Hematocrit: High or Low? All You Need to Know

Polycythemia Vera Diagnosis | Leukemia and Lymphoma Society

Hematocrit: High or Low? All You Need to Know

While a person may have certain signs and symptoms of polycythemia vera (PV), laboratory tests are needed to confirm the diagnosis. Generally, a doctor will consider other conditions first.

Sometimes a condition called “secondary polycythemia” is causing the increase in red blood cells but, un PV, it does not begin in the bone marrow and is not a cancer. High red blood cell counts caused by secondary polycythemia are a reaction to another problem such as: 

  • High altitude
  • Disease that leads to low oxygenation of the blood
  • Kidney or liver tumor that secretes the hormone erythropoietin
  • Inherited disease

Secondary polycythemia is managed primarily by treating the underlying condition causing the disorder. A patient with secondary polycythemia should have a return to normal red blood cell counts once the primary problem is successfully treated.

Medical History and Physical Examination

Evaluation of an individual with suspected PV should start with a detailed medical history and a physical examination by a hematologist-oncologist

The medical history should include information about the patient’s:

  • Cardiovascular risk factors
  • Past illnesses
  • Injuries
  • Treatments
  • Medications
  • A history of the formation or presence of a blood clot inside a blood vessel (thrombosis) or loss of blood from damaged blood vessels (hemorrhagic events)
  • History of blood relatives—some illnesses run in families
  • Current symptoms

After the medical history, the doctor will conduct a physical examination. During the physical examination, the doctor may:

  • Listen to the patient's heart and lungs
  • Examine the patient's body for signs of disease
  • Check different organs of the body

Blood Tests

Complete Blood Count

This test measures the number of red blood cells, white blood cells and platelets in a sample of blood. It also measures the amount of the iron-rich protein that carries oxygen in red blood cells and the percent of whole blood made up of red blood cells (the hematocrit). People with PV have high red blood cell counts. They also often have:

  • Increased white blood cells and platelets
  • Increased hemoglobin levels
  • Increased hematocrit levels

Red Cell Mast Test

This procedure is used to measure the volume (amount) of red blood cells in relation to the volume of plasma (fluid) in whole blood.

In patients with PV, there may be an absolute increase in red blood cell mass.

This test is infrequently performed in the United States due to high cost, difficulty obtaining the appropriate test materials, and the advent of new blood tests such as mutational testing.

Peripheral Blood Smear

A procedure in which a blood sample is viewed under a microscope. A pathologist examines the sample to see if there are any unusual changes in the size, shape and appearance of various blood cells. The test also checks for the presence of immature (blast) cells in the blood. 

Comprehensive Metabolic Panel

These tests measure the levels of substances released into the blood by organs and tissues. These include electrolyes, fats, proteins, glucose (sugar) and enzymes.

Blood chemistry tests provide important information about how well a person’s kidneys, liver and other organs are working. For patients suspected of having PV, it is important to test the serum erythropoietin level.

Erythropoietin is a hormone naturally produced by the kidneys to stimulate the production of new red blood cells. Individuals with PV usually have very low levels of erythropoietin. 

Bone Marrow Tests

Your doctor may examine your bone marrow even though the test isn't needed to diagnose PV.

Bone marrow testing involves two steps usually performed at the same time in a doctor's office or a hospital:

  • A bone marrow aspiration to remove a liquid marrow sample
  • A bone marrow biopsy to remove a small amount of bone filled with marrow

In PV, the bone marrow shows above-normal numbers of blood cells and an abnormal number of the platelet-forming cells called “megakaryocytes” in the bone marrow. The pathologist also examines the chromosomes of the bone marrow cells to rule out other blood diseases. 

Molecular Testing

Molecular genetic tests are very sensitive tests that look for specific gene mutations. If PV is suspected, molecular testing for the JAK2 mutation should be performed. The JAK2 V617F mutation is found in more than 90 percent of PV patients.

The U.S. Food and Drug Administration (FDA) has approved a test called ipsogen JAK2 RGQ PCR Kit to detect mutations affecting the Janus Tyrosine Kinase 2 (JAK2) gene. This test is intended to help doctors evaluate patients for suspected PV.

