There are many precautions to take when donating blood. Before donating blood, tests should be done to avoid the transmission of infectious diseases through blood, therefore, a certain amount of pre-donation should be done before donating blood. Pre-donation also means that the blood of certain donors should be taken first to quickly determine whether there are four tests such as hepatitis B, hepatitis C, syphilis and AIDS, etc. If there are none, then blood can be donated officially. If the blood pressure, breathing and pulse are normal, the donor can donate blood. However, those with substandard liver function or high blood lipids should not donate blood, and those who eat too much fat the night before donating blood should not eat too much. When you come to the blood donation site, you should relax and not be overly nervous. After donating blood, you should compress the needle holes for 5-10 minutes because the needles are relatively thick and you should try to compress the blood vessels after donating blood.