Why can't I eat during the physical examination

Eating is usually not allowed before physical examination, mainly to avoid interference with the accuracy of blood tests, abdominal ultrasound and other items caused by eating. The main reasons for fasting before physical examination are to avoid abnormal increase in blood sugar and blood lipids, prevent gastrointestinal contents from interfering with imaging examination, reduce the secretion of cholecystokinin that affects gallbladder imaging, reduce gastric acid secretion that interferes with gastroscopy examination, and avoid food residue affecting oral examination.

1. Avoid abnormal elevation of blood glucose and blood lipids

After eating, blood glucose and triglyceride levels may temporarily increase, especially with a high sugar and high-fat diet, which may cause false overestimation of fasting blood glucose and blood lipid test results. For example, the serum triglyceride concentration within 2 hours after eating deep-fried dough sticks at breakfast may be several times higher than the fasting state, leading to the misjudgment of hyperlipidemia. Fasting for 8-12 hours can reflect the basic metabolic state of the body, which is helpful for screening diseases such as diabetes and metabolic syndrome.

2. Prevent gastrointestinal contents from interfering with imaging examinations

Upper gastrointestinal barium meal, abdominal CT and other examinations require fasting state, and food residues in the stomach can block the display of small lesions. Undigested food during gastroscopy may mask gastric mucosal erosion or ulcers, and excessive intestinal gas can affect ultrasound observation of the pancreas and bile ducts. Some hospitals require fasting for more than 12 hours before gastroscopy to ensure clear vision.

3. Reducing the secretion of cholecystokinin affects gallbladder imaging

After eating, the gallbladder will contract and excrete bile, resulting in false impressions such as gallbladder volume reduction and wall thickening during ultrasound examination. The gallbladder is well filled on an empty stomach, which can more accurately diagnose lesions such as gallbladder polyps and stones. If it is necessary to evaluate gallbladder contraction function, doctors will specifically arrange a fat meal test instead of conducting it during routine physical examinations.

4. Reducing gastric acid secretion interferes with gastroscopy

Food stimulation will promote gastric acid secretion, increase the foam and mucus on the mucosal surface during gastroscopy, and affect the observation of gastritis, gastric ulcer and other diseases. Some hospitals may use defoamers before gastroscopy, but fasting is still a basic requirement to ensure the quality of the examination. Excessive stomach acid may also increase the risk of nausea and vomiting during the examination process.

5. Avoid food residue affecting oral examination

Oral examination requires observing the original state of teeth, gums, and mucous membranes. Food residue may mask dental caries, tartar, or oral ulcers. Especially colored foods such as coffee and tea can make dental plaque appear unclear, affecting the assessment of periodontal disease. Brushing teeth and rinsing mouth before physical examination can improve, but complete fasting can completely eliminate interference. Strict fasting is required 8-12 hours before the physical examination, but a small amount of plain water can be consumed. For those with chronic diseases who require long-term medication, a small amount of water can be used to administer the medication and inform the doctor. On the day of the inspection, avoid vigorous exercise or emotional tension, and wear loose clothing for easy inspection. After completing the fasting program, it is advisable to consume sugary foods in a timely manner to prevent hypoglycemia. Carry the physical examination form and follow the instructions for orderly examination. If fasting is not possible due to special circumstances, it is necessary to communicate with the medical examination center in advance to adjust the examination sequence.