For more information about bone marrow tests and other lab tests, please see the free LLS publication Understanding Lab and Imaging Tests.

Criteria for Diagnosing Polycythemia Vera

In 2016, the World Health Organization published new criteria for diagnosing PV. The diagnosis of PV requires the presence of

  • Major Criteria 1, 2, and 3 (listed below) or
  • Major Criteria 1 and 2 and the minor criterion(listed below) 

Major Criteria 1.  Very high red blood cell count, usually identified by either A, B, or C below:

  • A. Hemoglobin level
    • Elevated levels of hemoglobin
      • Hemoglobin levels greater than 16.5 g/dL in men
      • Hemoglobin levels greater than 16.0 g/dL in women
  • B. Hematocrit level
    • Elevated levels of hematocrit
      • Hematocrit greater than 49 percent in men
      • Hematocrit greater than 48 percent in women
  • C. Red cell mass

Major Criteria 2. Bone marrow biopsy (A or B below) showing:

  • A. An abnormal excess of blood cells in the bone marrow (called “hyercellularity”) with an elevation of red blood cells, white blood cells and platelets (called “panmyelosis”)
  • B. Proliferation of mature megakaryocytes that vary in size and shape

Major Criteria 3. Presence of the JAK2V617F or JAK2 exon 12 gene mutation

Minor Criterion: Very low levels of erythropoietin

Source: https://www.lls.org/myeloproliferative-neoplasms/polycythemia-vera/diagnosis

Hematocrit Test: MedlinePlus Lab Test Information

Hematocrit: High or Low? All You Need to Know
URL of this page: https://medlineplus.gov/lab-tests/hematocrit-test/

A hematocrit test is a type of blood test. Your blood is made up of red blood cells, white blood cells, and platelets. These cells and platelets are suspended in a liquid called plasma.

A hematocrit test measures how much of your blood is made up of red blood cells. Red blood cells contain a protein called hemoglobin that carries oxygen from your lungs to the rest of your body.

Hematocrit levels that are too high or too low can indicate a blood disorder, dehydration, or other medical conditions.

Other names: HCT, packed cell volume, PCV, Crit; Packed Cell Volume, PCV; H and H (Hemoglobin and Hematocrit)

A hematocrit test is often part of a complete blood count (CBC), a routine test that measures different components of your blood. The test is also used to help diagnose blood disorders such as anemia, a condition in which your blood doesn't have enough red cells, or polycythemia vera, a rare disorder in which your blood has too many red cells.

Your health care provider may have ordered a hematocrit test as part of your regular checkup or if you have symptoms of a red blood cell disorder, such as anemia or polycythemia vera. These include:

Symptoms of anemia:

Symptoms of polycythemia vera:

  • Blurred or double vision
  • Shortness of breath
  • Headache
  • Itching
  • Flushed skin
  • Tiredness
  • Excessive sweating

A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.

You don't need any special preparations for a hematocrit test. If your health care provider has ordered more tests on your blood sample, you may need to fast (not eat or drink) for several hours before the test. Your health care provider will let you know if there are any special instructions to follow.

There is very little risk to having a hematocrit test or other type of blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.

If test results show your hematocrit levels are too low, it may indicate:

If test results show your hematocrit levels are too high, it may indicate:

  • Dehydration, the most common cause of high hematocrit levels. Drinking more fluids will usually bring your levels back to normal.
  • Lung disease
  • Congenital heart disease
  • Polycythemia vera

If your results are not in the normal range, it doesn't necessarily mean that you have a medical condition requiring treatment. To learn more about your results, talk to your health care provider.

Many factors can affect your hematocrit levels, including a recent blood transfusion, pregnancy, or living at a high altitude.

