What does thick blood mean

Thick Blood »Causes, Symptoms, and Treatment

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“Thick” or more precisely thick blood is caused by the fact that the proportion of blood cells that cause the red color is higher than normal. This changes the flow properties of the blood, so that the heart has to do more work to pump the more viscous juice through the fine veins of the capillary networks.

If necessary, this can lead to heart attacks or strokes. In the blood count, the blood value hematocrit (Hct, Hct) stands for “thick” or “thin” blood.


Why is blood thick?

The blood value hematocrit

As a parameter for “thick” or “thin” blood, the doctor determines the so-called hematocrit in the large and small blood counts. This blood value reveals how high the proportion of blood cells is in the total blood volume.

Since the red blood cells, along with the white blood cells (leukocytes) and blood platelets (thrombocytes), make up more than 99% of the blood cells, the blood value of the hematocrit corresponds almost exactly to the volume of the erythrocytes in the blood volume. “Thick blood” is therefore synonymous with a high hematocrit value. For men, the reference range (the range within which the measured blood values ​​are considered normal and healthy) is between 40 and 54 percent, for women, due to their regular menstrual periods, it is somewhat lower, between 37 and 47 percent.

Thick blood and its causes

  1. Thick or viscous blood means that there are more solid parts in the form of blood cells in a certain volume of blood than would be normal.
  2. As a result, this is either due to too many blood cells or not enough blood plasma.
  3. Too many blood cells usually means too many red blood cells. This means that too much of these are formed in the bone marrow.
  4. Too little blood plasma means too little fluid. This happens when the fluid intake is too low due to drinking or the kidneys excrete too much urine and thus water due to pathological changes.
  5. Thick blood is considered a risk factor for blood clots to form, which can lead to heart attacks, strokes, and other diseases.

Thick blood, what does the hematocrit say too high or too low?

If the blood hematocrit value deviates from the reference range, this means that the ratio of solid to liquid blood components has shifted. Thin blood = low hematocrit is due to too few blood cells in too much volume. Thick blood is caused on the one hand by insufficient production or dissolution (hemolysis) of erythrocytes or by blood loss.

On the other hand, in increased fluid intake, for example through drinking, or reduced fluid excretion due to kidney diseases and diarrhea. Thick blood = high hematocrit means that too many red blood cells float in too little volume. Too high a proportion of erythrocytes is called polyglobulia, and a lack of fluid is called dehydration.

  • An increased production of red blood cells occurs with longer stays at altitude, as the body has to compensate for the reduced oxygen supply.
  • Doping with erythropoietin (EPO) causes the bone marrow to produce more erythrocytes.
  • Pathologically, the same thing happens with a disease of the bone marrow, the Polycythemia vera.
  • Too many erythrocytes to compensate for a reduced oxygen supply can be observed in chronic lung diseases such as chronic obstructive pulmonary disease (COPD).
  • Probably the most common reason for thick blood and high blood hematocrit levels is dehydration due to insufficient fluid intake. Older people in particular are becoming increasingly lazy to drink and consuming far too little fluids.
  • Diarrhea and kidney dysfunction also lead to excessive fluid loss and thick blood.

Thick blood and its causes: why is high hematocrit dangerous?

High blood values ​​for the hematocrit mean that the blood contains more solid than liquid components. This makes it thicker. This means hard work for the heart, because the thick blood has to be pumped through the entire body and through the fine capillary networks of the organs.

This manifests itself in heart problems like Angina pectoris and shortness of breath with the slightest exertion. Since the reduced blood flow and lack of oxygen are particularly evident in the brain, it can lead to headaches, nausea and dizziness.

The true color of blood

Blood as a life-sustaining element has always fascinated mankind. Its red as a symbolic color has established itself over the centuries. It has become an indispensable part of society and art. The term blood red is based on the color of blood when we look at it with the naked eyes outside the body. The question remains why the veins appear bluish through the skin.

Who is responsible for the color of the blood?

Blood consists of the following solid components:

• leukocytes (white blood cells),
• erythrocytes (red blood cells),
• Platelets (blood platelets).

The plasma gives the blood its liquid. It is viewed in isolation of a clear yellow color. White blood cells and platelets are only visible under the microscope. The red blood cells are responsible for the red color.

They contain the blood pigment hemoglobin, which we perceive as red with the human eye. Its task is the transport of oxygen to all body cells and the removal of carbon dioxide as a metabolic product via the lungs. Hemoglobin contains iron to bind oxygen. The lifespan of erythrocytes is between 100 and 140 days. Every month, 1.2 liters of new blood are formed in the body, using the iron from the old cells.

The blue color of the blood under the skin

The red color of blood appears bluish in the veins under the skin. This has to do with the refraction of light in the skin. The term “blue blood” used by the nobles comes from this phenomenon. The noble class had whiter skin than the rest of the population, as they did not expose themselves to the sun daily through hard work. Her skin was whiter and the shimmering blue veins were more visible.

The blood appears blue because of the skin and its layers that reflect the different waves of light. There is no difference in the case of small veins lying close to the surface of the skin, since we perceive them as red. They are the reason for the reddish color of the skin in situations of shame or embarrassment. The veins, which are less than half a millimeter under the skin, reflect the long-wave rays, which our eyes perceive as red.

The veins, which are deeper than two millimeters under the skin, absorb the red rays. They reflect the short-wave blue light. With an intense beam of light from a flashlight, all of the veins that are visible under the skin appear red. This is the true color of blood.

Red blood and its pitfalls

The blue and red blood story is not based on physical knowledge because the color of blood is the same in all people. Nevertheless, there are differences which in certain cases can be life-threatening in one's own family. Men who get a blood transfusion from their mother are more likely to die.

This is shown by a Dutch study by the scientist Rutger Midelburg from the Leiden University Medical Center. The group examined data from 31,000 patients with an average age of 65 who received a blood transfusion in a Dutch hospital between 2005 and 2019. [Source: Jimenéz, Fanny: The blood of mothers makes men more likely to die (October 18, 2019), URL: https://www.welt.de/gesundheit/article169774855/Das-Blut-von-Muettern-laesst-Maenner-eher -sterben.html (last accessed: 02/10/2019)].

Sources and literature:

  1. H. Löffler, J. Rastetter, T. Haferlach, L. Heilmeyer, H. Begemann: Clinical Hematology Atlas. 6th edition. Stuttgart 2012: Springer-Verlag. ISBN-10: 3642621406.
  2. Matthias Imöhl: Laboratory medicine pocket. 5th edition. Grünwald 2019: Börm Bruckmeier-Verlag. ISBN-10: 3898627772.
  3. Birgid Neumeister (editor), Ingo Besenthal (editor), Bernhard Otto Böhm (editor): Clinical guidelines for laboratory diagnostics: with access to the Elsevier portal paperback. Munich 2008: Elsevier / Urban & Fischer-Verlag. ISBN-10: 3437222325.
  4. Marlies Michl: BASICS hematology. 4th edition. Munich 2019: Elsevier / Urban & Fischer-Verlag. ISBN-10: 3437421697.
  5. Maria Lohmann: Understand laboratory values. Compact guide: blood, urine and stool analyzes - an overview of normal values ​​- technical terms and important abbreviations. 4th edition. Murnau 2019: Mankau-Verlag. ISBN-10: 3863741587.

Doctor of medical science and natural scientist with a medical doctorate. This article conforms to current scientific standards and medical guidelines. (Authors M.Foerster / H.Stephan)