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Hematocrit Test - An Overview

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A hematocrit test reveals the number of red blood cells in the circulating blood and helps diagnose anemia. The detailed article is mentioned below.

Medically reviewed by

Dr. Abdul Aziz Khan

Published At October 18, 2022
Reviewed AtFebruary 21, 2023


Anemia is when the blood lacks enough red blood cells to provide oxygen to the body's cells, tissues, and organs. Anemia can result from various causes, such as iron and nutrition deficiency.

A hematocrit test result can help locate the cause of increased or decreased red blood cells. It could be due to a blood or bone marrow (where red blood cells are generated) disorder, nutritional deficiency, or any genetic condition. A hematocrit (HCT), also known as the packed-cell volume (PCV) test, is a simple blood test usually performed with other regular blood tests.

What Is a Hematocrit Test?

Hematocrit is a simple blood test to correctly measure the proportion of red blood cells in circulating blood by taking a blood sample. Red blood cells (erythrocytes) deliver oxygen throughout the body. An increased or decreased red blood cell count can indicate a medical condition or a developing disease.

Why Is a Hematocrit Test Needed?

  • Red blood cells (erythrocytes) are essential for distributing oxygen from the lungs to the body. The hematocrit test reveals the percentage of the blood that contains red blood cells and the thickness of the blood.

  • A shift in the HCT test can indicate the early onset of certain conditions. It can help diagnose certain diseases and capture responses to medication and treatment.

  • HCT test is a part of a complete blood count (CBC) in which multiple tests are run from a single withdrawal of blood. A CBC also evaluates white blood cells (part of the immune system) and platelets (critical in stopping bleeding and healing wounds).

  • Red blood cells contain a valuable protein called hemoglobin that binds oxygen so it can be delivered throughout the body. Often, a hemoglobin test is done along with an HCT blood test as part of a CBC. The HCT is mainly used to check for anemia (a blood disorder related to a low RBC count); tests will show a low hematocrit and hemoglobin.

  • The hematocrit test also checks for polycythemia vera (PV), a rare blood disease that increases the number of red blood cells and thickens the blood, showing high hematocrit. PV causes enlargement of the spleen causing fatigue and headaches.

  • Anemia can also be an adverse effect of cancer treatments, such as chemotherapy and radiation therapy. If you are undergoing cancer treatments, an HCT will be one of several routine tests to check how you respond to the medication.

Symptoms of anemia may include:

Symptoms of polycythemia may include:

  • Headaches, light-headedness or dizziness, shortness of breath, weakness, or fatigue.

  • Skin symptoms include itching, burning, or a red face after a shower or bath.

  • Heavy sweating, especially during sleep.

  • Blurred or double vision and blind spots.

  • Bleeding gums and heavy bleeding from minor cuts.

What Can Be Expected During a Hematocrit Test?

  • The test will begin by withdrawing the blood. The blood is usually withdrawn on the inside of the arm. When the needle is inserted to withdraw blood, there is moderate pain. A bandage will then cover the area after the blood withdrawal.

  • The HCT does not require fasting or special considerations as a basic blood test. However, with infants and young children, it may involve a small puncture in the heel or fingertip to collect blood onto a test strip.

  • It will require more than one vial of blood if the complete blood count is advised with a hematocrit test.

  • In addition, other tests are advised at the same time or as a follow-up to help with a diagnosis, including-

    • Blood Smear: A small blood sample is examined under a microscope using a dye.

    • Reticulocyte Count: A blood test determining how well the bone marrow (the spongy tissue inside bones) makes RBCs.

    • Iron Studies: A group of blood tests is interpreted together to check for iron deficiency or overload.

    • Vitamin B12 and Folate Levels: A test to see if there is a deficiency of nutrients such as vitamin B12 to create blood cells.

  • Once the blood is withdrawn, it is placed in a centrifugation machine using a vial or a container marked with a name. The centrifuge separates all the constituents of the blood (the red blood cells from the plasma (non-cellular liquid), white blood cells, and platelets).

