This page helps you to understand blood test results for Hematocrit (HCT) and gives you the reference range to determine if your lab test results mean that you have a high, low or normal Hematocrit (HCT).
We outline the risk factors associated with both raised and lower Hematocrit (HCT) levels.
Reference Ranges for Hematocrit (HCT) in men (please sign up to see ranges for women):
|US Conventional Units||%||34.9-44.5||<34.9 or >44.5|
|Standard International Units||%||34.9-44.5||<34.9 or >44.5|
What is Hematocrit (HCT)
Hematocrit is a test that measures the proportion of a person’s blood that is made up of red blood cells (RBCs). Blood consists of RBCs, white blood cells (WBCs), and platelets suspended in a fluid portion called plasma. The hematocrit is a ratio of the volume of red blood cells to the volume of all these components together, called whole blood. The value is expressed as a percentage or fraction. For example, a hematocrit value of 40% means that there are 40 milliliters of red blood cells in 100 milliliters of blood .
Since a hematocrit is often performed as part of a complete blood count (CBC), results from other components are taken into consideration.
Function of Hematocrit (HCT)
The hematocrit reflects both the number of red blood cells and their volume (mean corpuscular volume or MCV). If the size of the RBCs decreases, so will the hematocrit and vice versa. In general, the hematocrit will rise when the number of red blood cells increases and the hematocrit will fall to less than normal when there is a drop in production of RBCs by the bone marrow, an increase in the destruction of RBCs, or if blood is lost due to bleeding. If the bone marrow is not able to produce new RBCs fast enough, then the overall number of RBCs and hematocrit will drop .
Risk factors associated with Hematocrit (HCT)
Several diseases and conditions can affect RBCs and consequently the level of haemoglobin in the blood and haematocrit.
In general, the hemoglobin level and hematocrit rise when the number of red blood cells increases. The hemoglobin level and hematocrit fall to less than normal when there is a drop in production of RBCs by the bone marrow, an increase in the destruction of RBCs, or if blood is lost due to bleeding. A drop in the RBC count, hemoglobin and hematocrit can result in anemia, a condition in which tissues and organs in the body do not get enough oxygen, causing fatigue and weakness. If too many RBCs are produced, polycythemia results and the blood can become thickened, causing sluggish blood flow and related problems .
Notable variations by demographic group
- Males tend to have higher concentrations of red blood cells, higher haemoglobin and haematocrit, and there are separate reference ranges for males and females.
- In pregnancy, there is an increase in plasma volume of the blood in order to help supply oxygen and nutrients to mother and baby and therefore Women who are pregnant commonly have lower results for red cell count, hemoglobin and haematocrit.