The reasons for constipation after taking calcium supplements are mainly the reaction between calcium carbonate and gastric acid and the effect of hypercalcemia. The main reason for constipation after taking calcium supplements is that after taking the medication, the calcium and food residues are not well absorbed by the intestines and form insoluble substances, which leads to constipation; it may be due to the reaction between calcium carbonate and stomach acid, which affects the normal peristaltic movement of the intestines and stomach, which leads to constipation; or it may be due to the hypercalcemia that slows down the peristaltic movement of the intestines and stomach, which leads to constipation. Calcium supplements mainly include calcium tablets and vitamin D. Calcium supplements are good for the development of bones, making the body straight, and for maintaining the body’s toughness, making the body less susceptible to injuries. However, overdose of calcium supplements may cause urinary tract stones, hypercalcemia, alkalosis and other hazards. Therefore, calcium supplements should be taken in moderation and not in excess under the professional guidance of a doctor.