Whether you can grow taller by taking calcium tablets at the age of 21 depends on whether the epiphysis has closed. If it has disappeared, it is impossible to grow taller, and the epiphysis has closed. If the epiphyseal cartilage still exists, you can take oral calcium tablets to replenish calcium ions, which can help you grow taller. It is also necessary to supplement meat, milk, eggs and other foods with a high protein content, and to do more outdoor sports and sunshine to improve the body’s vitamin D, which helps the absorption of calcium ions. When doing outdoor exercises, you should do more vertical jumps, which can stimulate the growth of bones. It is also important to keep the extremities warm, as blood circulation is richer and can provide more arterial blood. Arterial blood contains higher energy nutrients as well as electrolyte content, which helps to promote rapid growth of epiphyseal cartilage growth areas. If you get cold, it will cause the blood circulation to slow down, which will also have an effect on the growth of height.