What are the common causes and management of elevated hemoglobin (HGB), red blood cell (RBC) count, and hematocrit (HCT)?

Common Causes of Elevated Hemoglobin, RBC, and Hematocrit

Your elevated values (Hemoglobin 16.6 g/dL, RBC 5.33, Hematocrit 50.9%) require systematic evaluation to distinguish between relative polycythemia (dehydration), secondary erythrocytosis (physiological response to low oxygen or other conditions), and primary polycythemia vera (bone marrow disorder). 1

Initial Assessment Steps

First, confirm these are truly elevated values by repeating the measurements, as a single measurement can be unreliable and may reflect temporary dehydration or laboratory variation. 1, 2

Evaluate for Relative Polycythemia (Most Common)

• Assess your hydration status - dehydration, diuretic use, or inadequate fluid intake can concentrate your blood and falsely elevate all three values 1
• Consider stress polycythemia (Gaisböck syndrome) - occurs in anxious, hypertensive individuals with plasma volume depletion 1
• If dehydration is suspected, recheck values after adequate hydration 2

Screen for Secondary Causes (Next Most Common)

Secondary erythrocytosis represents your body's normal response to low oxygen or other stimuli. Common causes include:

Hypoxia-Related Causes

• Smoking - causes "smoker's polycythemia" through chronic carbon monoxide exposure, which stimulates red blood cell production and resolves with smoking cessation 1, 2
• Sleep apnea - nocturnal oxygen drops drive increased red blood cell production 1, 2
• Chronic lung disease (COPD) - persistent low oxygen levels trigger compensatory erythrocytosis 1
• Living at high altitude - normal physiological adaptation (hemoglobin increases 0.2-4.5 g/dL depending on altitude) 1

Other Secondary Causes

• Testosterone use (prescribed or unprescribed) - very common cause in young adults, with 43.8% incidence of elevated hematocrit 1, 3
• Kidney disease - abnormal erythropoietin production 1
• Certain tumors - renal cell carcinoma, liver cancer, or other malignancies producing erythropoietin 1

Rule Out Polycythemia Vera (Least Common but Most Serious)

Polycythemia vera is a bone marrow disorder requiring hematologist evaluation. 1, 2

Recommended Laboratory Workup

Order these tests to determine the cause: 1

• Complete blood count with differential - evaluate white blood cells and platelets (elevated in polycythemia vera)
• Serum ferritin and transferrin saturation - iron deficiency can coexist with erythrocytosis
• C-reactive protein (CRP) - assess for inflammation
• JAK2 mutation testing - positive in 95% of polycythemia vera cases 1, 3
• Serum erythropoietin level - low suggests polycythemia vera, normal/high suggests secondary cause 3

When to Worry and Seek Specialist Care

Refer to hematology if: 1, 2

• JAK2 mutation is positive
• No secondary cause identified
• Hemoglobin >18.5 g/dL (men) or >16.5 g/dL (women)
• Hematocrit >55% (men) or >49.5% (women)
• Associated symptoms: severe headaches, dizziness, visual changes, itching after warm showers, or unexplained blood clots

Important Management Principles

Do NOT undergo routine phlebotomy (blood removal) without clear indication, as this can cause iron deficiency, reduce oxygen-carrying capacity, and paradoxically increase stroke risk. 1, 2

Phlebotomy is only indicated when: 1, 2

• Hemoglobin >20 g/dL AND hematocrit >65%
• Symptoms of hyperviscosity (severe headache, confusion, vision changes)
• You are adequately hydrated
• No iron deficiency is present

If polycythemia vera is diagnosed, target hematocrit must be kept strictly below 45% through regular phlebotomy, as this reduces cardiovascular death and major blood clots from 9.8% to 2.7%. 2

Common Pitfalls to Avoid

• Don't assume dehydration without confirming - drink adequate fluids and recheck values 1
• Don't ignore smoking history - this is a reversible cause 1, 2
• Don't overlook sleep apnea symptoms - snoring, daytime fatigue, witnessed breathing pauses 1
• Don't forget to ask about testosterone use - including supplements or "performance enhancers" 1
• Don't allow iron deficiency to develop - even with elevated counts, iron-deficient red blood cells carry less oxygen and increase stroke risk 1, 2

Next Steps Summary

1. Ensure adequate hydration and repeat labs in 1-2 weeks 1
2. Complete the recommended laboratory workup (ferritin, JAK2, erythropoietin) 1, 3
3. Address modifiable causes - stop smoking, treat sleep apnea, adjust testosterone if applicable 1, 2
4. See a hematologist if JAK2 positive or no secondary cause found 1, 2
5. Monitor cardiovascular risk factors - blood pressure, cholesterol, diabetes 2