  1. American Society of Hematology [Internet]. Washington D.C.: American Society of Hematology; c2017. Blood Basics; [cited 2017 Feb 20]; [about 2 screens]. Available from: http://www.hematology.org/Patients/Basics/
  2. Hinkle J, Cheever K. Brunner & Suddarth's Handbook of Laboratory and Diagnostic Tests. 2nd Ed, Kindle. Philadelphia: Wolters Kluwer Health, Lippincott Williams & Wilkins; c2014. Hematocrit; p. 320–21.
  3. Mayo Clinic [Internet]. Mayo Foundation for Medical Education and Research; c1998–2017. Hematocrit Test: Overview; 2016 May 26 [cited 2017 Feb 20]; [about 2 screens]. Available from: http://www.mayoclinic.org/tests-procedures/hematocrit/home/ovc-20205459
  4. Lab Tests Online [Internet]. Washington D.C.: American Association for Clinical Chemistry; c2001–2017. Hematocrit: The Test; [updated 2015 Oct 29; cited 2017 Feb 20]; [about 4 screens]. Available from: https://labtestsonline.org/understanding/analytes/hematocrit/tab/test/
  5. Lab Tests Online [Internet]. Washington D.C.: American Association for Clinical Chemistry; c2001–2017. Hematocrit: The Test Sample; [updated 2016 Oct 29; cited 2017 Feb 20]; [about 3 screens]. Available from: https://labtestsonline.org/understanding/analytes/hematocrit/tab/sample/
  6. Lab Tests Online [Internet]. Washington D.C.: American Association for Clinical Chemistry; c2001–2017. Hematocrit: At a Glance; [updated 2015 Oct 29; cited 2017 Feb 20]; [about 2 screens]. Available from: https://labtestsonline.org/understanding/analytes/hematocrit/tab/glance/
  7. National Cancer Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; NCI Dictionary of Cancer Terms: hematocrit; [cited 2017 Feb 20]; [about 3 screens]. Available from: https://www.cancer.gov/publications/dictionaries/cancer-terms?cdrid=729984
  8. National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Types of Blood Tests; [updated 2012 Jan 6; cited 2017 Feb 20]; [about 5 screens]. Available from: https://www.nhlbi.nih.gov/health-topics/blood-tests#Types
  9. National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; What Are the Risks of Blood Tests?; [updated 2012 Jan 6; cited 2017 Feb 20]; [about 7 screens]. Available from: https://www.nhlbi.nih.gov/health-topics/blood-tests#Risk-Factors
  10. National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; What Are the Signs and Symptoms of Anemia?; [updated 2012 May 18; cited 2017 Feb 20]; [about 8 screens]. Available from: https://www.nhlbi.nih.gov/health-topics/anemia#Signs,-Symptoms,-and-Complications
  11. National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; What Is Polycythemia Vera?; [updated 2011 Mar 1; cited 2017 Feb 20]; [about 3 screens]. Available from: https://www.nhlbi.nih.gov/health-topics/polycythemia-vera
  12. National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; What To Expect with Blood Tests; [updated 2012 Jan 6; cited 2017 Feb 20]; [about 6 screens]. Available from: https://www.nhlbi.nih.gov/health/health-topics/topics/bdt/with
  13. University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; c2017. Health Encyclopedia: Hematocrit; [cited 2017 Feb 20]; [about 2 screens]. Available from: https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=167&contentid;=hematocrit

Source: https://medlineplus.gov/lab-tests/hematocrit-test/

Hemoglobin and Hematocrit

Hematocrit: High or Low? All You Need to Know

Hemoglobin (Hb) is the protein contained in red blood cells that is responsible for delivery of oxygen to the tissues. To ensure adequate tissue oxygenation, a sufficient hemoglobin level must be maintained.

The amount of hemoglobin in whole blood is expressed in grams per deciliter (g/dl). The normal Hb level for males is 14 to 18 g/dl; that for females is 12 to 16 g/dl. When the hemoglobin level is low, the patient has anemia.

An erythrocytosis is the consequence of too many red cells; this results in hemoglobin levels above normal.

The hematocrit measures the volume of red blood cells compared to the total blood volume (red blood cells and plasma). The normal hematocrit for men is 40 to 54%; for women it is 36 to 48%.

This value can be determined directly by microhematocrit centrifugation or calculated indirectly. Automated cell counters calculate the hematocrit by multiplying the red cell number (in millions/mm3) by the mean cell volume (MCV, in femtoliters).

When so assayed, it is subject to the vagaries inherent in obtaining an accurate measurement of the MCV (see Chapter 152).

Both the hemoglobin and the hematocrit are whole blood and are therefore dependent on plasma volume.

