Usually vitamin D3 is a fat-soluble vitamin and is best taken after meals from the perspective of bioavailability, and usually the best time to take it is within 15-30 minutes after meals for patients with previous gastrointestinal disorders. Especially for patients with previous upper gastrointestinal bleeding and peptic ulcers, taking it 15 minutes after a meal can fully replenish vitamin D3 and reduce the damage to the gastric mucosa and gastric mucosal irritation caused by the vitamin supplement. However, for patients with relatively good gastrointestinal function, vitamin D3 can be taken in the middle of two meals, usually after breakfast and before lunch, i.e., 9-10 a.m., for relatively good bioavailability.