You need to choose calcium tablets produced by regular manufacturers and purchased through regular channels with the right dosage. 1. Regular manufacturers: If it is a health product, it will have a “blue hat” logo, and at the same time have a health product approval number. If it is a drug, it will have a drug approval number, and over-the-counter drugs have an OTC logo. Health food and drug approval number can be in the State Food and Drug Administration’s official website for query. 2. Regular channels: Go to regular pharmacies or hospitals to avoid buying counterfeit products. 3. Appropriate dosage: some calcium tablets contain relatively small amounts of calcium, which cannot meet the body’s supplementation needs. For example, healthy adults need 800mg of calcium a day. However, some calcium tablets only contain 100mg of calcium in one tablet, which is equivalent to the calcium content of 100ml of milk, and this kind of calcium tablets is obviously insufficient in calcium content. Calcium tablets need to be used under the guidance of a doctor to ensure safety and effectiveness.