How should a hemoglobin level of 165 g/L be interpreted and managed in a 40‑year‑old woman?

Hemoglobin 165 g/L in a 40-Year-Old Woman

A hemoglobin of 165 g/L in a 40-year-old woman is elevated and warrants investigation for secondary causes of erythrocytosis, particularly hypoxia-related conditions, before considering primary polycythemia vera.

Interpretation of the Hemoglobin Level

Based on normative data for women aged 40-49 years, a hemoglobin of 165 g/L falls at approximately the 95th percentile (the upper limit of normal ranges from 143.5-151.0 g/L depending on the population studied) 1. This represents true erythrocytosis that requires evaluation.

For context, polycythemia vera diagnostic criteria require hemoglobin >160 g/L in women as one of the major criteria 2. Your patient's value of 165 g/L exceeds this threshold and cannot be dismissed as normal variation.

Critical Factors to Assess Immediately

Altitude and smoking status are the two most important modifying factors:

• Altitude adjustment: If living above 1,000 meters elevation, add 0.2-1.9 g/dL to the expected normal range depending on altitude 1. At 1,500 meters, add 0.5 g/dL; at 2,000 meters, add 0.8 g/dL.

• Smoking adjustment: Active smokers have physiologically elevated hemoglobin. Add 0.3 g/dL for light smokers (0.5-1 pack/day), 0.5 g/dL for moderate smokers (1-2 packs/day), or 0.7 g/dL for heavy smokers (>2 packs/day) 1.

If she smokes 1 pack daily and lives at sea level, her "adjusted" hemoglobin would be 165 - 3 = 162 g/L, still elevated but less concerning.

Diagnostic Workup Algorithm

Step 1: Distinguish Absolute vs Relative Erythrocytosis

• Check hematocrit: If >48% in women, confirms erythrocytosis 2
• Assess volume status: Relative erythrocytosis (Gaisböck syndrome) occurs with dehydration, diuretic use, obesity, or hypertension
• In a retrospective study of young adults with elevated hemoglobin, 25/56 (45%) had absolute erythrocytosis, 7/56 (12.5%) had relative erythrocytosis, and 24/56 (43%) remained undiagnosed 3

Step 2: Screen for Secondary Causes (Most Common)

Hypoxia-related causes are the most frequent etiology in young adults with secondary erythrocytosis 3:

• Smoking history (59% of cases in one series)
• Obesity and sleep apnea (43% were obese)
• Chronic lung disease (COPD, interstitial lung disease)
• Cardiac right-to-left shunts
• High altitude residence
• Carbon monoxide exposure

Other secondary causes:

• Renal pathology: Renal artery stenosis, polycystic kidney disease, renal tumors
• Erythropoietin-secreting tumors: Hepatocellular carcinoma, renal cell carcinoma, uterine fibroids, cerebellar hemangioblastoma
• Exogenous erythropoietin or testosterone use

Step 3: Laboratory Evaluation

Essential initial tests:

1. Serum erythropoietin (EPO) level - This is the critical discriminator:

   • Low or inappropriately normal EPO → suggests primary polycythemia vera
   • Elevated EPO → suggests secondary erythrocytosis or EPO-producing tumor 4
   • Only 23.2% of patients in one series had EPO measured, representing a significant gap in care 3

2. JAK2 V617F mutation testing:

   • Positive in ~95% of polycythemia vera cases 2
   • If negative, consider JAK2 exon 12 mutation testing
   • Only 17.9% of patients in one series were tested, another major care gap 3

3. Iron studies (ferritin, transferrin saturation):

   • Iron deficiency can mask polycythemia vera
   • One case report documented elevated hemoglobin with concurrent iron deficiency due to EPO-producing plasma cell dyscrasia 4

4. Oxygen saturation (pulse oximetry and arterial blood gas if indicated)

Step 4: Risk Stratification

If polycythemia vera is confirmed (JAK2 positive, low EPO, hemoglobin >160 g/L):

• Thrombotic risk is the primary concern affecting morbidity and mortality
• Age ≥60 years or prior thrombosis = high risk
• Your 40-year-old patient would be low-risk based on age alone
• Treatment goal: Maintain hematocrit <45% to reduce thrombotic complications

Management Approach

If Secondary Erythrocytosis is Identified:

Treat the underlying cause:

• Smoking cessation
• CPAP for sleep apnea
• Optimize chronic lung disease management
• Surgical correction of cardiac shunts if feasible
• Remove EPO-producing tumors

Phlebotomy is rarely needed unless hemoglobin exceeds 180-185 g/L in men or 165-170 g/L in women with symptoms

If Polycythemia Vera is Diagnosed:

Immediate management:

• Low-dose aspirin 81-100 mg daily (reduces thrombotic risk) 3
• Phlebotomy to target hematocrit <45% 3
• Remove 250-500 mL every 2-3 days initially, then as needed

Long-term management:

• Continue aspirin indefinitely
• Periodic phlebotomy to maintain hematocrit <45%
• Cytoreductive therapy (hydroxyurea) if high-risk features develop

Common Pitfalls to Avoid

1. Failing to adjust for altitude and smoking - This leads to over-diagnosis of pathologic erythrocytosis

2. Not measuring EPO levels - This is the single most important test to distinguish primary from secondary causes, yet was only done in 23% of cases in one series 3

3. Not testing for JAK2 mutations - Essential for diagnosing polycythemia vera, but only performed in 18% of cases 3

4. Assuming "normal aging" - Hemoglobin concentrations in women remain stable between ages 20-80 years; elevated values always warrant investigation 1

5. Inadequate follow-up - Less than half of patients in one cohort had long-term follow-up after initial investigations 3, representing a significant quality gap

6. Treating with phlebotomy before establishing diagnosis - Only 5 patients in one series received phlebotomy, and management was often discordant with guidelines 3

Bottom Line

For this 40-year-old woman with hemoglobin 165 g/L: Measure serum EPO and test for JAK2 V617F mutation while simultaneously evaluating for hypoxia-related secondary causes (smoking, obesity/sleep apnea, lung disease). If EPO is elevated and JAK2 is negative, pursue imaging to exclude EPO-secreting tumors. If EPO is low/normal and JAK2 is positive, diagnose polycythemia vera and initiate aspirin with phlebotomy targeting hematocrit <45%. The goal is preventing thrombotic complications that significantly impact morbidity and mortality.