The normal platelet count for a child or an adult is between 150,000 and 400,000 platelets per microliter of blood, according to MedlinePlus. Any number above or below this range may be indicative of a health issue. A simple blood test can be performed by a doctor, to determine if platelet levels are within the normal range.
Platelets are compounds found in the blood that help the blood clot when there is an injury, states MedlinePlus. These cells are smaller than red blood cells and are crucial to a person's health. If a person has low platelets, they may have a higher risk of bleeding than the average person. If a person has too many platelets, they may be at risk for developing blood clots throughout their life.