What are the problems with a high hematocrit?

High hematocrit scores are symptomatic of several serious conditions, including congenital heart disease, heart failure on the right side, lung scarring, bone marrow disease and blood abnormalities, according to MedlinePlus. Dehydration sometimes causes high readings as well.

Hematocrit blood tests determine the percentage of red blood cells within whole blood, explains MedlinePlus. The measurement is based on both the number and size of red blood cells. Hematocrit tests are typically requested when patients show symptoms of anemia, dietary deficiencies or leukemia.

Results are sometimes affected by high altitude, pregnancy and recent blood loss or transfusion, Mayo Clinic observes. In women, normal results range from 34.9 to 44.5 percent, while men's are between 38.8 and 50 percent.