If a patient is severely dehydrated, the hemoglobin and hematocrit will appear higher than if the patient were normovolemic; if the patient is fluid overloaded, they will be lower than their actual level.

To assess true red cell mass, independent radionuclide evaluation of the red cells and plasma (by 51Cr and 131I respectively) must be performed.

If the hematocrit must be determined quickly, as is often the case when a patient hemorrhages, it may be necessary to measure the hematocrit directly without the use of an automated counter. The materials needed are:

  • Lancets
  • Alcohol prep pads
  • Gauze pads
  • Microhematocrit tubes (heparinized)
  • Sealant (“Seal-Ease,” “Crit-Seal,” etc)
  • Microhematocrit centrifuge
  • Microhematocrit reader
  • If venipuncture is required: tourniquet, syringe, tube containing anticoagulant (EDTA, citrate)

For hematocrits obtained by fingerstick, wipe the fingertip pad of the fourth finger of the nondominant hand with the alcohol prep pad. Make certain the area is allowed to dry. Prick the fingertip with the lancet.

Place the hematocrit tube near the incision site and allow the blood to flow via capillary action into the hematocrit tube until it is two-thirds to three-fourths full or to a predesignated mark on the tube.

Avoid “milking” the finger if possible; this causes the expression of tissue fluids and may result in a falsely low hematocrit. Always fill at least three tubes. For hematocrits obtained by venipuncture, draw a sample of blood into the tube containing anticoagulant and mix well.

Dip the hematocrit tube into the blood and allow the blood to rise to the desired two-thirds to three-quarters level. Because blood cells naturally sediment, a prior thorough mixing of the blood in the tube is necessary to ensure accurate reading.

After cleaning the outside of the hematocrit tubes of excess blood, invert the tube slowly so that the blood migrates just short of the bottom end of the tube. Seal the bottom of the tube with sealant. Make certain that little or no air is interspersed in the column of blood. If the seal is incomplete, leakage will occur during centrifugation and false readings will be obtained.

Place the tubes in a microhematocrit centrifuge and spin for 3 to 5 minutes at high speed. A shorter spin will not allow for complete sedimentation.

Using either a hematocrit reader or any ruled apparatus, measure the length of the column of the packed red cells and divide it by the length of the whole column of blood (cells and plasma), as in Figure 151.1. To obtain the hematocrit, multiply this number by 100%. Average all readings obtained from the different microhematocrit tubes.

Example: If the column of packed red cells measures 20 mm and the whole blood column measures 50 mm, the hematocrit is 20/50 = 0.4 or (0.4 × 100%) = 40%.

Hemoglobin determinations will usually be performed by an automated cell counter from a tube of well-mixed EDTA-anticoagulated blood filled to a predetermined level.

In this assay, all forms of hemoglobins are converted to the colored protein cyanomethemoglobin and measured by a colorimeter. An inadequate sample, whether due to insufficient volume or inadequate anticoagulation, may give false readings.

If it is necessary to determine the level of anemia quickly, the hematocrit is an easier, more convenient test.

Hemoglobin electrophoresis measures the mobility of hemoglobin in an electric field; it can therefore detect only those abnormalities in hemoglobin that alter the charge. Electrophoretic mobilities are affected by pH and by the medium in which the test is conducted.

Screening tests typically use a hemolysate of anticoagulated blood electrophoresed on cellulose acetate at pH 8.6 to 8.8. If necessary, a further electrophoresis in starch gel at pH 6.2 to 6.8 is performed.

At that stage, the work will usually be performed by a specialized laboratory.

Hemoglobin electrophoresis will not readily assess situations where there are neutral amino acid substitutions or where the hemoglobin is normal but the constituent chains are not produced in equal numbers (thalassemias). The diagnosis of alpha thalassemia of a mild to moderate degree cannot be made by hemoglobin electrophoresis; the diagnosis of beta thalassemia may be made by inference from an increase in the Hb A2.

A standard electrophoresis would look Figure 151.2.

The molecular weight of hemoglobin is approximately 64,500 daltons. Hb is composed of two pairs of dissimilar chains, α and β, each defined by a specific amino acid sequence and incorporating an iron-containing heme group. Two α–β dimers combine to form a hemoglobin tetramer.