Are There Risks to a Hematocrit Test?

Hematocrit is safe and a standard test. However, there is a slight risk in all kinds of trials.

  • Feeling faint, people who come for a blood test on an empty stomach or light snack.

  • Excessive bleeding is seen in people who are on blood-thinning medication.

  • A hematoma formation could be seen due to multiple punctures in the same region.

  • Infection is seen with ignorance during and after the blood collection.

What Are Normal Hematocrit Test Results?

Many factors affect hematocrit level; the range for normal tests varies due to age and gender; the general guidelines are

  • Male: 41 to 50%.

  • Female: 36 to 44%.

For babies, normal results are:

  • Newborn: 45 to 61%.

  • Infant: 32 to 42%.

The doctor or the healthcare professional will determine what is normal for the mother or her child.

  • If the levels are above or below average, one of these severe health issues could be the reason why HCT test results may be affected by factors such as:

  • Recent blood transfusion.

  • Pregnancy.

  • Living at a high altitude. Living at high altitudes with less oxygen in the air may cause an elevated hematocrit. That is because your body responds to low oxygen levels by making more red blood cells to get the oxygen you need.

  • The hematocrit test results are reported in numbers. The numbers represent the percentage of the blood made of red blood cells. So, for example, if the hematocrit test result is 42, 42 % of the blood is red blood cells, and the rest is white blood cells, platelets, and blood plasma.

What if the Hematocrit Result Is Outside the Normal Range?

Hematocrit results being low or high can indicate a severe medical condition. The healthcare provider can interpret the results and develop the best treatment plan for the underlying condition. The healthcare provider will consider a number of factors into account when interpreting the results.

A lower than average hematocrit can indicate:

  • Inadequate supply of healthy red blood cells (anemia). Different medical conditions can cause many types of anemia.

  • Your body is making too many white blood cells, which may be caused by:

    1. Bone marrow disease.

    2. Certain cancers include leukemia, lymphoma, multiple myeloma, long-term illness, or cancers that spread to the bone marrow from other body parts.

  • Vitamin or mineral deficiencies- iron and vitamin deficiency, including folate, vitamin B12, and vitamin B6.

  • Recent or long-term blood loss.

  • Significant water retention in the body.

  • Kidney disease.

  • Thyroid abnormality.

  • Immune destruction of red blood cells.

  • Leukemia or other bone marrow problems.

A higher than average hematocrit can indicate:

  • Dehydration.

  • Shock (blood plasma is deficient).

  • Polycythemia vera.

  • Lung or heart disease body is making too many red blood cells.

  • Scarring or thickening of the lungs.

  • Bone marrow disease.

  • Obstructive sleep apnea.

  • Smoking.

  • Carbon monoxide poisoning.

  • Testosterone use.

Pregnancy can cause a low hematocrit. That is because the body has more fluid than average during pregnancy, decreasing the percentage of red blood cells. To understand what your test results mean, talk with your provider.

Suppose your results and other tests indicate that you have iron-deficiency anemia. In these conditions, red blood cell count can be improved by fortifying your diet with iron-rich foods. A few examples of iron-rich foods include red meat, chicken, liver, eggs, shrimp, tuna, spinach, peas, broccoli, whole wheat bread, tofu, and beans.


A hematocrit test is a simple blood procedure that provides some important information about your health illnesses. It can be used to diagnose or monitor blood disorders, dehydration, nutrient deficiencies, blood-related cancers, and many other conditions. A hematocrit test may be repeated, or other blood tests may be recommended if the outcomes are conflicting.

Frequently Asked Questions


What Does It Mean When the Hematocrit Is Low?

When the hematocrit is low, it means that the person has less red blood cells. This can be indicative of anemia (a condition where the body lacks sufficient red blood cells). On the other hand, when the hematocrit is high, the person has more red blood cells than required. It can be indicative of polycythemia (abnormal increase in red blood cells) or erythrocytosis (another name for polycythemia).


