Platelets are components of blood that aid in the formation of blood clots. Thrombocytosis arises when the body produces an excessive number of platelets. When this excess is triggered by an underlying condition, such as an infection, it is termed reactive or secondary thrombocytosis.

In rare cases where no apparent cause is identified, it is labeled primary thrombocythemia or essential thrombocythemia, a condition affecting both blood and bone marrow. The detection of elevated platelet levels often involves a routine blood test known as a complete blood count. It is essential to differentiate between reactive thrombocytosis or essential thrombocythemia to determine the appropriate course of treatment.


Individuals with elevated platelet counts may exhibit no symptoms at all. When symptoms appear, blood clots are frequently the cause. As examples, consider:

  • Headache
  • Weakness
  • Pain in the chest
  • Confusion or speech changes
  • Burning pain in the hands or feet
  • Difficulty of breathing and nausea

Extremely elevated platelet levels can lead to bleeding, resulting in:

  • Bruises
  • Mouth or gum bleeding.
  • Bleeding of the nose
  • Blood in the stool.


Within your bones resides a spongy tissue known as bone marrow, containing stem cells capable of developing into platelets, white blood cells, or red blood cells. Platelets adhere to each other, aiding in the formation of a clot that halts bleeding when a blood vessel is injured, such as during a cut. However, an overproduction of platelets can result in thrombocytosis.

Reactive thrombocytosis

This kind of thrombocytosis is more typical. It is brought on by an underlying medical issue, like:

  • Cancer.
  • Infections.
  • Spleen removal.
  • Iron deficiency.
  • Traumas and surgeries.
  • Blood loss.
  • Hemolytic anemia — a form of anemia where the body creates less red blood cells than it can destroy, usually as a result of autoimmune disorders or specific blood diseases.
  • Inflammatory conditions such inflammatory bowel disease, sarcoidosis, and rheumatoid arthritis.

Essential thrombocythemia

The exact cause of this condition remains unclear, but it often appears to be associated with changes in specific genes. In thrombocytosis, the bone marrow produces an excessive amount of cells responsible for platelets formation, often resulting in dysfunctional platelets. Unlike reactive thrombocytosis, this form carries a higher risk of clotting or bleeding complications.