Platelet Count

What is a platelet count?

A platelet count is a quick, common test that measures how many platelets are in your blood. Platelets, or thrombocytes, are tiny blood cells that bud from cells in the bone marrow (megakaryocytes). Platelets form clots when there’s damage to a blood vessel. For example, if you cut your finger, platelets mix with clotting factors (proteins in the blood). Together, they form a “glue” that stops the bleeding. There are tens of thousands of platelets in a single drop of blood.

A platelet count is usually part of a complete blood count. This test measures the number of platelets, white blood cells and red blood cells. The bone marrow makes blood cells.

When is a platelet count needed?

Your healthcare provider may order a platelet count during a routine physical examination. Or they may do the test if they think you have:

• Thrombocytopenia (low platelet count).
• Thrombocytosis (high platelet count).

How do I prepare for a platelet count?

Most people don’t need to do anything to prepare for a platelet count. In some cases, your healthcare provider may want you to fast (not eat or drink) before the test. Be sure to ask your provider if there are any instructions you should follow or medications to avoid before your blood test.

What happens during a platelet count?

The process to get blood for a platelet count only takes a few minutes. You may get the test at your healthcare provider’s office, a hospital or a lab. A provider called a lab technician usually takes blood samples.

The lab technician:

• Selects a vein on the inside of your arm, near your elbow.
• Puts a tourniquet (tight band or cord) around your upper arm. The tourniquet pushes blood down into your veins, making it easier to draw blood.
• Cleans the skin around your vein.
• Inserts a needle into your vein. You might feel a light stick and some discomfort.
• Fills a collection tube with blood.
• Removes the needle and tourniquet.
• Applies a small bandage to your arm.

A healthcare provider puts the blood in a small machine. The machine counts the platelets and other blood cells in about one minute.

In some cases, your provider may do a blood smear. This is an additional test to examine a small sample of blood under a microscope. A blood smear assesses the size and shape of blood cells.

Are there any risks with a platelet count?

A platelet count is a simple, common test. There are no significant risks. There may be a small amount of bleeding where the needle went into your vein. You might also see some light bruising or feel soreness on the inside of your arm.

What if I’m afraid of having my blood drawn?

Some people feel nervous around needles or before they have their blood drawn. This is natural. Try to breathe deeply to relax yourself during the test. It may help to look away from the needle as your blood is being drawn. You can also talk to someone during the test to distract yourself.

When will I know the results of the platelet count?

You may receive your results the same day as your blood test. Or you may need to wait about a week. Ask your healthcare provider when you can expect your results.

What do platelet count results mean?

Platelets are measured per microliter of blood:

• Normal platelet count range: Between 150,000 and 400,000 platelets per microliter.
• Low platelet count: Less than 150,000 platelets per microliter.
• High platelet count: More than 450,000 platelets per microliter.

What if I have a low platelet count?

Low platelets can prevent blood from clotting. This could be a result of:

• Bone marrow damage. Cancer treatments, such as chemotherapy or radiation therapy.
• Certain cancers, such as leukemia or lymphoma.
• Certain medications.
• Enlarged spleen.
• Heavy drinking (alcohol).
• Hemolytic uremic syndrome (a disease that destroys platelets).
• Immune thrombocytopenia (spots of bleeding or bruises under the skin due to low platelets).
• Severe bleeding after an injury.
• Thrombotic thrombocytopenic purpura (blood clots in small blood vessels throughout the body).
• Viral or bacterial infections.

Symptoms of too few platelets include:

• Blood in your vomit, urine or bowel movements.
• Bruising easily.
• Excessive bleeding from small cuts, gums or nosebleeds.
• Menorrhagia (heavy menstrual bleeding).
• Muscle or joint pain.
• Severe headaches.
• Weakness or dizziness.

What if I have a high platelet count?

A high platelet count can cause too much clotting in your blood vessels. Or it can cause too much bleeding if the platelets interfere with clotting. It could be a sign of:

• Immune system problems.
• Infections.
• Problems with the genes that control platelet production.
• Some cancers.

Symptoms and complications of too many platelets include:

• Bruising easily.
• Chest pain.
• Thrombosis (blood clotting when not required).
• Excessive bleeding from small cuts, gums or nosebleeds.
• Leg swelling.
• Shortness of breath.
• Stroke.
• Tingling or burning in your fingertips, hands and feet.
• Weakness, dizziness or fatigue.

A note from Cleveland Clinic

A platelet count is a quick, common test that counts the number of platelets in your blood. Platelets are cells that help your blood clot. A low platelet count might be a sign of certain cancers or infections. A high platelet count can put you at risk for harmful blood clots or stroke.