How can i increase height after the age of 20????

You cannot: As a 20 year old male, your growth is likely done and your bones growth plates closed. There are no supplements or hormones you could take that are going to make a difference at this point in time. You need to accept where you are at and get on with living your life at your current stature.

Platform shoes: The growth centers of most males will close by age 18 although a few will grow a little longer.By 20, the growth centers have closed and you are done. If you wish,an x-ray of your hand could identify any additional growth potential.Good diet,exercise and proper rest allows you to reach your maximum height.

Growing Pains: You cannot increase your height. This is set and you are most likely done growing.

Very unusual: Virtually everyone has fused all of their growth plates by the time they are 20 years old. Once your growth plates are fused, growth is over. Even the very rare person who still has growth potential left at 20, has very limited growth potential before complete fusion, and nothing substantially affects the ultimate height.

Platform shoes: At age 20, there is no way to "grow" taller.The growth centers that determine linear growth close after adolescence, at 16-17 in most females and 18 in most males.After closure, you can not grow taller.

Shoe selection: The growth centers of most males will close by age 18 although a few will grow a little longer.By 20, the growth centers have closed and you are done. If you wish, an x-ray of your hand could identify any additional growth potential.Good diet, exercise and proper rest allows you to reach your maximum height.