What Is Hematocrit?

The percentage of red blood cells in the blood is called hematocrit. In men, normal levels of hematocrit can be 41 % to 50 %. On the other hand, in women, it can be 36 % to 48 %. However, it can be different depending on age. Pregnant women also may have different values.


Is High Hematocrit Dangerous?

It is considered high when the hematocrit is above 50 % in men and more than 46 % in women. When hematocrit is high, there are more red blood cells than required. It means that the body produces too many red blood cells than usual. It can be seen in lung diseases, congenital heart diseases, etc.


What Are the Causes for an Increase in Hematocrit?

A low hematocrit can be increased by mild modifications in the diet. Consumption of red meat, shellfish, oysters, and dried fruits like apricots and prunes can help to increase hematocrit. Liver, green leafy vegetables, beans, cereals, etc also help to increase hematocrit. Food rich in iron helps in the formation of red blood cells.


How Can Hematocrit Be Reduced?

Hematocrit can be reduced by making changes in lifestyle and diet. Staying hydrated will reduce hematocrit. Reducing iron intake, avoiding smoking and alcohol intake, etc, helps to reduce hematocrit. Increasing bran consumption will also help to reduce hematocrit.


What Are the Normal Levels of Hematocrit?

A healthy adult male should have hematocrit 41 to 50 %. A healthy woman should have it around 36 to 44 %. Infants should have a normal value between 32 to 40 %. Hematocrit in a newborn can be 45 to 65 %.


Does Vitamin D Influence Hematocrit?

Yes, studies have shown that taking Vitamin D supplements can increase hematocrit. This is because Vitamin D stimulates erythropoiesis. It is a process by which red blood cells are produced. It also increases the hemoglobin levels in the blood.


What Are Dangerously Low Levels of Hematocrit?

When hematocrit is less than 35 % in women and less than 40 % in men, it is considered dangerously low levels. It can indicate chronic anemia. Blood loss can also be associated with low hematocrit. It can mean that the person has fewer red blood cells than required.


Can Exercise Influence Hematocrit?

Yes, exercise can help to increase hematocrit. Changes in hematocrit occur rapidly during exercise. It increases hemoglobin levels and red blood cell count. It enhances oxygen-carrying capacity as well.


Is High Hematocrit and High BP Related?

Yes, elevated hematocrit can cause high blood pressure (BP). This is because the viscosity of the blood is increased. Studies show that erythrocyte count will be elevated in hypertensive (increased blood pressure) patients. This puts an additional load on the cardiovascular system.


What Is Hematocrit Effect?

The hematocrit effect is seen when layering heavier cellular components of blood on a supernatant. It is usually seen in anticoagulation or coagulation therapy. It is observed in magnetic resonance imaging or computed tomography scans.


Does High Hematocrit and High Hemoglobin Have Any Relation?

Yes, people with high hematocrit will have high levels of hemoglobin. The viscosity of blood will be higher in these people. This is because their red blood cell count in the blood is high. As a result, their oxygen-carrying capacity will also be high.


What Levels of Hemoglobin Are Considered Dangerously High?

Hemoglobin levels of more than 16.6 g/dl of blood in men and 15 g/dL in women are considered dangerously high. However, the threshold for high hemoglobin can differ from person to person. When the hemoglobin levels are more than 20 gm/dl, it is considered a clinically alert situation. Obstruction of the capillaries leading to hemoconcentration (an increase in the concentration of plasma contents in the blood) can occur in such situations.


Can Turmeric Reduce the Hematocrit Value?

Studies show that curcumin can effectively reduce blood viscosity. This reduces the plasma viscosity. As a result, hematocrit is lowered. It can also reduce iron levels in the blood.
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Dr. Abdul Aziz Khan
Dr. Abdul Aziz Khan

Medical oncology


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