A critically low platelet count is anywhere between 10,000 to 20,000 platelets per microliter of circulating blood, according to MedicineNet.com. Spontaneous bleeding can occur when platelets are in this range.
Symptoms of a low platelet count include easy bruising, the development of a red or purplish pinpoint rash caused by bleeding under the skin, and prolonged bleeding from minor cuts or scrapes, notes Lab Tests Online. Individuals may also experience spontaneous nosebleeds, bleeding gums, and blood in the urine or stool. Women may also experience heavy or prolonged menstrual flow.
A low platelet count is called thrombocytopenia, explains Mayo Clinic. Normal levels of platelets range between 150,000 to 450,000 per microliter of circulating blood. Reasons for low levels vary, though they can be grouped into three broad categories: increased platelet destruction, reduced platelet production and the trapping of platelets in the spleen.
Causes of increased platelet destruction include medication side effects, bacterial blood infections and automimmune diseases, according to Mayo Clinic. Pregnancy may also cause mild drops in platelet counts. Reduced platelet production may be caused by chemotherapy or radiation treatment regimens, leukemias, and some forms of anemia. Exposure to noxious chemicals and some viral infections may also suppress platelet production. Additionally, an enlarged spleen can trap platelets, removing them from circulation and lowering platelet counts in the body.