Is Vitamin D Safe with phenytoin?
Free · No account · based on published sources including NIH ODS, FDA drug labels, and peer-reviewed literature
Discuss Vitamin D supplementation with your doctor if you are taking phenytoin, as phenytoin may reduce Vitamin D effectiveness and levels.
Why this interaction occurs
Phenytoin is listed as impairing the efficacy of Vitamin D, likely through enzyme induction increasing Vitamin D metabolism, which may affect bone health over time.
Evidence
Evidence level: strong.
Data source
FDA Drug Label
Reported safety data
The FDA’s adverse event reporting system (FAERS) has received 25,235 reports mentioning phenytoin. This reflects reported cases involving the medication in general — not confirmed causation, and not specific to the phenytoin + 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 phenytoin interactions →
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Educational only — not medical advice.
Always confirm with your doctor or pharmacist.