Interpretation of Elevated Hematocrit and Low MCHC

Understanding the Abnormal Values

A hematocrit of 47.8% is above the high normal range, indicating a relative increase in the proportion of red blood cells in the blood volume, according to the Mayo Clinic Proceedings 1
The MCHC of 29.7% is below the low normal range, suggesting decreased hemoglobin concentration within red blood cells, as reported in JAMA 2
Other values including hemoglobin, MCV, and RBC count are within normal ranges, as noted in the American Journal of Kidney Diseases 3

Dehydration is the most common cause of relative polycythemia, resulting from plasma volume depletion while red cell mass remains constant, as stated in the Mayo Clinic Proceedings 4
Low MCHC typically indicates hypochromia, most commonly seen in iron deficiency, according to MMWR Recommendations and Reports 5
The combination with normal MCV suggests early iron deficiency before microcytosis develops, as reported in MMWR Recommendations and Reports 5

Assess for dehydration by reviewing clinical signs and obtaining history of fluid intake, losses, and medication use, as recommended in the Mayo Clinic Proceedings 4
Evaluate for true vs. relative polycythemia by rechecking CBC after adequate hydration, as suggested in the Mayo Clinic Proceedings 1
Investigate iron status by ordering serum ferritin, iron, total iron binding capacity, and transferrin saturation, as recommended in MMWR Recommendations and Reports 5

Mild elevation of hematocrit with low MCHC is unlikely to cause significant clinical symptoms, as noted in the Mayo Clinic Proceedings 7
If dehydration is confirmed, increase oral fluid intake or provide IV fluids if necessary, and address underlying causes of fluid loss, as recommended in the Mayo Clinic Proceedings 4
If iron deficiency is confirmed, initiate oral iron supplementation and investigate potential causes of iron deficiency, as suggested in MMWR Recommendations and Reports 5

Repeat CBC after ensuring adequate hydration, as recommended in the Mayo Clinic Proceedings 1
If hematocrit normalizes but MCHC remains low, proceed with iron studies, as suggested in MMWR Recommendations and Reports 5
If hematocrit remains elevated despite adequate hydration, consider evaluation for true polycythemia, as recommended in the Mayo Clinic Proceedings 6, 7