Vitamin D supplementation is usually taken between meals, for example, after breakfast and before lunch, i.e. between 10 and 11 am, and after lunch and before dinner, i.e. between 17 and 18 pm. This is the best time to take vitamin D because it has the greatest bioavailability and is taken on an empty stomach, but the abdominal cavity is not completely emptied, so it does not burn or scorch the gastric mucosa. However, for some patients, such as those who have had chronic gastritis, duodenal ulcers, or gastric ulcers, it is not suitable to take it during the above time period. For patients with chronic stomach problems, it is recommended to take it 15-30 minutes after a meal.