Is Vitamin D3 Safe with Tamoxifen?
Free · No account · based on published sources including NIH ODS, FDA drug labels, and peer-reviewed literature
Have your vitamin D levels checked regularly during tamoxifen therapy. Supplementation to maintain serum 25-OH-D levels of 40–60 ng/mL is generally recommended under oncologist supervision to protect bone density.
Why this interaction occurs
Tamoxifen's estrogenic antagonism can negatively impact bone mineral density in premenopausal women. Vitamin D3 supports calcium absorption and bone health, and emerging evidence suggests vitamin D may have synergistic anticancer effects with tamoxifen in breast cancer.
Evidence
Evidence level: moderate.
Reported safety data
The FDA’s adverse event reporting system (FAERS) has received 22,724 reports mentioning Tamoxifen. This reflects reported cases involving the medication in general — not confirmed causation, and not specific to the Tamoxifen + 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 Tamoxifen interactions →
Already checked this one — check your whole list
Educational only — not medical advice.
Always confirm with your doctor or pharmacist.