This allows for the “heme–heme” interaction necessary for effective oxygen uptake (deoxyhemoglobin → oxyhemoglobin) and delivery (oxyhemoglobin → deoxyhemoglobin). The oxygen affinity of hemoglobin is a function of this heme–heme interaction and of pH (Bohr effect), and is a measure of how many hemoglobin molecules have oxygen bound to them for a given level of oxygen tension.

In a normal individual the major hemoglobin is Hb A, constituting approximately 97% of the total hemoglobin. Variations and/or amino acid substitutions in these chains exist. Some are deleterious to the normal function of hemoglobin, whereas others may have relatively normal oxygen affinity and stability.

Hemoglobins containing different types of chains make up the remainder of the hemoglobin content in red cells (α2δ2 = Hb A2 approximately 2%; α2γ2 = Hb F approximately 1%).

Substitutions in the normal hemoglobin amino acid sequence may result in hemoglobins that have different sub-unit interactions and varying affinities for oxygen.

For example, a substitution of the sixth amino acid on the beta chain causes Hb S, or sickle hemoglobin. Hb S has a lower oxygen affinity and surrenders its oxygen more readily.

Hb F, a normal minor hemoglobin constituent, has a higher oxygen affinity.

If the oxygen dissociation curve is abnormal, the body will adjust the hemoglobin level to ensure adequate oxygen distribution to the tissues.

Thus in a rare disease hemoglobin Hotel Dieu, the difficulty in extracting oxygen from a variant hemoglobin with increased oxygen affinity could result in a lack of oxygen for the tissues (tissue hypoxia) and a compensatory erythrocytosis.

The smaller fraction of oxygen released from the hemoglobin is thereby offset by the increased number of hemoglobin molecules. Similarly, in sickle cell anemia, the decreased oxygen affinity allows these patients more tissue oxygen at any given hemoglobin level.

Many anemias are detected by routine laboratory screening performed before the patient is symptomatic. When the patient does have symptoms from an abnormality in the hemoglobin level, the symptoms are often a nonspecific weakness or fatigue.

The only finding on physical examination may be pallor; additional changes in the nail beds (such as spooning), glossitis (red tongue), or hepatosplenomegaly (enlarged liver or spleen) may give a clue to the etiology of the anemia.

Symptoms are usually related to the level of hemoglobin, its abruptness of onset and its duration. A patient with pernicious anemia may feel well at the same level of hemoglobin that would cause severe weakness in a patient with acute gastrointestinal hemorrhage.

This is due to volume compensation by plasma and shifts in the oxygen dissociation curve which occur over time.

When first confronted with an abnormal hemoglobin or hematocrit level, the next step is to assess the red cell indices (see Chapter 152), peripheral smear (Chapter 155), and the reticulocyte count (Chapter 156) in light of the patient's history and physical examination.

References

Source: https://www.ncbi.nlm.nih.gov/books/NBK259/

Hematocrit (HCT)

Hematocrit: High or Low? All You Need to Know

Hematocrit is a blood test that measures how much of a person's blood is made up of red blood cells. This measurement depends on the number of and size of the red blood cells.

How to Prepare for the Test

No special preparation is necessary for this test.

How the Test will Feel

When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.

Why the Test is Performed

The hematocrit is almost always done as part of a complete blood count (CBC).

Your health care provider may recommend this test if you have signs of or are at risk for anemia. These include having:

  • Grumpiness or tiredness
  • Headaches
  • Problems concentrating
  • Poor nutrition
  • Heavy menstrual periods
  • Blood in your stools, or vomit (if you throw up)
  • Treatment for cancer
  • Leukemia or other problems in the bone marrow
  • Chronic medical problems, such as kidney disease or certain types of arthritis

Normal Results

Normal results vary, but in general they are:

  • Male: 40.7% to 50.3%
  • Female: 36.1% to 44.3%

For babies, normal results are:

  • Newborn: 45% to 61%
  • Infant: 32% to 42%

The examples above are common measurements for results of these tests. Normal value ranges vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your provider about the meaning of your specific test results.

