First, avoid the influence of diet and other factors on some components in the blood. Because food is absorbed into the blood by the gastrointestinal tract and then transported to the whole body by the blood, the concentration of some components in the blood will increase, thus affecting the accuracy of the test results.

Second, after eating, all kinds of digested food chyle particles are quickly absorbed into the blood, making the blood appear turbid, usually called "fatty blood", which makes it impossible for inspectors to observe clearly.

Third, the mood is relatively stable in the morning, and the body is in a state of basal metabolism. The results can truly reflect the actual situation.

Fasting means not eating after dinner and not eating breakfast the next morning. In this case, a blood test is the best.