Home > Health A – Z > Thrombocytopenia


A condition in which there is a lower-than-normal number of platelets in the blood. It may result in easy bruising and excessive bleeding from wounds or bleeding in mucous membranes and other tissues. NIH - National Cancer Institute


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... Read more about Thrombocytopenia

What works? Research summarized

Evidence reviews

Risk for heparin-induced thrombocytopenia with unfractionated and low-molecular-weight heparin thromboprophylaxis: a meta-analysis

Heparin-induced thrombocytopenia (HIT) is an uncommon but potentially devastating complication of anticoagulation with unfractionated heparin (UFH) or low-molecular-weight heparin (LMWH). Our objective was to determine and compare the incidences of HIT in surgical and medical patients receiving thromboprophylaxis with either UFH or LMWH. All relevant studies identified in the MEDLINE database (1984-2004), not limited by language, and from reference lists of key articles were evaluated. Randomized and nonrandomized controlled trials comparing prophylaxis with UFH and LMWH and measuring HIT or thrombocytopenia as outcomes were included. Two reviewers independently extracted data on thromboprophylaxis (type, dose, frequency, and duration), definition of thrombocytopenia, HIT assay, and rates of the following outcomes: HIT, thrombocytopenia, and thromboembolic events. HIT was defined as a decrease in platelets to less than 50% or to less than 100 x 10(9)/L and positive laboratory HIT assay. Fifteen studies (7287 patients) were eligible: 2 randomized controlled trials (RCTs) measuring HIT (1014 patients), 3 prospective studies (1464 patients) with nonrandomized comparison groups in which HIT was appropriately measured in both groups, and 10 RCTs (4809 patients) measuring thrombocytopenia but not HIT. Three analyses were performed using a random effects model and favored the use of LMWH: (1) RCTs measuring HIT showed an odds ratio (OR) of 0.10 (95% confidence interval [CI], 0.01-0.2; P = .03); (2) prospective studies measuring HIT showed an OR of 0.10 (95% CI, 0.03-0.33; P < .001); (3) all 15 studies measured thrombocytopenia. The OR was 0.47 (95% CI, 0.22-1.02; P = .06). The inverse variance-weighted average that determined the absolute risk for HIT with LMWH was 0.2%, and with UFH the risk was 2.6%. Most studies were of patients after orthopedic surgery.

Rituximab for children with immune thrombocytopenia: a systematic review

BACKGROUND: Rituximab has been widely used off-label as a second line treatment for children with immune thrombocytopenia (ITP). However, its role in the management of pediatric ITP requires clarification. To understand and interpret the available evidence, we conducted a systematic review to assess the efficacy and safety of rituximab for children with ITP.

How frequently is venous thromboembolism in heparin-treated patients associated with heparin-induced thrombocytopenia?

This review assessed the frequency of heparin-induced thrombocytopenia (HIT) associated with venous thromboembolism in patients given unfractionated or low molecular weight heparin for thromboprophylaxis or treatment. The authors concluded that unfractionated but not low molecular weight heparin is associated with high-frequency HIT. Poor reporting, inadequate literature searches, failure to address study quality and inappropriate synthesis mean that the authors' conclusions are unlikely to be reliable.

See all (332)

Summaries for consumers

Antenatal interventions for fetomaternal alloimmune thrombocytopenia

The optimal management of pregnant women with a previous child affected by fetomaternal alloimmune thrombocytopenia remains unclear.

Frequency of heparin‐induced thrombocytopenia in postoperative patients according to type of heparin

Heparin is a natural agent with antithrombotic action. Two types of heparins are widely used, unfractionated heparin (UFH) and low molecular weight heparin (LMWH). Heparin‐induced thrombocytopenia (HIT) is an adverse reaction that can occur during treatment with heparin. It is common in practice and its most important consequence is a paradoxical increase in the risk of thromboembolic complications. The frequency of HIT is still poorly understood. A number of factors are thought to influence its frequency, including the type of heparin and the type of patient exposed; postoperative patients are at higher risk. This review aimed to compare the risk of HIT in postoperative patients exposed to UFH or LMWH. A better understanding of this problem should contribute to safer management of postoperative patients who need thromboprophylaxis with heparin.

Drug therapy for treating idiopathic thrombocytopenic purpura during pregnancy

Idiopathic thrombocytopenic purpura (ITP) is an immune‐mediated hematologic disorder caused by a low blood platelet count (thrombocytopenia). Antiplatelet antibodies act against the platelets resulting in platelet destruction by the spleen. In adults, the clinical features of ITP often have an insidious onset and are highly variable, ranging from no symptoms, mild bruising, to mucosal bleeding, and skin discolorations. Management of ITP during pregnancy is complex because of large differences between maternal and fetal platelet counts. The circulating antibodies can cross the placenta and cause a neonatal passive immune thrombocytopenia that may increase the risk of cerebral haemorrhage in the newborn infant. For this reason, it seems reasonable that cesarean section delivery is safer for the infant than vaginal delivery yet the mode of delivery may not affect the rate of haemorrhage. Many different pharmacological interventions are used for treating this medical disorder and treatment for ITP in pregnant women is not standardised. Some of these drugs have potential side effects for pregnant women and some can cause fetal malformation.

See all (42)

Terms to know

A tissue with red blood cells, white blood cells, platelets, and other substances suspended in fluid called plasma. Blood takes oxygen and nutrients to the tissues, and carries away wastes.
Bone Marrow
The soft, sponge-like tissue in the center of most bones. It produces white blood cells, red blood cells, and platelets.
Mucosa (Mucous Membranes)
The moist, inner lining of some organs and body cavities (such as the nose, mouth, lungs, and stomach). Glands in the mucosa make mucus (a thick, slippery fluid). Also called mucous membrane.
Platelets (Thrombocytes)
A tiny piece of cell that is made by breaking off of a large cell in the bone marrow. Platelets are found in the blood and spleen. They help form blood clots to slow or stop bleeding, and to help wounds heal. Also called thrombocyte.
A group of cells that act together to carry out a specific function in the body. Examples include muscle tissue, nervous system tissue (including the brain, spinal cord, and nerves), and connective tissue (including ligaments, tendons, bones, and fat). Organs are made up of tissues.

More about Thrombocytopenia

Photo of an adult

Also called: Thrombocytopenic disorder

Other terms to know: See all 5
Blood, Bone Marrow, Mucosa (Mucous Membranes)

Keep up with systematic reviews on Thrombocytopenia:


PubMed Health Blog...

read all...