Is Vitamin D3 Safe with Letrozole?
Free · No account · based on published sources including NIH ODS, FDA drug labels, and peer-reviewed literature
Ensure adequate vitamin D3 supplementation (typically 1000–2000 IU/day) as recommended by your oncologist. Have bone density (DEXA) scans performed as scheduled. Do not exceed 4000 IU/day without medical guidance.
Why this interaction occurs
Letrozole (an aromatase inhibitor) significantly suppresses estrogen production, leading to accelerated bone loss and increased fracture risk. Vitamin D3 combined with calcium is essential to mitigate aromatase inhibitor-induced bone loss and musculoskeletal symptoms.
Evidence
Evidence level: strong.
Reported safety data
The FDA’s adverse event reporting system (FAERS) has received 49,117 reports mentioning Letrozole. This reflects reported cases involving the medication in general — not confirmed causation, and not specific to the Letrozole + 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 D3 interactions → · All Letrozole interactions →
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Educational only — not medical advice.
Always confirm with your doctor or pharmacist.