ABO typing:

If your blood cells stick together when mixed with:

• Anti-A serum, you have type A blood
• Anti-B serum, you have type B blood
• Both anti-A and anti-B serums, you have type AB blood

If your blood cells do not stick together when anti-A and anti-B are added, you have type O blood.

Back typing:

• If the blood clumps together only when B cells are added to your sample, you have type A blood.
• If the blood clumps together only when A cells are added to your sample, you have type B blood.
• If the blood clumps together when either types of cells are added to your sample, you have type O blood.

Lack of blood cells sticking together when your sample is mixed with both types of blood indicates you have type AB blood.

RH typing:

• If your blood cells stick together when mixed with anti-Rh serum, you have type Rh-positive blood.
• If your blood does not clot when mixed with anti-Rh serum, you have type Rh-negative blood.