Important information is missing here, you age, gender, and race. (I am not asking you to provide this information, I'm suggesting people see medical advise before arbitrarily starting a supplement)

Your skin's pigment density is an important aspect of how you handle sunlight. Your ability to process these chemicals is a function of all three, lifestyle, and other health factors.

http://www.medscape.com/viewarticle/715417 http://en.wikipedia.org/wiki/Vitamin_D