What vitamins are okay with femara (letrozole)?

Vitamins are OK: Femara is an enzyme-inhibitor which eliminates the conversion of testosterone to estrogen. As such, it is a valuable drug, but this elimination potentially increases the risk of bone loss. Thus taking supplemental vitamin d and getting a test to make sure your level is normal is a good idea and will not interfere with the effect of the medicine.

Not antioxidants: There are data that high doses of vitamin e supplements can interfere with cancer therapy. Vit e is an anti-oxidant. Getting it in the diet is ok, but taking it as a supplement can be harmful. Vitamin d and calcium are ok to take as high vitamin d levels are associated with decreased breast cancer recurrence.