Hello. I'm sorry you're having problems with your hair.
deficiency is very rare. In fact, the only two situations associated with biotin deficiency are prolonged intravenous feeding
without biotin supplementation and prolonged consumption of raw egg whites (a protein called avidin
in egg whites binds biotin and prevents its absorption from the intestine). Unless one of those situations describes you, it's unlikely your hair loss is due to biotin deficiency, and there's no good evidence that taking extra biotin will improve hair growth unless you ARE biotin deficient.
However, biotin supplements are relatively cheap, and taking extra biotin certainly won't do any harm. 1,000 to 5,000 mcg daily is a reasonable dosage range. In the meantime, I urge you to see a dermatologist
to determine the cause of your hair loss and discuss other treatment options.