Is it healthy to take vitamins that aren't prescribed by doctors. ?

Vitamins: Yes as long as you are careful to get good advice from other professionals. Do your own research--e.g. Google it.

Googling???: I am hesitant about "googling" for medical information because internet info is often not revoewed or verified by educated experts. Any one can post anything whether safe or true statements. Check with your doctor or make sure it is a validated site such as healthtap.