What Abnormal Results Mean

Low hematocrit may be due to:

  • Anemia
  • Bleeding
  • Destruction of red blood cells
  • Leukemia
  • Malnutrition
  • Too little iron, folate, vitamin B12, and vitamin B6 in the diet
  • Too much water in the body

High hematocrit may be due to:

  • Congenital heart disease
  • Failure of the right side of the heart
  • Too little water in the body (dehydration)
  • Low levels of oxygen in the blood
  • Scarring or thickening of the lungs
  • Bone marrow disease that causes abnormal increase in red blood cells

Risks

There is little risk involved with having your blood taken.Veins and arteries vary in size from one person to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight but may include:

  • Excessive bleeding
  • Fainting or feeling lightheaded
  • Multiple punctures to locate veins
  • Hematoma (blood buildup under the skin)
  • Infection (a slight risk any time the skin is broken)

Hematocrit Blood Test: Normal, High, Low Ranges & Results

Hematocrit: High or Low? All You Need to Know

Picture of Red Blood Cells

The hematocrit blood test determines the percentage of red blood cells (RBC's) in the blood. Blood is composed mainly of red blood cells and white blood cells suspended in an almost clear fluid called serum.

The hematocrit test indicates the percentage of blood by volume that is composed of red blood cells. The condition called “anemia” results from having too few red blood cells. Anemia causes a variety of symptoms.

The hematocrit is a basic test that can tell a physician a lot about a person's health. 

How Is the Hematocrit Measured?

In most labs, the hematocrit is measured by a machine that automatically determines a variety of blood tests referred to as the blood count (CBC). The complete blood count is a numerical listing of the hematocrit, as well as the hemoglobin concentration, and the three blood cell lines produced by the bone marrow (the red blood cells, the white blood cells, and the platelets).

Another simple method is termed the spun hematocrit or “spun crit.” A small amount of blood (about 0.05 to 0.1ml) is placed in a thin capillary tube, the tube is sealed with wax or clay, and then placed in a centrifuge to be spun.

The red cells collect at the bottom and form a red column and are separated from the straw-colored serum column by a small area composed of white blood cells. The height of the total blood in the capillary tube (red cells, white cells and serum equals 100%).

The height of the red cell column divided by the height of the total fluid in the capillary tube equals the hematocrit (percentage of RBC's in the total blood volume). This test can be performed in a few minutes.

What Is a Normal Hematocrit?

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Normal values for the hematocrit test vary according to age, sex, pregnancy, altitude where people live, and even vary slightly between various testing methods. The following are reported ranges of normal hematocrit levels:

  • Newborns: 55%-68%
  • One (1) week of age: 47%-65%
  • One (1) month of age: 37%-49%
  • Three (3) months of age: 30%-36%
  • One (1) year of age: 29%-41%
  • Ten (10) years of age: 36%-40%
  • Adult males: 42%-54%
  • Adult women: 38%-46%
  • Adult pregnant women: about 30% – 34% lower limits and 46% upper limits
  • High Altitude residents: about 45% – 61% in males; 41% – 56% in females (These levels gradually average higher as the altitude where people live increases. This is a result of the increased demand for the oxygen-carrying capacity of red blood cells at higher altitudes where there is decreased oxygen concentration in the atmosphere.)

These values may vary from authorities in the field by as much as 7%. Consequently, it is best to have a doctor explain the significance of an individual's level of hematocrit if it is not normal.

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What Does a Low Hematocrit Mean?

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A low hematocrit means the percentage of red blood cells is below the lower limits of normal (see above) for that person's age, sex, or specific condition (for example, pregnancy or high-altitude living). Another term for low hematocrit is anemia. Causes of low hematocrit, or anemia, include:

What Does a High Hematocrit Mean?

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A high hematocrit means the percentage of red blood cells in a person's blood is above the upper limits of normal (see above) for that person's age, sex, or specific condition (for example, pregnancy or high altitude living). Causes of a high hematocrit include:

How Is a Low or High Hematocrit Treated?

The treatment of high or low hematocrit depends on the underlying cause(s), the hematocrit level, and the overall health status of the individual. Most people are not treated with medications or procedures if the hematocrit is only slightly above or below the normal levels.

Some patients with very low hematocrits may require intravenous iron, transfusions or medications to stimulate the production of red cells by the bone marrow.

