Treatment Approach for Elevated Hematocrit with Low MCHC
The first priority is to assess hydration status and rule out iron deficiency before considering any intervention, as therapeutic phlebotomy is only indicated when hemoglobin exceeds 20 g/dL and hematocrit exceeds 65% with hyperviscosity symptoms. 1
Initial Assessment and Rehydration
Your patient's hematocrit of 48.6% and hemoglobin of 14.9 g/dL do not meet criteria for therapeutic phlebotomy. The low MCHC (30.7 g/dL) strongly suggests iron deficiency, which paradoxically worsens oxygen delivery despite elevated hematocrit. 1
Immediate steps:
- Rehydrate first with oral fluids or intravenous normal saline as first-line therapy before any other intervention 1
- The elevated hematocrit may represent relative polycythemia from dehydration rather than true erythrocytosis 2
- Dehydration is a common cause of elevated hematocrit that resolves with fluid replacement 1
Evaluate for Iron Deficiency
Order the following laboratory tests: 2
- Serum ferritin and transferrin saturation to confirm iron deficiency 1, 2
- Mean corpuscular volume (MCV) alone is not reliable for screening iron deficiency in erythrocytosis 1
- Reticulocyte count and C-reactive protein 2
Critical point: Iron deficiency causes microcytosis without proportional hematocrit reduction, compromising oxygen transport and increasing stroke risk 1, 3. The low MCHC in your patient is a red flag for this condition.
Treatment Based on Iron Status
If Iron Deficiency Confirmed (Transferrin Saturation <20%)
Iron supplementation is indicated but requires careful monitoring: 1
- Treat until iron stores are replete (normal ferritin and transferrin saturation) 1
- Monitor hemoglobin closely during supplementation as rapid increases in red cell mass can occur 1, 3
- Once iron stores normalize, discontinue supplementation 1
- Consider combining cautious iron supplementation with monitoring rather than phlebotomy 3
If No Iron Deficiency
Investigate secondary causes of erythrocytosis: 2
- Sleep study if nocturnal hypoxemia suspected 2
- Evaluate for chronic obstructive pulmonary disease, smoking history 2
- Consider testosterone use (prescribed or unprescribed) 2
- Test for JAK2 mutations if primary polycythemia vera suspected 2
When Phlebotomy Is NOT Indicated
Avoid phlebotomy in your patient because: 1
- Hemoglobin is only 14.9 g/dL (threshold is >20 g/dL) 1
- Hematocrit is 48.6% (threshold is >65%) 1
- Repeated routine phlebotomies are contraindicated due to risk of iron depletion, decreased oxygen-carrying capacity, and stroke 1
- Iron deficiency from inappropriate phlebotomy is the strongest predictor of cerebrovascular events 1
Critical Pitfalls to Avoid
Do not perform phlebotomy based solely on hematocrit levels below 65% - this causes more harm than benefit through iron depletion 1. The relationship between hematocrit and viscosity is complex, and arbitrary cutoffs are not supported by evidence 1, 4.
Do not overlook coexisting iron deficiency - the low MCHC suggests this is already present and requires correction, not worsening through phlebotomy 1, 3.