Thrombocytopenia (THROM-bo-si-to-PE-ne-ah) is a condition in which your blood has a lower than normal number of blood cell fragments called platelets (PLATE-lets).
Platelets are made in your bone marrow along with other kinds of blood cells. They travel through your blood vessels and stick together (clot) to stop any bleeding that may happen if a blood vessel is damaged. Platelets also are called thrombocytes (THROM-bo-sites) because a clot also is called a thrombus.
When your blood has too few platelets, mild to serious bleeding can occur. Bleeding can occur inside your body (internal bleeding) or underneath your skin or from the surface of your skin (external bleeding).
A normal platelet count in adults ranges from 150,000 to 450,000 platelets per microliter of blood. A platelet count of less than 150,000 platelets per microliter is lower than normal. If your blood platelet count falls below normal, you have thrombocytopenia.
However, the risk for serious bleeding doesn't occur until the count becomes very low—less than 10,000 or 20,000 platelets per microliter. Mild bleeding sometimes occurs when the count is less than 50,000 platelets per microliter.
Many factors can cause a low platelet count, such as:
How long thrombocytopenia lasts depends on its cause. It can last from days to years.
The treatment for this condition also depends on its cause and severity. Mild thrombocytopenia often doesn't require treatment. If the condition causes or puts you at risk for serious bleeding, you may need medicines or blood or platelet transfusions. Rarely, the spleen may need to be removed.
Thrombocytopenia can be fatal, especially if the bleeding is severe or occurs in the brain. However, the overall outlook for people who have the condition is good, especially if the cause of the low platelet count is found and treated.
Many factors can cause thrombocytopenia (a low platelet count). The condition can be inherited or acquired. "Inherited" means your parents pass the gene for the condition to you. "Acquired" means you aren't born with the condition, but you develop it. Sometimes the cause of thrombocytopenia isn't known.
In general, a low platelet count occurs because:
A combination of the above factors also may cause a low platelet count.
Bone marrow is the sponge-like tissue inside the bones. It contains stem cells that develop into red blood cells, white blood cells, and platelets. When stem cells are damaged, they don't grow into healthy blood cells.
Many conditions and factors can damage stem cells.
Cancer, such as leukemia (lu-KE-me-ah) or lymphoma (lim-FO-ma), can damage the bone marrow and destroy blood stem cells. Cancer treatments, such as radiation and chemotherapy, also destroy the stem cells.
Aplastic anemia is a rare, serious blood disorder in which the bone marrow stops making enough new blood cells. This lowers the number of platelets in your blood.
Exposure to toxic chemicals—such as pesticides, arsenic, and benzene—can slow the production of platelets.
Some medicines, such as diuretics and chloramphenicol, can slow the production of platelets. Chloramphenicol (an antibiotic) rarely is used in the United States.
Common over-the-counter medicines, such as aspirin or ibuprofen, also can affect platelets.
Alcohol also slows the production of platelets. A temporary drop in the platelet count is common among heavy drinkers, especially if they're eating foods that are low in iron, vitamin B12, or folate.
Chickenpox, mumps, rubella, Epstein-Barr virus, or parvovirus can decrease your platelet count for a while. People who have AIDS often develop thrombocytopenia.
Some genetic conditions can cause low numbers of platelets in the blood. Examples include Wiskott-Aldrich and May-Hegglin syndromes.
A low platelet count can occur even if the bone marrow makes enough platelets. The body may destroy its own platelets due to autoimmune diseases, certain medicines, infections, surgery, pregnancy, and some conditions that cause too much blood clotting.
Autoimmune diseases occur if the body's immune system mistakenly attacks healthy cells in the body. If an autoimmune disease destroys the body's platelets, thrombocytopenia can occur.
One example of this type of autoimmune disease is immune thrombocytopenia (ITP). ITP is a bleeding disorder in which the blood doesn't clot as it should. An autoimmune response is thought to cause most cases of ITP.
Normally, your immune system helps your body fight off infections and diseases. But if you have ITP, your immune system attacks and destroys its own platelets. Why this happens isn't known. (ITP also may occur if the immune system attacks your bone marrow, which makes platelets.)
Other autoimmune diseases that destroy platelets include lupus and rheumatoid arthritis.
A reaction to medicine can confuse your body and cause it to destroy its platelets. Examples of medicines that may cause this to happen include quinine; antibiotics that contain sulfa; and some medicines for seizures, such as Dilantin,® vancomycin, and rifampin. (Quinine is a substance often found in tonic water and nutritional health products.)
Heparin is a medicine commonly used to prevent blood clots. But an immune reaction may trigger the medicine to cause blood clots and thrombocytopenia. This condition is called heparin-induced thrombocytopenia (HIT). HIT rarely occurs outside of a hospital.
In HIT, the body's immune system attacks a substance formed by heparin and a protein on the surface of the platelets. This attack activates the platelets and they start to form blood clots.
