Hematocrit (HCT)

The Hematocrit (HCT) test contains 1 test with 1 biomarker.

Description: The Hematocrit test is a blood test used to measure the percentage of red blood cells in your blood, usually for determining anemia.

Also Known As: HCT Test, Crit Test, Packed Cell Volume Test, PCV Test

Collection Method: Blood Draw

Specimen Type: Whole Blood

Test Preparation: No preparation required

When is a Hematocrit test ordered?

A full blood count usually includes a hematocrit measurement. It can also be ordered as part of a general health assessment, either by itself or in conjunction with a hemoglobin level. When a person develops signs and symptoms of a disorder that affects RBCs, such as anemia or polycythemia, these tests are frequently done.

When someone has signs and symptoms of severe dehydration, such as intense thirst, dry mouth or mucous membranes, and a lack of perspiration or urination, a hematocrit may be requested.

When someone has been identified with recurrent bleeding difficulties, anemia, or polycythemia, this test may be repeated numerous times or on a regular basis to check the success of treatment. It may also be ordered on a regular basis for persons receiving therapy for cancers that affect the bone marrow.

What does a Hematocrit blood test check for?

A hematocrit is a test that determines the percentage of red blood cells in a person’s blood. RBCs, white blood cells, and platelets are suspended in plasma, a fluid component of blood. The hematocrit is a ratio that compares the volume of red blood cells to the volume of all of these components together, which is known as whole blood. A percentage or fraction is used to express the value. A hematocrit of 40%, for example, indicates that there are 40 milliliters of red blood cells per 100 milliliters of blood.

The hematocrit is a quick and easy approach to assess a person’s red blood cells and screen for disorders like anemia. It’s frequently done in conjunction with a hemoglobin level, and it’s also a part of a complete blood count, which is commonly used to assess a person’s overall health.

RBCs are made in the bone marrow and discharged into the bloodstream when they are fully mature or almost so. They normally constitute about 37 to 49 percent of the blood volume. Hemoglobin, a protein that binds to oxygen, is found in RBCs. RBCs’ main job is to transport oxygen from the lungs to the body’s tissues and organs. They also transfer a little amount of carbon dioxide from tissues and organs back to the lungs, where it is exhaled.

RBCs have a 120-day lifespan, and the bone marrow must constantly manufacture new RBCs to replace those that have aged and degraded or have been lost due to hemorrhage. A variety of disorders can impact the bone marrow’s ability to produce new RBCs or the longevity of those already in circulation, as well as cause substantial bleeding.

The hematocrit measures both the number and volume of red blood cells. The hematocrit will drop when the size of the RBCs decreases, and vice versa. In general, the hematocrit will rise as the number of red blood cells increases, and it will fall to less than normal when the number of RBCs produced by the bone marrow decreases, the number of RBCs destroyed increases, or blood is lost due to hemorrhage. The overall amount of RBCs and hematocrit will diminish if the bone marrow is unable to manufacture new RBCs quickly enough, resulting in anemia.

Anemia is a condition in which the body is unable to provide adequate oxygen to tissues and organs, resulting in weariness and weakness. Too many RBCs are created in polycythemia, and the blood thickens, causing sluggish blood flow and other complications.

Lab tests often ordered with a Hematocrit test:

  • Hemoglobin
  • RBC Count
  • Blood Smear
  • Iron Total
  • Iron and Total Iron Binding Capacity
  • Ferritin
  • Reticulocyte Count
  • Vitamin B12
  • Folate
  • Complete Blood Count (CBC)
  • G6PD
  • Erythropoietin
  • Hemoglobinopathy Evaluation

Conditions where a Hematocrit test is recommended:

  • Anemia
  • Sickle Cell Anemia
  • Thalassemia
  • Myeloproliferative Neoplasms
  • Bone Marrow Disorders

How does my health care provider use a Hematocrit test?

The hematocrit test is frequently used to diagnose anemia, usually in conjunction with a hemoglobin test or as part of a full blood count. The test can be used to detect, diagnose, or track a variety of illnesses and disorders that impact the amount of red blood cells in the blood. RBCs are red blood cells that circulate in the blood and transport oxygen throughout the body.

Some circumstances influence RBC formation in the bone marrow, resulting in an increase or decrease in the number of mature RBCs discharged into circulation. The longevity of RBCs in the circulation may be affected by other factors. The overall number of RBCs and hematocrit will diminish if there is increased destruction or loss of RBCs, and/or the bone marrow is unable to make new ones quickly enough, leading in anemia.

The hematocrit can tell if there's a problem with RBCs, but it can't tell what's causing it. A blood smear, reticulocyte count, iron studies, vitamin B levels, and, in more severe cases, a bone marrow examination are some of the other tests that may be conducted at the same time or as follow-up to establish a reason.

What do my Hematocrit test results mean?

Red blood cells make up between 37 percent to 49 percent of the total amount of blood.

Because a hematocrit is frequently performed as part of a complete blood count, other components including RBC count, hemoglobin, reticulocyte count, and/or red blood cell indices are taken into account. Other considerations include age, gender, and race. In general, the hematocrit reflects the RBC count and hemoglobin readings.

Anemia is diagnosed by a low hematocrit, low RBC count, and low hemoglobin.

We advise having your results reviewed by a licensed medical healthcare professional for proper interpretation of your results.

The following is a list of what is included in the item above. Click the test(s) below to view what biomarkers are measured along with an explanation of what the biomarker is measuring.

Also known as: Crit, HCT, Hematocrit HCT, Packed cell volume, PCV


Hematocrit is a blood test that measures the percentage of the volume of whole blood that is made up of red blood cells. This measurement depends on the number of red blood cells and the size of red blood cells.
*Process times are an estimate and are not guaranteed. The lab may need additional time due to weather, holidays, confirmation/repeat testing, or equipment maintenance.

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