The fibrin deposition in coagulation can block blood vessels, leading to ischaemic damage to some tissues. As well as this, red blood cells are damaged as they get shredded by the fibrin.
There are a variety of causes of DIC, all usually causing the release of chemicals into the blood that instigates the coagulation.
Malignant cancers, or widespread tissue damage (e.g. burns), or hypersensivity reactions all can produce the chemicals leading to a DIC.
The underlying cause must be treated initially. Anticoagulants are not given as by now all the coagulation factors and platelets have been used up. These must be replaced, by platelet transfusion and fresh frozen plasma, to restore normal levels.
DIC results in lower fibrinogen (as it has all been converted to fibrin), and this can be tested for in the hospital lab. A more specific test is for "fibrin split products" which are produced when fibrin undergoes degradation when blood clots are dissolved by fibrinolysis.