What Are Platelets?
Platelets (also called thrombocytes) are small blood cell fragments made by your bone marrow. They help form blood clots to stop you from bleeding when you've been injured.
If you have a lower than typical platelet count, it's called thrombocytopenia. This can happen due to different conditions, infections, some medicines, and some surgeries.
If you have a higher than typical platelet count, it can be caused by genetic mutations that make your bone marrow produce more platelets. This is called primary thrombocythemia. If it's caused by an underlying disorder that triggers the stem cells in your bone marrow to make more platelets, it's called secondary thrombocytosis.
You may or may not have symptoms if you have an abnormal platelet level. If you do, they usually include bleeding or blood clots.
Read on to learn more about a blood platelet count.
What Is a Platelet Count?
A platelet count measures the number of platelets in your blood. It's usually done as part of a complete blood count (CBC), which measures the number of white blood cells, red blood cells, and platelets in your blood.
Normal platelet count
Platelets generally make up less than 1% of your total blood volume. A healthy platelet count ranges from 150,000 to 450,000 platelets per microliter of blood.
Low platelet count (thrombocytopenia)
If your platelet count is fewer than 150,000 per microliter of blood, that means you have a low platelet count. Your doctor may call this thrombocytopenia. If you're injured, you may not have enough platelets to form a blood clot and stop the bleeding.
You may not have any symptoms with a low platelet count. Your doctor may discover you have it when you go in for a routine blood test. Whether or not you have symptoms depends on how low your platelet count is and what's causing it.
If you do have symptoms, they include:
- Bruises that form easily
- Bleeding from your gums or nose, or bleeding for a long time after even a small injury
- Signs of internal bleeding, such as blood in your pee, poop, or vomit (or black poop or vomit that looks like coffee grounds)
- Small, flat, red spots under your skin (also called petechiae), indicating possible blood leakage from blood vessels
- Red, purple, or brownish-yellow spots on your skin (also called purpura), which may suggest bleeding under the skin
- A swollen spleen or liver
- Fatigue
- Weakness and confusion
- Heavy menstrual periods
Low platelet count causes
You may have a low platelet count because:
- Your bone marrow doesn't make enough platelets.
- Your body uses or breaks them down too fast.
- Your spleen doesn't release them when you need them.
Your spleen is an organ in your belly that stores about a third of all your platelets and helps your immune system fight infections.
Some conditions that can cause low platelet count include:
- Aplastic anemia. This is a rare blood disorder that happens when your bone marrow can't make enough blood cells for you to function well.
- Anemia from vitamin deficiencies, such as vitamin B12 and folate deficiency. This can make it harder for your bone marrow to make enough platelets.
- Blood cancers, such as leukemia or lymphoma. These can damage your bone marrow, making it unable to make new platelets. Some cancer treatments, such as chemotherapy and radiation therapy, may also damage your bone marrow.
- Autoimmune conditions, such as lupus, rheumatoid arthritis, and immune thrombocytopenia. These can make your body attack your platelets and destroy them by mistake.
- Thrombotic thrombocytopenic purpura, hemolytic-uremic syndrome, and disseminated intravascular coagulation. These conditions can be triggered by cancer, blood poisoning, traumatic brain injury, and complications from childbirth. And they cause blood clots even when you haven't been injured, which can use up all your platelets.
- Bacterial and viral infections, such as HIV and hepatitis C. Some vaccines, such as for measles, mumps, and rubella, influenza, hepatitis B, and COVID-19. These infections can make your body destroy your platelets.
- Some medicines. Certain drugs, such as heparin, quinine, some diabetes medications, and antibiotics like trimethoprim/sulfamethoxazole, rifampin, and vancomycin, can make your body destroy your platelets.
- Cirrhosis of the liver, myelofibrosis, and Gaucher disease. These conditions can make your spleen swell, which may trap your platelets inside your spleen.
- Some surgeries, such as cardiopulmonary bypass surgery, which can make your body use up your platelets.
- Heavy alcohol use. It can keep your bone marrow from making the platelets you need.
- Having a large red blood cell replacement or exchange transfusion. Stored red blood cells don't have many platelets in them, so if you need a large transfusion of red blood cells, it can dilute the platelets currently circulating in your blood.
