The hematocrit test (HCT) measures the number of red blood cells (erythrocytes) in relation to white blood cells and platelets. Also known as a packed cell volume (PCV) test, the HCT is a simple blood test that is usually done in conjunction with other tests to help healthcare providers determine if you have a blood or marrow disorder. bone, nutritional deficiency or other condition. Often times, a hemoglobin (Hgb) test is done with an HCT blood test (critical for short); A pair of tests is called the H and H test.
What is the hematocrit?
Hematocrit is the percentage of volume of red blood cells (erythrocytes) in your blood. Measuring this percentage shows whether you have too many or too few red blood cells, which can be used to diagnose certain diseases.
The purpose of the test
By determining what percentage of your blood is red blood cells, an HCT test can be an early indicator of whether you have a condition that involves too many or too low of red blood cells.
This test is typically used by healthcare providers to detect anemia , a blood disorder associated with a low red blood cell count that causes fatigue, headaches, and dizziness. The test can also be used to detect polycythemia vera (PV), a rare blood disorder that enlarges the spleen and also causes fatigue and headaches.
If you are undergoing cancer treatment, HCT will be one of several standard tests that will be used to check your response to medications and for healthcare providers to monitor for side effects.
As a basic blood test , the HCT does not require fasting or special considerations. Blood is drawn from the elbow or the back of the hand. In infants and young children, the phlebotomist may make a small prick in the heel or fingertip and collect blood on a test strip.
An HCT test is usually prescribed as part of a complete blood count (CBC) test that performs multiple tests at the same time, so you may need to draw more than one vial of blood.
In addition to a complete blood count, other tests may be done at the same time or as a follow-up to help with the diagnosis, including:
- Blood smear : A small sample of blood is examined under a microscope to look for problems.
- Reticulocyte count : A blood test that measures how well the bone marrow makes red blood cells.
- Iron test: A group of blood tests, taken together, to check for iron deficiency or iron overload.
- Vitamin B12 and folate levels – a test to see if you have enough nutrients to make blood cells.
How is blood tested?
After blood is drawn, it is placed in a centrifuge or automated hematology analyzer. The centrifuge separates the red blood cells (red blood cells) from the white blood cells and platelets, allowing you to directly measure the percentage of red blood cells in the blood sample.
An automatic device that calculates the average volume of red blood cells, instead of a direct measurement, gives fast results, but can give false positive results. Depending on the purpose of the test, your healthcare professional will determine which method is best.
interpretation of results
Many factors affect hematocrit levels, but general guidelines for normal levels in adults and young children are as follows :
- Newborns (0 to 3 days) : 45% to 67%
- Newborns (3 days to 1 week) : 42% to 66%
- Infants (1 to 2 weeks) : 39% to 63%
- Babies (2 weeks to 1 month) : 31% to 55%
- Infants (1 to 2 months) : 28% to 42%
- Babies (2 months to 6 months) : 29% to 41%
- Infants (6 months to 2 years) : 33% to 39%
- Children (2-6 years) : 34% to 40%
- Children (6 to 12 years) : 35% to 45%
- Women (12 to adult) : 36% to 46%
- Men (12-18 years) : 37% to 49%
- Men (18 years to adult) : 41% to 53%
If your level is below or above normal, you may be at risk for one of these serious diseases.
|Hematocrit levels outside the normal range|
| Below normal
too few red blood cells cause anemia,
which can be caused by:
| Above normal
too many red blood cells that
can be caused by:
|Loss of blood due to internal or external trauma.||Heart disease|
|Leukemia, lymphoma, or other types of bone marrow cancer||Dehydration|
|Iron or vitamin deficiency, including folate, B12, or B6.||
Scars / thickening of the lungs
|Too much water in the body||
PV / other bone marrow disease
Obstructive sleep apnea
|Bone marrow damage from chemotherapy or toxins||
Carbon monoxide poisoning
|An autoimmune disorder like Evans syndrome.||
Increase in testosterone levels.
Other factors, such as a recent blood transfusion, pregnancy, or high altitude, can affect the results of your HCT test .
Your healthcare provider should discuss the results of your HCT and any other tests performed with you. If the results show that you are anemic, there are some simple steps you can take to improve your red blood cell count by strengthening your diet or using an over-the-counter iron supplement. If the anemia is the result of an infection, you may need to start taking antibiotics.
When the test results indicate a problem with the bone marrow , a bone marrow exam, in which a sample of bone marrow is taken, usually from the hip, may be needed to check for lymphoma and similar conditions.
Conditions associated with overproduction of red blood cells may require lifestyle changes, such as quitting smoking or switching to a heart-healthy diet . In rare cases, PV healthcare professionals can provide medications to help you cope with this condition, but it cannot be cured.
As long as your level is outside the normal hematocrit range, your healthcare provider will most likely repeat the HCT test at least once a year to check your condition.
Get the word of drug information
Nobody likes to get poked with a needle. However, the HCT test is one of those "worth it" tests. It's quick and easy, and it helps healthcare providers better understand your overall health. Everyday problems, such as fatigue or headaches, can be caused by simple anemia or by a more serious blood disorder that requires immediate attention. Either way, a simple blood test can make a big difference.