A low platelet count can occur after blood poisoning from a widespread bacterial infection. A virus, such as mononucleosis or cytomegalovirus, also can cause a low platelet count.
About 5 percent of pregnant women develop mild thrombocytopenia when they're close to delivery. The exact cause isn't known for sure.
TTP is a rare blood condition. It causes blood clots to form in the body's small blood vessels, including vessels in the brains, kidneys, and heart.
DIC is a rare complication of pregnancy, severe infections, or severe trauma. Tiny blood clots form suddenly throughout the body.
In both conditions, the blood clots use up many of the blood's platelets.
Usually, one-third of the body's platelets are held in the spleen. If the spleen is enlarged, it will hold on to too many platelets. This means that not enough platelets will circulate in the blood.
An enlarged spleen often is due to cancer or severe liver disease, such as cirrhosis (sir-RO-sis). Cirrhosis is a disease in which the liver is scarred. This prevents it from working well.
An enlarged spleen also might be due to a bone marrow condition, such as myelofibrosis (MI-eh-lo-fi-BRO-sis). With this condition, the bone marrow is scarred and isn't able to make blood cells.
People who are at highest risk for thrombocytopenia are those affected by one of the conditions or factors discussed in "What Causes Thrombocytopenia?" This includes people who:
People at highest risk also include heavy alcohol drinkers and pregnant women.
Mild to serious bleeding causes the main signs and symptoms of thrombocytopenia. Bleeding can occur inside your body (internal bleeding) or underneath your skin or from the surface of your skin (external bleeding).
Signs and symptoms can appear suddenly or over time. Mild thrombocytopenia often has no signs or symptoms. Many times, it's found during a routine blood test.
Check with your doctor if you have any signs of bleeding. Severe thrombocytopenia can cause bleeding in almost any part of the body. Bleeding can lead to a medical emergency and should be treated right away.
External bleeding usually is the first sign of a low platelet count. External bleeding may cause purpura (PURR-purr-ah) or petechiae (peh-TEE-key-ay). Purpura are purple, brown, and red bruises. This bruising may happen easily and often. Petechiae are small red or purple dots on your skin.
Other signs of external bleeding include:
A lot of bleeding after surgery or dental work also might suggest a bleeding problem.
Heavy bleeding into the intestines or the brain (internal bleeding) is serious and can be fatal. Signs and symptoms include:
Your doctor will diagnose thrombocytopenia based on your medical history, a physical exam, and test results. A hematologist also may be involved in your care. This is a doctor who specializes in diagnosing and treating blood diseases and conditions.
Once thrombocytopenia is diagnosed, your doctor will begin looking for its cause.
Your doctor may ask about factors that can affect your platelets, such as:
Your doctor will do a physical exam to look for signs and symptoms of bleeding, such as bruises or spots on the skin. He or she will check your abdomen for signs of an enlarged spleen or liver. You also will be checked for signs of infection, such as a fever.
Your doctor may recommend one or more of the following tests to help diagnose a low platelet count. For more information about blood tests, go to the Health Topics Blood Tests article.
A complete blood count (CBC) measures the levels of red blood cells, white blood cells, and platelets in your blood. For this test, a small amount of blood is drawn from a blood vessel, usually in your arm.
If you have thrombocytopenia, the results of this test will show that your platelet count is low.
A blood smear is used to check the appearance of your platelets under a microscope. For this test, a small amount of blood is drawn from a blood vessel, usually in your arm.
Bone marrow tests check whether your bone marrow is healthy. Blood cells, including platelets, are made in your bone marrow. The two bone marrow tests are aspiration (as-pih-RA-shun) and biopsy.
Bone marrow aspiration might be done to find out why your bone marrow isn't making enough blood cells. For this test, your doctor removes a sample of fluid bone marrow through a needle. He or she examines the sample under a microscope to check for faulty cells.
A bone marrow biopsy often is done right after an aspiration. For this test, your doctor removes a sample of bone marrow tissue through a needle. He or she examines the tissue to check the number and types of cells in the bone marrow.
If a bleeding problem is suspected, you may need other blood tests as well. For example, your doctor may recommend PT and PTT tests to see whether your blood is clotting properly.
Your doctor also may suggest an ultrasound to check your spleen. An ultrasound uses sound waves to create pictures of your spleen. This will allow your doctor to see whether your spleen is enlarged.
Treatment for thrombocytopenia depends on its cause and severity. The main goal of treatment is to prevent death and disability caused by bleeding.
If your condition is mild, you may not need treatment. A fully normal platelet count isn't necessary to prevent bleeding, even with severe cuts or accidents.
Thrombocytopenia often improves when its underlying cause is treated. People who inherit the condition usually don't need treatment.
If a reaction to a medicine is causing a low platelet count, your doctor may prescribe another medicine. Most people recover after the initial medicine has been stopped. For heparin-induced thrombocytopenia (HIT), stopping the heparin isn't enough. Often, you'll need another medicine to prevent blood clotting.
