Medical Ninjutsu is a Sub-jutsu, which, as its name implies, has healing capabilities. It will turn your chakra into HP when used. You will drain more chakra than you gain HP. A similiar jutsu is the Slug Summoning, as they both provide HP for chakra. However, with the Slug Summoning, you can still recharge your chakra, but with the Medical Ninjutsu, you cannot.