China advocates citizens to donate blood without compensation, but there are some cases where blood cannot be donated. The common reasons are: i. Minors below the age of 18 and elderly people older than 55 years old are not suitable for blood donation. II. People whose weight is not up to standard cannot donate blood. Adult males weighing less than 50kg and adult females weighing less than 45kg cannot donate blood due to low weight. People with high blood pressure cannot donate blood. Systolic blood pressure exceeds 140 mmHg and diastolic blood pressure exceeds 95 mmHg, which is not suitable for blood donation. IV. People with abnormal liver function cannot donate blood, such as those with increased transaminases. V. People with positive antibodies to various viruses cannot donate blood, such as those who are carriers of hepatitis B antigen, positive antibodies to hepatitis C, positive antibodies to AIDS and positive antibodies to syphilis cannot donate blood. Patients who are anemic cannot donate blood.