If your immune system is causing a low platelet count, your doctor may prescribe medicines to suppress the immune system.
If your thrombocytopenia is severe, your doctor may prescribe treatments such as medicines, blood or platelet transfusions, or splenectomy.
Your doctor may prescribe corticosteroids, also called steroids for short. Steroids may slow platelet destruction. These medicines can be given through a vein or by mouth. One example of this type of medicine is prednisone.
The steroids used to treat thrombocytopenia are different from illegal steroids taken by some athletes to enhance performance.
Your doctor may prescribe immunoglobulins or medicines like rituximab to block your immune system. These medicines are given through a vein. He or she also may prescribe other medicines, such as eltrombopag or romiplostim, to help your body make more platelets. The former comes as a tablet to take by mouth and the latter is given as an injection under the skin.
Blood or platelet transfusions are used to treat people who have active bleeding or are at a high risk of bleeding. During this procedure, a needle is used to insert an intravenous (IV) line into one of your blood vessels. Through this line, you receive healthy blood or platelets.
For more information about this procedure, go to the Health Topics Blood Transfusion article.
A splenectomy is surgery to remove the spleen. This surgery may be used if treatment with medicines doesn't work. This surgery mostly is used for adults who have immune thrombocytopenia (ITP). However, medicines often are the first course of treatment.
Whether you can prevent thrombocytopenia depends on its specific cause. Usually the condition can't be prevented. However, you can take steps to prevent health problems associated with thrombocytopenia. For example:
If you have thrombocytopenia, watch for any signs and symptoms of bleeding. Report these signs and symptoms to your doctor right away.
Symptoms can appear suddenly or over time. Severe thrombocytopenia can cause bleeding in almost any part of the body. Bleeding can lead to a medical emergency and should be treated right away.
You can take steps to avoid health problems associated with thrombocytopenia. Be aware of the medicines you’re taking, avoid injuries, and contact your doctor if you have a fever or other signs or symptoms of an infection.
Avoid medicines that may affect your platelets and raise your risk of bleeding. Two examples of such medicines are aspirin and ibuprofen. These medicines may thin your blood too much. Be careful when using over-the-counter medicines—many contain aspirin or ibuprofen.
Tell your doctor about all of the medicines you take, including over-the-counter medicines, vitamins, supplements, and herbal remedies.
Avoid injuries that can cause bruising and bleeding. Don't take part in contact sports such as boxing, football, or karate. These sports are likely to lead to injuries that can cause bleeding.
Other sports, such as skiing or horseback riding, also put you at risk for injuries that can cause bleeding. Ask your doctor about physical activities that are safe for you.
Take safety precautions, such as using a seatbelt while riding in a car and wearing gloves when working with knives and other tools.
If your child has thrombocytopenia, try to protect him or her from injuries, especially head injuries that can cause bleeding in the brain. Ask your child's doctor whether you need to restrict your child's activities.
If you've had your spleen removed, you may be more likely to become ill from certain types of infection. Watch for fever or other signs of infection and report them to your doctor promptly. People who have had their spleens removed may need vaccines to prevent certain infections.
The National Heart, Lung, and Blood Institute (NHLBI) is strongly committed to supporting research aimed at preventing and treating heart, lung, and blood diseases and conditions and sleep disorders.
NHLBI-supported research has led to many advances in medical knowledge and care. Often, these advances depend on the willingness of volunteers to take part in clinical trials.
Clinical trials test new ways to prevent, diagnose, or treat various diseases and conditions. For example, new treatments for a disease or condition (such as medicines, medical devices, surgeries, or procedures) are tested in volunteers who have the illness. Testing shows whether a treatment is safe and effective in humans before it is made available for widespread use.
By taking part in a clinical trial, you can gain access to new treatments before they're widely available. You also will have the support of a team of health care providers, who will likely monitor your health closely. Even if you don't directly benefit from the results of a clinical trial, the information gathered can help others and add to scientific knowledge.
If you volunteer for a clinical trial, the research will be explained to you in detail. You'll learn about treatments and tests you may receive, and the benefits and risks they may pose. You'll also be given a chance to ask questions about the research. This process is called informed consent.
If you agree to take part in the trial, you'll be asked to sign an informed consent form. This form is not a contract. You have the right to withdraw from a study at any time, for any reason. Also, you have the right to learn about new risks or findings that emerge during the trial.
For more information about clinical trials related to thrombocytopenia, talk with your doctor. You also can visit the following Web sites to learn more about clinical research and to search for clinical trials:
For more information about clinical trials for children, visit the NHLBI's Children and Clinical Studies Web page.
The NHLBI updates Health Topics articles on a biennial cycle based on a thorough review of research findings and new literature. The articles also are updated as needed if important new research is published. The date on each Health Topics article reflects when the content was originally posted or last revised.