How many hours should one fast for a physical examination?
Nov 22, 2022
Source: Cainiu Health
Dr. Yang Shuwen
Introduction
A physical examination generally requires fasting for approximately eight to twelve hours to avoid affecting the test results. After food enters the digestive tract, including the stomach and small intestine, it is broken down by digestive fluids into various small molecules. These molecules are absorbed by the body and enter the bloodstream, potentially influencing the outcomes of laboratory tests and thereby affecting the accuracy of the examination.
Generally, it is necessary to fast for about eight to twelve hours before a physical examination to avoid affecting the test results.
During a physical exam, tests such as blood glucose and lipid levels are commonly performed. If food is consumed within eight hours prior to the exam, it enters the digestive tract—including the stomach and small intestine—and is broken down by digestive enzymes into various small molecules. Once absorbed into the bloodstream, these molecules can interfere with laboratory test results, thereby compromising the accuracy of the examination.
For example, foods high in sugar, after being digested and absorbed in the gastrointestinal tract, may lead to elevated blood glucose levels. Foods high in fat can increase blood lipid levels. Consuming alcohol places extra metabolic burden on the liver and kidneys, potentially affecting assessments of liver and kidney function. Beverages such as coffee and tea can stimulate the central nervous system, increasing excitability and also influencing examination outcomes.
Therefore, it's important to maintain a light diet the day before a physical exam. Avoid eating for eight to twelve hours prior to the exam to ensure accurate results.
