Normal count is in the range of 150×109 to 450×109 platelets per liter of blood,[1] but investigation is typically only considered if the upper limit exceeds 750×109/L.

Often, it occurs in tandem with an inflammatory disease as the principal stimulants of platelet production (e.g. thrombopoietin) are elevated in these clinical states as part of the acute phase reaction.

[citation needed] A very small number of people report symptoms of erythromelalgia, a burning sensation and redness of the extremities that resolves with cooling, or aspirin or both.

Other causes of reactive thrombocythemia include: post surgery, iron deficiency, drugs, and rebound effect after bone marrow suppression.

[8] Research suggests that thrombocytosis can also occur after physical exercise, and is triggered by hemoconcentration and the release of platelets from the liver, lungs and spleen.

[8] Laboratory tests might include: full blood count, liver enzymes, renal function and erythrocyte sedimentation rate.

In cases of reactive thrombocytosis of more than 1,000x109/L, it may be considered to administer daily low dose aspirin (such as 65 mg) to minimize the risk of stroke or thrombosis.