A platelet count is used to detect a low or high number of platelets in the blood. The test is included in a complete blood count (CBC), a panel of tests often performed as part of a general health examination. A platelet count may be used to screen for or diagnose various diseases and conditions that affect the number of platelets in the blood. It may be used as part of the workup of a bleeding disorder, bone marrow disease, or excessive clotting disorder. The test may used as a monitoring tool for people with underlying conditions or undergoing treatment with drugs known to affect platelets. It may also be used to monitor those being treated for a platelet disorder to determine if therapy is effective. A platelet count may be performed in conjunction with one or more platelet function tests, which assess the function of platelets, and other tests that evaluate coagulation such as PT and PTT. If results are not within the normal interval, a number of other tests may be performed to help give clues as to the cause.