Vitamin D, of course. Depending upon the degree of inadequacy and other factors, high-dose vitamin D supplements are often prescribed by a physician. Regular supplementation and increasing your exposure to sunlight can help increase vitamin D levels that are not too low. If you are like most Americans, your vitamin D levels are subpar, meaning a well-designed daily multivitamin and mineral formula (MVM) containing 600-1000ius should be all you need such as the dotFIT MVMs. The exception is that your doctor has diagnosed a deficiency that needs greater attention.