High platelet count
If your platelet count is higher than 450,000 per microliter of blood, then you have a high platelet count. A high platelet count can cause blood clots to form in any of your blood vessels, which can lead to deep vein thrombosis, pulmonary embolism, stroke, and heart attack. You may be more likely to develop complications from blood clots if you have conditions such as diabetes and high blood pressure that can damage your blood vessels.
If your doctor can't find another health condition that caused your high platelet count, it's called primary or essential thrombocythemia. If it's caused by another condition, it's called secondary or reactive thrombocytosis. Secondary thrombocytosis is more common than thrombocythemia.
Primary thrombocythemia is when the stem cells in your bone marrow that make platelets grow excessively. This can happen because of mutations in your genes that happen over time. You're more likely to have symptoms with thrombocythemia than with thrombocytosis. Symptoms include:
- Redness or discoloration, warmth, and a tingling or burning sensation in your hands and feet (caused by blood clots in your small vessels)
- Chest pain
- Loss of vision or seeing spots and floaters
- Headaches
- Weakness
- Dizziness
- Bleeding, including nosebleeds, easy bruising, and bleeding from your gums and digestive tract
Secondary thrombocytosis is when an underlying disorder triggers the stem cells in your bone marrow to make more platelets. It's unlikely you'll have symptoms from secondary thrombocytosis.
Conditions that can cause secondary thrombocytosis include:
- Inflammatory disorders, including rheumatoid arthritis and inflammatory bowel disease
- Certain cancers
- Premature destruction of your red blood cells (hemolysis)
- Iron deficiency
- Sarcoidosis
- Infections
- Trauma
- Surgery
- Removal of your spleen
- Excessive bleeding
Getting a Platelet Count
When to get a platelet count
You usually have a platelet count done as part of a complete blood count (CBC), which measures the number of white blood cells, red blood cells, and platelets in your blood. Most doctors will order a CBC as part of your routine physical exam. But your doctor may order one specifically if you have symptoms, such as:
- Uncontrolled bleeding from minor cuts
- Regular nosebleeds
- Red or purple spots on the skin
- Easy bruising
Some factors that can affect your platelet levels include:
- Altitude levels where you live
- Physical activity
- Certain medications
- Menstrual cycle
Platelet count preparation
There are no special requirements that you need to prepare for when you get a platelet count done. Since a platelet count is usually done as part of other blood testing, you may need to fast or limit your water intake. Your doctor can let you know if that's the case, but be sure to ask, especially if you take medicines every day. They may want you to wait to take your medicine until after the test.
Platelet count procedure
Platelet counts are relatively noninvasive and quick. Your provider will take a small blood sample from one of your veins and then put the sample in a tube or vial. This usually takes around five minutes.
There is very little that can go wrong in this test. At most, you might feel some pain and have minor bruising where the needle went in.
Platelet count results
You may get your platelet count results within a week. Depending on the procedure your doctor's office follows, you may get a letter with your results, or it may come to you through an online patient portal. On your lab report, you will see the number of platelets (PLT) in your blood, and you may also see the average size (called mean platelet volume or MPV).
Platelet count false readings
Occasionally, you could get a false result if your platelets stick together in a clump. The lab equipment that counts your blood cells can't count all the platelets in a clump, so the result will show fewer platelets than you actually have.
Takeaways
Platelets are small cell fragments in your blood that help form blood clots to stop the bleeding when you're injured. You'll usually get a platelet count as part of a routine blood test called a complete blood count. Your platelet levels can be either lower or higher than normal. Abnormal platelet levels can cause symptoms such as too many blood clots or excessive bleeding, although you may not have any symptoms at all. Whether you need treatment and the type of treatment will depend on what is causing your low or high platelet counts and how it's affecting you.
Platelet Count FAQs
How do you raise your platelet levels when you have a low platelet count?
Treatment for low platelet levels depends on what caused it, the severity of your symptoms, and how much they affect your daily life. If your low platelet count is caused by a medicine you're taking, your doctor will likely change your prescription to a different one. That may be enough to raise your platelet levels. Your doctor can also try a few prescriptions to help raise your levels, such as:
- Corticosteroids such as prednisone, which can raise your platelet levels
- Eltrombopag and romiplostim, which can help your body make more platelets
- Immunoglobulin and rituximab, which work by preventing your body from destroying platelets
If medicines don't work, your doctor may recommend a blood or platelet transfusion or surgery to remove your spleen (splenectomy), which may help raise your levels.