Reported safety data
The FDA’s adverse event reporting system (FAERS) has received 432,898 reports mentioning Metformin. This reflects reported cases involving the medication in general — not confirmed causation, and not specific to the Metformin + supplement combination on this page.
FAERS reports are voluntary and cannot prove that a drug caused an event. Do not use report counts to assess the safety of this specific drug-supplement pair.
Frequently asked questions
Related interactions
All Vitamin D interactions → · All Metformin interactions →
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Educational only — not medical advice.
Always confirm with your doctor or pharmacist.