What if you mixed uncompatible blood types?

[Chubbs]

Would you get sick, or even die?

[Futile_Gesture]

Doesn’t go all clumpy? In which case you’d probably die of blood clots.

[Saltire]

I am not a doctor (or even a phlebotomist), but yes, you would.

The thing that makes blood types incompatible is that proteins on the surface of the cells can stick together with the proteins of other types (though they don’t stick to their own type). So, mixing incompatible types causes the blood to clump up, causing clots. If enough is put into a blood vessel, it can actually clog up the vessel. If the clot breaks loose, it can travel to the heart, brain or lungs, where a clot can really be life-threatening.

[Derleth]

From: http://www.bloodbook.com/type-sys.html :
**Transfusing a patient with the incorrect ABO group Blood may have fatal consequences. Donor red cells may be destroyed by an antibody in the recipient’s plasma. The rapid intravascular hemolysis which occurs in ABO incompatible transfusions can precipitate severe disseminated coagulation (DIC), prolonged hypotension, acute uraemia and even death. It has also been recognized that a potent anti-A or anti-B in donor Blood of group O may destroy the A or B red cells of a non-O recipient. This, together with the discovery of other red cell group systems, has completely altered the significance of the term ‘universal donor’ which is often applied to Blood of group O. **

Nasty, nasty stuff. DIC does mean that the blood goes ‘clumpy’ as globs of cells are formed. Hypotension is abnormally low blood pressure. Uraemia, or uremia, is where wastes normally excreted in urine build up in the bloodstream to toxic levels. So, yes, you can die from mismatched blood. Be very glad typing is such a well-developed science.