If you take calcium tablets for osteoporosis, at least two types of drugs are needed: 1. vitamin D. The elderly have low levels of vitamin D and cannot synthesize enough active vitamin D. Therefore, after eating calcium tablets, they are only in the digestive tract and cannot be absorbed into the blood, so you must take calcium tablets with vitamin D to absorb calcium from the intestines into the blood. 2. anti-bone resorption drugs, after taking calcium tablets, calcium will only be on the bones when it enters the blood, but if you do not take antiresorption drugs, the calcium on the bones will be lost. If you don’t take anti-resorption drugs, the calcium on the bones will be thrown down, just like a bear breaking a stick, eating one and losing the other, and it will not achieve the purpose of treating osteoporosis. Therefore, if you take calcium tablets to treat osteoporosis, you must also take anti-resorptive drugs to treat it. Anti-bone resorption drugs include estrogen, estrogen receptor modulators, or bisphosphonate drugs, all of which have an anti-bone resorption effect.