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Causes of hemoglobin increase and decrease
Last reviewed: 06.07.2025

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The concentration of hemoglobin in the blood may increase (up to 180-220 g/l and higher) in myeloproliferative diseases (erythremia) and symptomatic erythrocytosis accompanying various conditions. A study of hemoglobin concentration in dynamics provides important information about the clinical course of the disease and the effectiveness of treatment. A false increase in the concentration of hemoglobin in the blood is observed in hypertriglyceridemia, leukocytosis above 25.0×10 9 /l, progressive liver diseases, the presence of hemoglobin C or S, myeloma disease or Waldenström's disease (the presence of easily precipitating globulins).
Diseases and conditions accompanied by changes in the concentration of hemoglobin in the blood
Increased hemoglobin concentration |
Decreased hemoglobin concentration |
Primary and secondary erythrocytosis Erythremia Dehydration Excessive physical exertion or excitement Long-term stay at high altitudes Smoking |
All types of anemia associated with:
Overhydration |
There are several types of hemoglobin in human blood: HbA1 (96-98%), HbA2 (2-3%), HbF (1-2%), differing in the amino acid composition of globin, physical properties and affinity for oxygen. In newborns, HbF predominates - 60-80%, by the 4th-5th month of life its amount decreases to 10%. HbA appears in a 12-week fetus, in an adult it makes up the bulk of hemoglobin. HbF in a concentration of up to 10% can be found in aplastic, megaloblastic anemia, leukemia; in major beta-thalassemia, it can make up 60-100% of the total hemoglobin, in minor - 2-5%. An increase in the HbA2 fraction is characteristic of beta-thalassemia (in major beta-thalassemia - 4-10%, in minor - 4-8%). An increase in the HbA2 content is observed in malaria, acute lead poisoning and chronic lead intoxication. However, in these conditions, a change in the ratio of hemoglobin fractions is not a defining symptom.
The appearance of pathological forms of hemoglobin is caused by a violation of the synthesis of globin chains (hemoglobinopathies). The most common hemoglobinopathy is S - sickle cell anemia. The main method for detecting pathological forms of hemoglobin is the electrophoresis method.
Methemoglobin is formed when hemoglobin is exposed to a number of substances that convert the divalent iron of hemoglobin into trivalent iron. Methemoglobin is not capable of reversibly bonding with oxygen and cannot transport oxygen. Substances that cause the formation of methemoglobin constantly enter the blood from the tissues and intestines, but the amount of methemoglobin in the blood of healthy people remains small - 0.4-1.5% of the total hemoglobin content.
Methemoglobinemia (methemoglobin content greater than 1.5% of the total hemoglobin content) may occur as a result of hereditary diseases or exposure to toxic agents. These may include various substances (potassium chlorate, benzene derivatives, aniline, nitrogen oxides, some synthetic dyes, methyl nitrophosphates, well water nitrates, etc.). Methemoglobinemia may develop with enterocolitis.
At low levels of methemoglobinemia (less than 20% of the total amount of hemoglobin), clinical and hematological symptoms may be absent. Severe methemoglobinemia causes a decrease in the oxygen capacity of the blood, developing with a sufficient or even compensatory increase in the amount of hemoglobin and erythrocytes. Pathological inclusions (Heinz bodies) may be found in the erythrocytes. Sometimes, slight reticulocytosis is possible.