What does an MCHC (Mean Corpuscular Hemoglobin Concentration) of 30.9 indicate?

MCHC 30.9 g/dL Interpretation

An MCHC of 30.9 g/dL is at the lower end of the normal reference range (32-36 g/dL) and suggests possible hypochromia, which most commonly indicates iron deficiency or thalassemia trait, though it may also be within normal variation depending on the analyzer and patient context.

Normal Reference Range Context

• MCHC normal range is typically 32-36 g/dL, with values below 32 g/dL considered hypochromic 1
• Your value of 30.9 g/dL falls just below this threshold, indicating mild hypochromia 1
• MCHC values are generally stable and less affected by technical factors than other red cell indices, making this finding clinically relevant 1

Most Likely Causes of Low-Normal MCHC

Iron Deficiency (Most Common)

• Mean corpuscular hemoglobin (MCH) may be more sensitive than MCHC for detecting iron deficiency, as it decreases in both absolute and functional iron deficiency 1
• Hypochromia (low MCHC) combined with microcytosis (low MCV) strongly suggests iron deficiency in the absence of chronic disease 1
• Check serum ferritin as the most specific test: values <15 μg/L indicate absent iron stores, while <30 μg/L suggest low body iron stores 1
• In the presence of inflammation, ferritin <45 μg/L may still indicate iron deficiency despite being "normal" 1

Thalassemia Trait

• Thalassemia typically shows MCV reduced out of proportion to the degree of anemia, with MCHC also decreased 1
• If iron studies are normal but MCHC remains low with microcytosis, hemoglobin electrophoresis is recommended, particularly in patients of Mediterranean, African, Middle Eastern, or Southeast Asian descent 1

Anemia of Chronic Disease

• Both microcytosis and hypochromia lose sensitivity for iron deficiency when chronic inflammatory conditions are present 1
• Ferritin may be falsely elevated as an acute phase reactant, masking underlying iron deficiency 1

Critical Next Steps

Order the following tests immediately:

1. Complete blood count with full indices to evaluate MCV, MCH, and red cell distribution width (RDW) 1
2. Serum ferritin (most specific for iron deficiency) 1
3. Transferrin saturation (TSAT) - values <20% suggest iron deficiency 1
4. Peripheral blood smear to assess red cell morphology and confirm hypochromia 1, 2

Important Caveats

• Technical interference can cause false MCHC values: cold agglutinins and lipemia can artificially elevate MCHC, though your value is low rather than high 3
• MCHC values significantly above 36 g/dL are not physiologically possible due to hemoglobin solubility limits and suggest technical error 3, 2
• In patients with chronic kidney disease, MCHC should be interpreted alongside hemoglobin targets of 11-12 g/dL (Hct 33-36%) 1, 4

When to Investigate Further

Proceed with gastrointestinal evaluation if:

• Ferritin <45 μg/L in the context of unexplained anemia 1
• Male patient or postmenopausal female with confirmed iron deficiency 1
• Premenopausal women with iron deficiency AND gastrointestinal symptoms or family history of GI pathology 1
• Screen for celiac disease serologically, as it is found in 3-5% of iron deficiency anemia cases 1

Do NOT routinely investigate GI tract in:

• Premenopausal women with non-anemic iron deficiency without other concerning features, as menstrual blood loss is the likely cause 1