When someone is getting a blood thinner, how do doctors know how thin to make the blood?

That's a good question because it is possible to give too much of a blood thinner, or anticoagulant. When your doctor wants to give you an anticoagulant, he or she needs some tests done to see how long it takes for your blood to clot. There is a set amount of time that is considered to be normal. If the blood clots too quickly, this can cause blood clots inside your body that can cause severe damage, even death.

Once the doctor has determined that you do need an anticoagulant, then he or she has to decide what type to give you. Once you have begun to receive the anticoagulant, you will get blood tests frequently to monitor how effective the medication is. If your blood still takes longer than normal to clot, the doctor may increase your dose of anticoagulant. If your blood takes too long to clot, the doctor will lower the dose. Sometimes, there may be many dosage adjustments, sometimes they're rarely needed.