Platelet Inhibition Study

ExitCare ImagePlatelets are a type of blood cell that helps the blood to clot. A platelet inhibition study is a test to determine how long it takes the blood to clot. Antiplatelet medicines inhibit the ability of platelets to form blood clots. These medicines make the blood "slippery" and help "thin" the blood. It is important to know how well the antiplatelet medicine is working. If the blood is too thin, this can increase the risk of bleeding. If the blood is not thin enough, the risk of developing a clot is increased.


People who take antiplatelet medicine will need a platelet inhibition study. This includes people who:

  • Have high risk coronary artery disease and take an antiplatelet medicine.

  • Have heart stents. A stent helps keep the heart arteries open so they can supply blood to the heart. In time, a stent can get blocked. One way to keep this from happening is to use antiplatelet medicine along with the stent. The medicine makes it less likely for blood clots to form. Using both medicine and a stent gives the best chance of avoiding a new blockage. That could prevent a heart attack or stroke. There are 2 types of stents commonly used:

  • Drug-eluting stents (DES). This kind of stent has a coating to help prevent scar tissue from growing over the stent. People who have drug-eluting stents may need to be on long-term antiplatelet therapy.

  • Bare metal stents. This kind of stent does not have a coating. Scar tissue grows over the stent. These types of stents usually do not need antiplatelet medicine.


The platelet inhibition study consists of drawing blood. The test will show how long it takes for your platelets to clot. Based on the test results, your caregiver may need to adjust your antiplatelet medicine.


  • Antiplatelet medicine must be taken exactly as prescribed. Follow your caregiver's instructions regarding how much to take and when to take it.

  • A platelet inhibition study might change the amount of antiplatelet medicine you take.

  • Frequent testing may be needed while you are taking antiplatelet medicine.

  • Keep a log of the medicine. Write down when you take it and how much is taken. This will help keep you from making mistakes.

  • Do not stop taking antiplatelet medicine unless your caregiver tells you to.

  • Stopping this medicine can cause a blood clot to form. That could lead to a heart attack or stroke.

  • Patients who take long-term aspirin or antiplatelet medicine should inform their caregiver before any medical procedures are performed. This includes dental work.

  • Make sure the caregiver who is in charge of your platelet inhibition study knows about any changes in other medicines that you take. Many other drugs can interfere with antiplatelet medicines. They include:

  • Proton pump inhibitors such as omprazole. This can affect the antiplatelet activity of some medicines.

  • Over-the-counter pain relievers such as nonsteroidal anti-inflammatory drugs (NSAIDS).

  • Other blood thinners.


  • You have stomach pain, headache, or nausea that does not go away.

  • You develop a rash or hives (red bumps on the skin that itch, sting, or burn).

  • You begin to bruise easily.

  • You have a cut that bleeds longer than normal.

  • You feel unusually weak, tired, or lightheaded.


  • You have a nosebleed or any other bleeding that does not stop.

  • You cough up or vomit blood or anything that looks like coffee grounds.

  • You have a bowel movement that looks bloody, black, or tarry.

  • You have chest pain.

  • Your breathing becomes difficult.

  • You have a severe headache that comes on suddenly.

  • You become confused or have trouble seeing, talking, or keeping your balance.

  • You suddenly develop weakness or numbness.

  • Your mouth or throat swells. This can make breathing or swallowing difficult.

  • You have a fever.


  • Understand these instructions.

  • Will watch your condition.

  • Will get help right away if you are not doing well or get worse.