Endocrine therapy for breast cancer can be supplemented by calcium supplements, such as calcium gluconate, calcium carbonate, calcium lactate, etc. There is no absolute good or bad. Breast cancer treatment is related to a variety of factors such as physical condition, tumor stage, pathology type and so on. Among them, endocrine therapy is suitable for hormone receptor (ER or PR) positive breast cancer. It stops the growth of cancer cells by blocking hormones, mainly including tamoxifen, letrozole and exemestane. Calcium can be supplemented during endocrine therapy for breast cancer through calcium gluconate, calcium carbonate, and calcium lactate. In addition, dietary supplements can also be taken, choosing to eat foods with high calcium content, such as milk, tofu, soy milk, cabbage, greens, spinach and so on. And pay attention to more sunshine to promote calcium absorption. Breast cancer patients should undergo regular checkups in hospitals and carry out appropriate treatment and rehabilitation exercises under the guidance of doctors.