Hematocrit measures the percentage of red blood cells in blood and can indicate various medical conditions. It is measured through a blood test and abnormal levels can be a sign of disease. Complications are rare but possible. Normal levels vary by age and gender. An increase in hematocrit can be caused by lung disease or dehydration, while a decrease can be caused by blood loss or bone marrow disease. It can also be used to detect blood doping in athletes.
The hematocrit, or HCT, refers to the amount of red blood cells in the entire blood volume. It is measured in percentage. It is also sometimes referred to as packed cell volume. The hematocrit is measured through a blood test. Abnormal levels can be a sign of various diseases or medical conditions.
Often an HCT test is ordered as part of a complete blood count. It may be repeated several times to determine if certain conditions, such as anemia, are improving. The test involves drawing blood from a vein. A vein, often in the arm or hand, is cleaned out with an antiseptic. Next, a needle is inserted into the vein and blood is drawn.
Although blood tests are considered routine and rarely lead to complications, problems are possible. Infection can develop, especially if the site wasn’t cleaned well before blood was drawn. Other rare complications that can occur include excessive bleeding and a hematoma at the site.
Once blood has been drawn, it is analyzed using special laboratory equipment to determine the hematocrit. Laboratory equipment varies and different techniques may be used to obtain a measurement. Thick blood, containing red blood cells, will separate from the liquid component of blood after being centrifuged. This helps determine the percentage of the entire blood volume that contains red blood cells.
Normal levels vary according to the gender and age of the patient. For example, in newborns, normal values range from 55 to 68 percent. By age 10, 36 to 41 percent is considered normal. Normal ranges for male adults are 42 to 54 percent, and in adult females a normal number is 38 to 46 percent.
A low hematocrit level can indicate various conditions such as excessive blood loss or nutritional deficiency. Bone marrow diseases, such as leukemia, can also cause a decrease in red blood cells and result in a low hematocrit.
Various conditions can also cause an increase in hematocrit. Some lung diseases, such as chronic obstructive pulmonary disease, can cause an increased red blood cell ratio. Dehydration and being at high altitudes can also often lead to an increase in hematocrit.
Another reason to control HCT could be to control blood doping among athletes. When an athlete uses steroids, the drugs can increase the percentage of red blood cells in the body and raise the hematocrit above normal levels. A baseline HCT level is often taken on professional athletes to determine what their HCT rate is. This level is compared to random screenings done to check for blood doping.
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