In order to determine if you are finished growing you need to have an x-ray of your hand and wrist to determine if your bones are the same age as your chronological age. This type of x-ray is a bone age. . They will also look to see if your growth plates, the part of your bones where the growth takes place are closed or open. For a boy you can calculate your predicted height from a formula. Dad height added to momma height (in inches) plus 5 inches and divide the total by 2. This will be what would be expected to be your final height within an inch or two. (Assuming you are genetically related to your parents) . Some supplements can cause anabolic effects and build muscle but are unlikely to affect your final height.