Right to refuse medical treatment

Is it provided in our constitution anywhere that we have the "right to reject to receive medical treatment"? in other words, considering a legal adult has a fatal illness and his friends and family are providing him the required medical treatment to prolong his/her life, even though the end result is going to be death sooner or later, then, as a legal adult with a sound mind, is he/she able to exercise the wish (guaranteed legally) to stop his/her medical treatment and continue to lead his/her life till the end as per their own wishes? Kindly enlighten.