Can I eat before the physical examination?

Physical examinations are usually scheduled in the morning, and many examination items require fasting. The strict fasting physical examination not only means that you cannot eat breakfast, but you cannot even eat supper the night before. Even boiled water must be asked by the doctor before drinking it. Therefore, if you need to have a physical examination, you must ask the doctor about the arrangements and requirements for the examination before the examination.

Which tests require fasting?

Common examinations that require fasting include: barium meal, gastrointestinal endoscopy, pancreatic ultrasound, gallbladder-related examinations, blood sugar and blood lipid tests, and liver function tests.

Some examinations, such as laryngoscopy, gastroscopy, bronchoscopy, transesophageal echocardiography, etc., require fasting.

For some imaging examinations that require injection of contrast agents, such as enhanced CT and enhanced MRI, it is also recommended to fast.

Why fasting?

1. Impact Observation

When doing a barium meal, if there is food, it will appear as a black shadow protruding from the surface of the digestive tract, affecting the doctor's judgment.

Similarly, in gastroscopy, colonoscopy, etc., undigested food will become an obstacle to the advancement of the lens and block the doctor's field of view.

The pancreas is usually examined using ultrasound.

The pancreas is located behind the intestines, in the middle of the abdominal cavity. It cannot be observed from the back and is not close to the belly. Ultrasound examination requires passing through the belly and intestines to reach the pancreas.

After eating, a lot of air will be swallowed along with the food. The food and air will block the advancement of ultrasound. If the loss is too great, the sound waves will not be able to pass through the intestine and reach the dorsal side, which will also interfere with the observation of the pancreas.

As for the gallbladder examination, after eating, the gallbladder will contract in order to secrete bile, making it difficult to observe.

Therefore, the above examinations require fasting.

2. Interference with normal results

The ingredients in food can cause changes in blood composition, thereby interfering with the levels of some biochemical indicators and failing to accurately reflect the physical condition of the person being examined.

For example, indicators such as blood sugar and blood lipids will inevitably rise after eating.

However, some indicators such as insulin will fluctuate due to eating, which will interfere with the test results.

You should also ensure that you are fasting before doing a liver function test.

3. Avoid danger

In the throat, the trachea and esophagus are closely adjacent. If you eat something, vomitus may reach your mouth from your stomach and be accidentally inhaled into your trachea, causing choking or even suffocation, which is very dangerous.

Examinations such as laryngoscopy, gastroscopy, bronchoscopy, and transesophageal echocardiography may irritate the throat and may cause nausea and vomiting. In order to avoid danger, the examination is required on an empty stomach.

The same reason applies to fasting before surgical anesthesia, which is to prevent gastric contents from refluxing and vomiting into the trachea.

In addition, some imaging examinations, such as enhanced CT and enhanced MRI, require the injection of contrast agents. Contrast agents may cause allergies and subsequently induce vomiting. For safety reasons, it is recommended to have an empty stomach.