Some patients with very high hematocrits due to diseases, such as polycythemia rubra vera, may require blood letting (blood removal).

The patient's doctor will decide when medication or procedures are necessary for each particular individual. In general, abnormal hematocrit values are monitored by doctors with routine blood testing.

Reviewed on 9/3/2019

References

Medically reviewed by John A. Daller, MD American Board of Surgery with subspecialty certification in surgical critical care REFERENCES: “PedNSS Health Indicators.” CDC.gov. FDA.gov. Blood Products Advisory Committee. Topic II: Iron Status in Blood Donors.

Nabili, Siamak N. MD, MPH. “Complete Blood Count (CBC).” MedicineNet.com. Updated Jan 24, 2014.

Shiel, William C. Jr., MD, FACP, FACR. “Hematocrit.” MedicineNet.com. Updated Oct. 19, 2015.

Source: https://www.emedicinehealth.com/hematocrit_blood_test/article_em.htm

Hematocrit

Hematocrit: High or Low? All You Need to Know

Hematocrit is a blood test that measures how much of a person's blood is made up of red blood cells. This measurement depends on the number of and size of the red blood cells.

Blood transports oxygen and nutrients to body tissues and returns waste and carbon dioxide. Blood distributes nearly everything that is carried from one area in the body to another place within the body.

For example, blood transports hormones from endocrine organs to their target organs and tissues. Blood helps maintain body temperature and normal pH levels in body tissues.

The protective functions of blood include clot formation and the prevention of infection.

A blood sample is needed.

No special preparation is necessary for this test.

When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.

The hematocrit is almost always done as part of a complete blood count (CBC).

Your health care provider may recommend this test if you have signs of or are at risk for anemia. These include having:

  • Grumpiness or tiredness
  • Headaches
  • Problems concentrating
  • Poor nutrition
  • Heavy menstrual periods
  • Blood in your stools, or vomit (if you throw up)
  • Treatment for cancer
  • Leukemia or other problems in the bone marrow
  • Chronic medical problems, such as kidney disease or certain types of arthritis

Normal results vary, but in general they are:

  • Male: 40.7% to 50.3%
  • Female: 36.1% to 44.3%

For babies, normal results are:

  • Newborn: 45% to 61%
  • Infant: 32% to 42%

The examples above are common measurements for results of these tests. Normal value ranges vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your provider about the meaning of your specific test results.

Low hematocrit may be due to:

  • Anemia
  • Bleeding
  • Destruction of red blood cells
  • Leukemia
  • Malnutrition
  • Too little iron, folate, vitamin B12, and vitamin B6 in the diet
  • Too much water in the body

High hematocrit may be due to:

  • Congenital heart disease
  • Failure of the right side of the heart
  • Too little water in the body (dehydration)
  • Low levels of oxygen in the blood
  • Scarring or thickening of the lungs
  • Bone marrow disease that causes abnormal increase in red blood cells

There is little risk involved with having your blood taken.Veins and arteries vary in size from one person to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight but may include:

  • Excessive bleeding
  • Fainting or feeling lightheaded
  • Multiple punctures to locate veins
  • Hematoma (blood buildup under the skin)
  • Infection (a slight risk any time the skin is broken)

Chernecky CC, Berger BJ. H. Hematocrit (Hct) – blood. In: Chernecky CC, Berger BJ, eds. Laboratory Tests and Diagnostic Procedures. 6th ed. St Louis, MO: Elsevier Saunders; 2013:620-621.

Maheshwari A, Carlo WA. Blood disorders. In: Kliegman RM, Stanton BF, St. Geme JW, Schor NF, eds. Nelson Textbook of Pediatrics. 20th ed. Philadelphia, PA: Elsevier; 2016:chap 103.

Vajpayee N, Graham SS, Bem S. Basic examination of blood and bone marrow. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 23rd ed. St Louis, MO: Elsevier; 2017:chap 30.

Last reviewed on: 2/18/2018

Reviewed by: Laura J. Martin, MD, MPH, ABIM Board Certified in Internal Medicine and Hospice and Palliative Medicine, Atlanta, GA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

Source: https://www.mountsinai.org/health-library/tests/hematocrit

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