Hello dear, Height of an individual is determined by Genetics, Environmental & Nutritional factors and Hormonal factors (most important the Growth Hormone secreted by pituitary gland in brain) An individual stops growing in height after the fusion of the Epiphyses (growth plates) of the long bones, which occurs by the age of 17-21 yrs in males. So...as you are already 21 yrs old now, there is minmal chance of any further increase in height. An X ray for bone age determination can be taken to look for the fusion of epiphyses. Make sure that you are taking a healthy & balanced diet, exercise regularly & avoid stress. Protein rich diet like soya, groundnut, pulses, etc should be incorporated in your diet plan. Consume more of natural diet like fresh fruits, green vegetables, milk, eggs, wheat, etc. Avoid oily and junk food. Stay away from smoking & alcohol. One more thing, please do not get influenced by any advertisement or health product which claim to boost your growth hormone & increase height...it may be harmful. Wishing you Good Health. Take care.