What happens if the hospital puts type a blood in a patient that has type b blood are different bloods compatible?

There. There are 4 basic blood types: a, b, ab, or o. Additionally, each blood type is either rh-positive or rh-negative. If you need a blood transfusion, there needs to be a match between your blood type and the transfusion blood type. People with type o blood are called universal donors because most people can receive type o blood. People with type ab blood are called universal recipients because usually they can receive a transfusion of the other blood types. A person with type a blood can donate blood to a person with type a or type ab blood and can receive blood from a person with type a or type o blood. A person with type b blood can donate blood to a person with type b or type ab and can receive blood from a person with type b or type o. A person with type ab blood can donate blood to a person with type ab and can receive blood from any of the blood types. A person with type o blood can donate to anyone and can receive blood from a person who has type o blood. If the blood types are not matched than antibodies in your body will attack the blood that has been transfused into you and you can become quite ill. If a person with blood type b receives a transfusion of type a blood, the blood cells may clump together and cause a serious reaction. If incompatible blood types are mixed it can cause a fatal reaction.