A dangerous level of platelets depends on whether the count is too low or too high: Low Platelet Count (Thrombocytopenia):

• A platelet count below 150,000 per microliter of blood is considered low.
• Mild thrombocytopenia ranges from 100,000 to 150,000 platelets/µL.
• Moderate thrombocytopenia is 50,000 to 100,000 platelets/µL.
• Severe thrombocytopenia is below 50,000 platelets/µL.
• Dangerously low platelet counts are typically below 20,000 platelets/µL, where the risk of spontaneous and severe internal bleeding increases significantly. Counts below 10,000 platelets/µL are especially critical and can cause life-threatening bleeding

High Platelet Count (Thrombocytosis):

• A platelet count above 450,000 platelets/µL is considered high.
• High platelet counts can increase the risk of abnormal clotting, which may lead to strokes, heart attacks, or other serious complications.
• Symptoms of dangerously high platelet levels may include bruising, nosebleeds, chest pain, or stroke-like symptoms

In summary, platelet counts below 20,000 per microliter are dangerous due to bleeding risk, while counts above 450,000 per microliter can pose risks related to clotting. Medical evaluation is essential to determine the cause and appropriate treatment.