Does drinking water affect fasting blood sugar?

The effect of drinking water on fasting blood glucose mainly depends on the following situations.

1. Drinking a small amount of water: Water consists mainly of hydrogen and oxygen and contains no sugar or calories. Therefore, drinking water alone does not cause an increase in blood glucose. In practice, patients are usually allowed to drink a small amount of water before measuring fasting blood glucose to relieve thirst or take medications.

2. Drinking a large amount of water: Consuming a large volume of water within a short period may dilute the blood, thereby lowering the concentration of glucose in the blood, which could lead to a falsely low fasting blood glucose reading. Therefore, excessive water intake within a short time should be avoided prior to a fasting blood glucose test.

3. Other situations: If sugar or other sweetened substances are added to the water, drinking such water may affect blood glucose levels. Additionally, in certain situations, such as drinking a large amount of water following severe dehydration, the blood may be temporarily diluted, causing the blood glucose concentration to appear lower. However, this does not indicate a true decrease in blood glucose levels, but rather an increased proportion of water in the blood.