Platelets control clotting and stop bleeding, so when platelets are low, you bruise easily and bleeding doesn't stop easily even after a minor cut or scratch. (Women who are still having periods may have unusually heavy flow.) Nosebleeds and bleeding gums after brushing teeth can become an ongoing problem. Some people also get a rash that looks like little pinprick-sized red or purple dots, or they experience aching in their joints or muscles. Headaches are common too. For more information, see Understanding Low Platelets.