Hypogranular platelets (Gray platelets) are platelets characterized by reduced or absent granule content in the cytoplasm, giving them a grayish, pale appearance rather than the usual purple-granular aspect.

The absence of the granules may be due to activation of the platelet in the body (diffuse intravascular coagulation, DIS) or after sampling (aggregation, EDTA phenomenon). Thus, counting of degranulated platelets should always be done in detached platelets. Another possible cause is hereditary Gray Platelet Syndrome (GPS); a rare hereditary bleeding disorder characterized by large, gray platelets deficient in alpha-granules.