Why can’t you drink water during a physical examination? What are the consequences?

Nowadays, many employers arrange for their employees to undergo health examinations every year. Before the examination, employees will be informed of some precautions, such as not doing strenuous exercise the day before the examination, not eating midnight snacks, not eating breakfast on the day of the examination, etc. This is a fasting examination. When it comes to the definition of fasting, many people only limit their understanding to "not eating". In fact, there are also some rules for drinking water during a fasting examination.

Can I drink water before the physical examination?

It is necessary not to eat before a physical examination, but you cannot deliberately not drink water. Many people are afraid to drink water mainly because they are worried that it will affect the results of routine blood and urine tests during the physical examination. But in fact, as long as the amount of water you drink is controlled appropriately, drinking some water before the physical examination will not affect the results of the physical examination.

How much water can I drink before a physical examination?

However, according to experts, you can drink a small glass of water after getting up on the day of the physical examination to ensure the necessary water intake by the body. The blood volume of our human body accounts for about 7-8% of body weight, so a person weighing about 60 kg has a blood volume of about 4200-4800 ml.

If you drink 200 ml of water on the morning of the physical examination, and you still have some time before arriving at the physical examination center, the water you drank will have already been absorbed and penetrated into the tissues to participate in metabolism. During this half hour, 20-40 ml of urine will be produced, and some of it will be excreted through breathing and sweating. Therefore, the increase in your blood volume at that time would not exceed 40 ml, which is less than 1%, and it would not have any impact on blood indicators.

When can I drink water?

However, experts also emphasized that you cannot drink water after arriving at the physical examination center, because the physical examination includes routine blood and urine tests, and drinking water will have some impact on the results of these tests. You can drink water and eat after completing all fasting examination items.

In addition, the physical examination should first include blood drawing and B-ultrasound. If you feel thirsty or hungry, you can basically eat and drink water after completing these two items. For other items such as electrocardiogram, chest X-ray, internal medicine and surgery, ophthalmology, dentistry, and otolaryngology, it doesn't matter whether you drink water or not. Women should drink plenty of water after having their blood drawn and having B-ultrasounds of their liver, gallbladder, pancreas, spleen and kidneys to promote urine production so that they can hold their urine as quickly as possible and do gynecological B-ultrasounds to check their uterus, ovaries, etc. After the examination, go to the toilet to empty your bladder and do a gynecological examination.