What does a hemoglobin level of 17.9 in a man indicate?

Hemoglobin 17.9 g/dL in a Man: Clinical Significance

A hemoglobin level of 17.9 g/dL in a man is elevated but falls within the normal range for healthy young men at high altitude (up to 21 g/dL), though it exceeds typical sea-level norms and warrants evaluation for secondary causes of erythrocytosis, particularly hypoxia-related conditions. 1, 2

Normal Reference Ranges and Context

• The standard definition of anemia uses hemoglobin <13.5 g/dL in adult males, which implies that normal values extend above this threshold 1
• At sea level, the mean hemoglobin for adult males is approximately 14.6-15.4 g/dL, with the 95th percentile reaching 16.7-17.0 g/dL 1
• For healthy young men living at 4000 meters altitude, the normal range extends from 13 to 21 g/dL, making 17.9 g/dL completely normal in that context 2
• A hemoglobin of 17.9 g/dL does not meet criteria for significant erythrocytosis requiring hematologic workup (>185 g/L or 18.5 g/dL in men) 3

Clinical Approach to Elevated Hemoglobin

Determine if this represents true erythrocytosis versus relative erythrocytosis:

• Measure hematocrit to confirm elevation (normal male hematocrit at sea level is typically <52%, while at 4000m it averages 52.7% with upper limit of 61%) 2
• Consider that plasma volume contraction can cause elevated hemoglobin concentration without increased total hemoglobin mass 4
• In patients with heart failure or liver disease, hemoglobin concentration correlates poorly with actual hemoglobin mass (r=0.312 and r=0.410 respectively), as plasma volume expansion or contraction drives the concentration 4

Differential Diagnosis and Workup

If confirmed as true elevation, evaluate for secondary causes first:

• Hypoxia is the most frequent etiology in young adults with secondary erythrocytosis 3
• Assess for: chronic lung disease, sleep apnea, smoking history (59% of young adults with erythrocytosis are smokers), high altitude residence, or cyanotic heart disease 3
• Evaluate for obesity (43% of young adults with erythrocytosis are obese) and substance use (38% use excess alcohol or recreational drugs) 3

Molecular testing considerations:

• JAK2 V617F mutation is found in only 10.9% of patients referred for elevated hemoglobin 5
• JAK2 testing and serum erythropoietin levels are performed in only 17.9% and 23.2% of cases respectively in clinical practice, representing underutilization 3
• Additional mutations (TET2, DNMT3A, ASXL1) are found in 34.5% of JAK2-positive patients and 6% of JAK2-negative patients with erythrocytosis 5

Common Pitfalls to Avoid

• Do not assume polycythemia vera without JAK2 testing - no primary erythrocytosis was found in a cohort of 56 young adults with elevated hemoglobin 3
• Do not overlook relative erythrocytosis - 7 of 56 patients (12.5%) had relative rather than absolute erythrocytosis 3
• Recognize that 24 of 56 patients (43%) had no identifiable cause after initial workup 3
• Less than half of patients receive appropriate long-term follow-up after initial investigations 3

Management Implications

• At 17.9 g/dL, this level does not require phlebotomy or aspirin therapy unless other risk factors for thrombosis are present 3
• Focus on identifying and treating underlying secondary causes rather than the hemoglobin elevation itself 3
• If no cause is identified and the patient remains asymptomatic, observation with periodic monitoring is appropriate 3