It's an empty stomach in the morning, and there is no food to digest in the body. Energy supply mostly comes from glycogen decomposition, and the blood sugar of glycogen decomposition will reach a balanced state under the mediation of insulin and glucagon, maintaining normal physical strength and physical consumption. School physical examination is to draw more blood, and blood sugar can't be decomposed in a short time after blood drawing, which leads to short-term dysfunction, especially insufficient blood supply to the brain. Because the brain does not store less glycogen, the decomposition of glycogen in the body will be transported to the brain tissue through blood circulation, and you will feel dizzy and vomit in this short time. It is a normal phenomenon, please don't worry too much, it will bring psychological pressure!
You can prepare a cup of brown sugar water in advance in the future physical examination. It is ok to drink some brown sugar water after blood drawing, or you can eat a loaf of bread, which contains more sugar and can be digested quickly!