What Causes High Red Blood Cell Count? More Than Just Dehydration
Introduction
If a blood test reveals your red blood cell (RBC) count to be high, the usual assumption is dehydration. Although dehydration is a likely cause, it is frequently only the beginning of things. High RBC levels may reflect a myriad of underlying conditions — some benign, some life-threatening. This article explores what actually produces elevated red blood cell counts and why dehydration is merely a part of the problem.
1. Red Blood Cells and Their Function
Red blood cells are the most common form of blood cell in the human body. Their main function is to transport oxygen from the lungs to tissues throughout the body and bring carbon dioxide back to the lungs to be exhaled. RBCs have a protein inside called hemoglobin, which grabs onto oxygen molecules.
Normal Values:
RBC Count:
Men: 4.7 to 6.1 million cells per microliter (mcL)
Women: 4.2 to 5.4 million cells/mcL
Hemoglobin:
Men: 13.8 to 17.2 grams per deciliter (g/dL)
Women: 12.1 to 15.1 g/dL
Hematocrit (percentage of blood volume occupied by RBCs):
Men: 40.7% to 50.3%
Women: 36.1% to 44.3%
A "high" count for RBCs indicates values above these normal ranges.
2. Dehydration: A Common but Misleading Culprit
Dehydration decreases the liquid (plasma) component of the blood, making red cells seem more concentrated — a condition called relative polycythemia.
How it works:
-Plasma volume decreases, but red cell mass does not change.
-The RBC level, hemoglobin, and hematocrit look higher.
-This is reversible and tends to resolve with hydration.
Causes of dehydration that are common:
-Vomiting, diarrhea
-Excessive sweating
-Fever
-Diuretic drugs
-Inadequate fluid administration
Although this kind of increase does not indicate an actual increase in the production of red blood cells, it does deserve consideration, particularly if the level fails to normalize after rehydration.
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3. True (Absolute) Polycythemia: When the Body Overproduces Too Many RBCs
When increased red blood cells don't get better even after dehydration is corrected, then the underlying cause could be absolute polycythemia, where there is actually more production of RBCs.
Absolute polycythemia is classified into:
Primary causes: Disorders of the bone marrow
Secondary causes: External conditions such as low oxygen, tumors, etc.
4. Primary Polycythemia: When the Bone Marrow Becomes Rogue
A. Polycythemia Vera (PV)
Cause: A rare blood cancer in which the bone marrow overproduces too many RBCs — and, on occasion, white cells and platelets.
Gene involved: JAK2 mutation (in ~95% of cases).
Symptoms:
-Itchy skin (particularly after hot baths)
-Headaches
-Dizziness
-High blood pressure
-Vision disturbances
-Enlarged spleen
Risks:
-Blood clots
-Stroke or heart attack
-Evolution to leukemia in exceptional cases
Diagnosis:
-High RBC, hemoglobin, hematocrit
-Low erythropoietin (EPO) levels
-JAK2 mutation test
5. Secondary Polycythemia: A Reaction to External Stimuli
This occurs when the body overproduces RBCs to counteract other conditions.
A. Chronic Hypoxia (Low Oxygen)
Your body overproduces RBCs to enhance oxygen delivery.
Causes include:
-Chronic obstructive pulmonary disease (COPD)
-Pulmonary fibrosis
-Congenital heart disease
-Residing at high altitudes
B. Tumors Producing Erythropoietin (EPO)
Certain tumors are capable of producing excess EPO, including:
-Renal cell carcinoma (kidney cancer)
-Liver tumors
-Uterine fibroids
-Adrenal tumors
C. Carbon Monoxide Exposure
Source: Smoking, pollution, faulty heaters
-Carbon monoxide decreases oxygen transport by sequestering hemoglobin, which stimulates more RBC production.
D. Anabolic Steroid and Testosterone Abuse
-These drugs may stimulate erythropoiesis (red blood cell production).
-Seen in bodybuilders or individuals on hormone therapy.
E. Genetic Etiology / Congenital Polycythemia
Rare genetic disorders that make the body produce more RBCs due to:
-High-affinity hemoglobin
-Erythropoietin receptor mutations
6. Signs and symptoms of an Elevated RBC Count
Some individuals are asymptomatic, particularly if the increase is gradual. Symptoms do occur, however:
-Fatigue
-Headaches
-Blurred vision
-Dizziness
-Red skin (particularly the face)
-Numbness or tingling in the extremities
-High blood pressure
-Shortness of breath
-Itchiness (particularly after a hot shower)
7. Complications of High Red Blood Cell Counts
Too many red blood cells thicken the blood (hyperviscosity), making it more prone to:
-Blood clots
-Stroke
-Heart attack
-Deep vein thrombosis (DVT)
-Pulmonary embolism
-Enlarged spleen
-Bleeding or bruising (paradoxically)
8. Diagnosis: How Doctors Identify the Cause
Physicians will evaluate the cause of an elevated RBC count with a combination of:
A. Medical History
-Smoking?
-Exposure to high altitude?
-Use of steroids or testosterone?
-Symptoms of sleep apnea?
B. Physical Exam
-Flushed face
-Enlarged spleen
-Signs of oxygen deprivation
C. Blood Tests
-CBC (complete blood count)
-Erythropoietin (EPO) level
-Oxygen saturation
-JAK2 mutation testing (for PV)
-Iron studies (polycythemia vera can decrease iron)
D. Imaging
-Chest X-ray or CT scan (lung disease)
-Abdominal ultrasound or MRI (kidney/liver tumors)
E. Sleep Studies
Used if sleep apnea is suspected.
9. Treatment: Targeting the Cause, Not Just the Numbers
A. If Caused by Dehydration:
-Oral or IV hydration
-Correct underlying causes (fever, vomiting, diuretics)
B. If Caused by Polycythemia Vera:
-Phlebotomy (draining blood to decrease RBCs)
-Low-dose aspirin (prevention of clots)
-Drugs such as hydroxyurea to inhibit bone marrow
C. If Caused by Lung or Heart Disease:
-Oxygen therapy
-Treatment of underlying disease
D. If Caused by Sleep Apnea:
-CPAP machine
-Weight loss if applicable
E. If Caused by Tumors:
-Surgical removal
-Chemotherapy or radiation (if necessary)
F. If Due to Smoking or Exposure to Environment:
-Quitting smoking
-Improve ventilation, eliminate sources of carbon monoxide
10. Lifestyle Advice for Dealing with or Avoiding High RBC Count
-Drink regularly, particularly in hot climates or when ill.
-Smoking and second-hand smoke avoidance.
-Avoid taking performance-enhancing drugs except on medical grounds.
-Regular check-ups if you have chronic respiratory, cardiac, or renal disease.
-Treat sleep apnea — untreated will result in severe complications.
-Know your family history — inherited causes should be monitored early.
11. When to See a Doctor
See your doctor if:
-Your routine blood test shows a persistently high RBC count.
-You have symptoms like dizziness, headaches, or vision problems.
-You experience unexplained fatigue or breathing issues.
-You’re at risk (e.g., smoker, high-altitude dweller, chronic illness).
Conclusion: What Causes High Red Blood Cell Count
Although dehydration is a common and normally benign explanation for elevated RBC count, one should not ignore potentially more dangerous conditions. Chronic or markedly elevated levels of RBC must be subjected to medical examination to exclude underlying conditions like polycythemia vera, chronic hypoxia, tumors, or endocrine disorders.
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