Exploring the Connection Between Fever and Hemoglobin Levels

Fever and Hemoglobin Relationship

Hello, I would like to ask if there is a correlation between fever and hemoglobin levels.
When a person has a fever, does the proliferation of white blood cells cause a decrease in hemoglobin measurement? If so, how low can it go? Can it drop below 9? If this is not the case, are the only causes of decreased hemoglobin internal and external bleeding?

Xiao Huang, 20~29 year old female. Ask Date: 2013/12/16

Dr. He Dongjin reply Cardiology

Hello, fever does not affect hemoglobin measurement.
If hemoglobin levels are low, it should still be considered due to possible bleeding.
Further investigation is needed to check for any sources of bleeding.
Changhua Hospital cares about you.

Reply Date: 2013/12/16

More Info

The relationship between fever and hemoglobin levels is a complex one, influenced by various physiological and pathological factors. Fever, which is a common response to infection or inflammation, can lead to changes in the body’s hematological parameters, including white blood cell (WBC) counts and hemoglobin (Hb) levels.
When the body experiences a fever, it often triggers an immune response that can lead to leukocytosis, or an increase in white blood cells. This is a normal response as the body attempts to fight off infections. However, the increase in white blood cells does not directly cause a decrease in hemoglobin levels. Instead, hemoglobin levels can be influenced by several other factors during a febrile illness.

One potential reason for a decrease in hemoglobin levels during fever could be related to the underlying cause of the fever itself. For instance, conditions such as hemolytic anemia, where red blood cells are destroyed faster than they can be produced, can lead to both fever and low hemoglobin levels. Additionally, chronic infections or inflammatory diseases can lead to anemia of chronic disease, where the body’s iron metabolism is altered, resulting in lower hemoglobin levels despite normal or increased iron stores.

Regarding your specific question about whether hemoglobin levels can drop below 9 g/dL during a fever, it is indeed possible, especially if there is an underlying condition causing both the fever and the anemia. However, in a healthy individual without any significant underlying pathology, a mild fever alone is unlikely to cause such a drastic drop in hemoglobin levels. Typically, hemoglobin levels below 9 g/dL indicate a more serious condition, such as significant blood loss (either internal or external), severe hemolysis, or bone marrow suppression.

If hemoglobin levels are found to be low, it is essential to investigate the cause further. Common causes of anemia include:
1. Acute or Chronic Blood Loss: This can occur due to gastrointestinal bleeding, heavy menstrual periods, or trauma.

2. Nutritional Deficiencies: Deficiencies in iron, vitamin B12, or folate can lead to anemia.

3. Bone Marrow Disorders: Conditions affecting the bone marrow, such as aplastic anemia or malignancies, can impair red blood cell production.

4. Chronic Diseases: Conditions like chronic kidney disease or inflammatory diseases can lead to anemia of chronic disease.

In summary, while fever itself does not directly cause a decrease in hemoglobin levels, the underlying causes of fever can lead to changes in hemoglobin. If you are experiencing persistent fever and low hemoglobin levels, it is crucial to seek medical evaluation to determine the underlying cause and appropriate treatment. Blood tests, including a complete blood count (CBC), reticulocyte count, and iron studies, can provide valuable information in diagnosing the issue.

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