Increased hematocrit in the blood, causes and symptoms

The hematocrit is an important value in the blood test, which indicates the volume fraction of red blood cells (erythrocytes) in the circulating blood.

This value is considered part of the complete blood count.

The plasma (i.e. the blood without erythrocytes) has a low viscosity, about 1.3 centipois.

The blood viscosity has 3-4 centipoise.

The difference between the two is due to the presence of red blood cells.

With increased hematocrit, blood resistance increases (Poiseuille’s law). This means that the heart must work harder to maintain a sufficient speed of blood circulation.


Normal values of haematocrit

Normal hematocrit levels depend on the person’s age and gender (male or female).

Normal values are:

  • Newborns: 55% to 68%
  • Infants aged 1 week: 47-65%
  • Infants aged 1 month: 37-49%
  • Children aged 3 months: 30-36%
  • Children with 1 year: 29-41 %
  • Children with 10 years: 36-40 %
  • Adult men: 42-54%
  • Adult women: 38-46%


Men have a higher hematocrit because they have more testosterone than women.

Causes of increased hematocrit


Dehydration reduces plasma levels in the blood.

Plasma is the liquid component of blood that contains red and white blood cells.

If the percentage of plasma decreases, there is an increased hematocrit level in the body.

Increased hematocrit is called relative if it arises as a result of the reduction in plasma volume.

In this case, it is necessary to drink a lot to restore the right level of hematocrit.

Polycythemia vera

This is a disease of the bone marrow, which is characterized by a high number of red blood cells.

The bone marrow is a tissue that is located inside the bones, serves to generate the blood cells (white and red blood cells, platelets) and increases the volume.

In polycythemia vera, the bone marrow does not function properly.

The result is an increased production of erythrocytes and increased hematocrit values above 55%.


This condition causes liquid stool, which leads to high fluid loss.

Diarrhea can reduce the volume of plasma water and increase the volume (percentage) of red blood cells and thus also hematocrit.


Among the causes of increased hematocrit is erythrocytosis, a disease similar to polycythemia vera, which leads to an increase in the number of red blood cells.

The cause is an abnormality in the stem cells of the bone marrow. However, they can be recognized due to secondary factors, such as chronic lung disease.


Sometimes tumor cells cause an increase in red blood cells because they synthesize erythropoietin, which is normally produced by the kidneys.

The high hematocrit may be caused by a clear cell tumor of the kidney, the seat of Epo production.

In this case, the hematocrit can also reach values above 55-60%.

The result is hyperviscosity of the blood, which can cause:

  1. Itch
  2. Tinnitus
  3. Headache
  4. confusion (up to coma),
  5. Blood clot formation.

Other (rare) tumors that can increase Epo production include:

  1. liver carcinoma,
  2. tumors of the posterior cranial fossa (which occur mainly in children),
  3. hemangioblastoma of the cerebellum,
  4. Adenomas
  5. Kidney cysts.

Lung problems

If the lungs are unable to absorb an adequate amount of oxygen, the kidneys respond by increasing the production of red blood cells.

Increasing the number of erythrocytes makes it possible to meet the needs of the body.

Too high hematocrit levels are often associated with chronic lung diseases such as chronic obstructive pulmonary disease (COPD), which lead to increasing destruction of the lung alveoli.

Addison’s disease

In this condition, the adrenal glands, which are located close to the kidneys, cannot produce enough hormones (aldosterone and cortisone).

These hormones play a fundamental role in regulating blood pressure.

Blood tests in Addison’s disease patients show very high hematocrit levels.

Congenital cyanotic heart defects

This congenital (existing from birth) condition involves several changes in the heart that has not developed properly.

Heart disease hinders blood circulation in the heart.

Patients with congenital cyanotic heart defect have low oxygen levels in the blood.

As a result, the body produces more red blood cells to improve oxygen levels.

This increased production of red blood cells can increase hematocrit above normal.


A severe burn can greatly reduce the presence of plasma, thereby increasing the number of red blood cells in the blood.

In blood tests, this manifests itself in the form of increased hematocrit levels.


Elevated hematocrit levels are also observed in smokers.

Tobacco smoke:

  1. Narrows blood vessels,
  2. Reduces oxygen transport to different areas of the body.

When trying to provide more oxygen, the body increases its production of red blood cells (oxygen carriers), thus the hematocrit also increases.


Staying at high altitude (in the mountains) can increase the hematocrit count.

At higher altitudes, the availability of oxygen is reduced compared to normal.

In such environments, the body increases its erythrocyte production to meet the demand for oxygen.

EPO doping

EPO is mainly used to treat anaemia (low red blood cells).

The use of this substance leads to an increase in performance in athletes.

Anyone who exercises and takes elevated EPO doses has:

  1. more erythrocytes,
  2. An increased hematocrit level.

The benefit or benefit of increased hematocrit is increased oxygen in the blood.

Symptoms of increased hematocrit

Symptoms of increased hematocrit depend on the condition that led to this disorder.

For example, with polycythemia vera, one can suffer from:

  • Fatigue
  • Headache
  • excessive sweating,
  • Vertigo
  • Fever
  • spots on the skin,
  • itching especially after the shower or bath,
  • Blue-purple or purple patches similar to bruises that can form on the skin even in random areas.
  • joint and muscle pain,
  • Shortness
  • weight loss (if the polycythemia is caused by kidney cancer),
  • Chronic cough.

Complications and risk of increased hematocrit

If the hematocrit level remains greatly increased, the blood is too thick and viscous. Humans have an increased risk of:

  1. blood clots (deep vein thrombosis),
  2. Heart disease
  3. Stroke.

These diseases can be fatal, especially if the person also suffers from hypertension (high blood pressure).

When the disease, which causes a high number of red blood cells, is cured, these effects diminish or disappear altogether.

Hematocrit levels and increased hemoglobin

Hemoglobin is a protein in red blood cells.

Hemoglobin levels indicate whether a person has anemia (i.e. a lack of red blood cells) or other disorders.

High hematocrit and hemoglobin levels are present when plasma is reduced or red blood cells increase.

Reasons for this can be:

  • Dengue hemorrhagic fever: It increases the risk of dengue shock syndrome caused by blood loss.
  • Polycythemia vera is a condition in which the bone marrow produces too many white blood cells, which can lead to increased hematocrit.
  • Some lung diseases (such as chronic obstructive bronchopneumopathy) cause symptoms such as hypoxia (lack of oxygen) and can lead to increased red blood cell production.
  • Sometimes severe dehydration can cause a decrease in plasma and thus lead to an increase in erythrocyte concentration.

What can be done to lower the system? Treatment for elevated hematocrit

Therapy of elevated hematocrit depends on:

  1. The cause,
  2. The values,
  3. The general state of health of the patient.

Most people do not take medicine and do not follow any therapy if the hematocrit is slightly above normal.

Some patients with severely elevated hematocrit as a result of a condition such as polycythemia rubra vera may need:

  1. bloodletting (blood sampling),
  2. Small doses of aspirin.

Natural remedies include a healthy diet to prevent diarrhea and drinking enough water to avoid dehydration.

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