Several factors can cause a drop in hematocrit (HCT). The most common cause is anemia, which can be due to nutritional deficiencies (e.g., iron, vitamin B12, folate), chronic diseases, bleeding, or bone marrow disorders. Certain medications, such as chemotherapy drugs or immunosuppressants, can also lower HCT. Additionally, factors like pregnancy, overhydration, or diluted blood samples can temporarily lower HCT. Identifying the underlying cause of low HCT requires medical evaluation and appropriate diagnostic tests.