Test Description

What is MCHC?

Mean Corpuscular Hemoglobin Concentration (MCHC) measures the average concentration of hemoglobin within red blood cells. Unlike MCH (which measures total hemoglobin per cell), MCHC measures how "concentrated" the hemoglobin is relative to cell volume.

How is MCHC Calculated?

MCHC is calculated using the formula:

MCHC (g/dL) = (Hemoglobin in g/dL ÷ Hematocrit %) × 100

Or equivalently: MCHC = MCH ÷ MCV × 100

For example, if Hemoglobin = 14 g/dL and Hematocrit = 42%:

MCHC = (14 ÷ 42) × 100 = 33.3 g/dL (normal)

Understanding the Three RBC Indices

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Index Measures Units Think of it as...
MCV Cell size (volume) fL How BIG is the cell?
MCH Hemoglobin mass per cell pg How much Hgb is IN the cell?
MCHC Hemoglobin concentration g/dL How CONCENTRATED is the Hgb?
Why MCHC Matters: MCHC is the most stable of the RBC indices and is particularly useful for detecting spherocytosis. An elevated MCHC (>36 g/dL) is one of the most sensitive screening tests for hereditary spherocytosis.
Quick Reference
  • Normal Range: 32-36 g/dL (or 320-360 g/L)
  • Low MCHC: <32 g/dL (hypochromic - dilute hemoglobin)
  • High MCHC: >36 g/dL (hyperchromic - concentrated hemoglobin)
  • Primary Use: Detect hemoglobin concentration abnormalities; key marker for spherocytosis
  • Sample Type: Whole blood (EDTA tube - purple top)
  • Key Point: MCHC >36 g/dL is a red flag for spherocytosis or technical error
Normal Ranges

MCHC is relatively stable across age groups compared to other RBC indices.

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Age Group Normal MCHC (g/dL) Notes
Adults 32-36 Standard reference range
Newborns 31-35 Slightly lower
Infants 30-36 Wide range
Children 32-36 Similar to adults

MCHC Physiologic Limits

There are physiologic constraints on MCHC:

  • Lower limit (~28-30 g/dL): Below this, RBCs cannot carry sufficient oxygen
  • Upper limit (~37-38 g/dL): Hemoglobin crystallization would occur at higher concentrations
Critical Values:
  • MCHC >37 g/dL: Either spherocytosis or technical artifact (cold agglutinins, lipemia)
  • MCHC <28 g/dL: Severe hypochromia; usually severe iron deficiency
Clinical Significance

Low MCHC (<32 g/dL) - Hypochromia

Low MCHC indicates that hemoglobin is "diluted" within the cell, typically due to impaired hemoglobin synthesis:

Iron Deficiency Anemia:

  • Most common cause of low MCHC
  • Insufficient iron → insufficient hemoglobin synthesis
  • Low MCV + Low MCH + Low MCHC = classic triad
  • Peripheral smear shows hypochromic, microcytic cells with increased central pallor

Thalassemia:

  • Defective globin chain synthesis
  • MCHC may be low-normal or mildly low
  • MCV disproportionately low compared to MCHC

Sideroblastic Anemia:

  • Defective iron utilization in mitochondria
  • Iron accumulates but cannot be incorporated into hemoglobin
  • Dimorphic RBC population may be present

High MCHC (>36 g/dL) - Hyperchromia

Elevated MCHC is less common and has a limited differential:

Hereditary Spherocytosis:

  • Most important cause of elevated MCHC
  • Membrane defect causes loss of cell surface area
  • Same hemoglobin content in smaller volume = higher concentration
  • MCHC typically 35-38 g/dL
  • Spherocytes on peripheral smear; elevated reticulocyte count
  • Positive osmotic fragility test

Autoimmune Hemolytic Anemia (Warm Type):

  • Antibody-coated RBCs undergo partial phagocytosis
  • Results in spherocyte formation
  • Positive direct Coombs test

Severe Burns:

  • Thermal damage to RBC membrane
  • Spherocytes and fragmented cells
Technical Artifacts Causing Falsely Elevated MCHC:
  • Cold agglutinins: Most common cause of spurious high MCHC; RBC clumping decreases apparent hematocrit
  • Lipemia: Turbidity falsely elevates hemoglobin measurement
  • Hemolysis: In vitro hemolysis affects hemoglobin reading
  • High WBC count: Extreme leukocytosis can interfere
Interpretation Guidelines

Approach to Elevated MCHC

Step 1: Rule out technical artifact

  • Check for lipemia (cloudy sample)
  • Warm sample to 37°C and repeat if cold agglutinins suspected
  • Check for hemolysis (pink/red serum)

Step 2: If confirmed elevated, evaluate for hemolysis

  • Reticulocyte count (elevated in hemolysis)
  • LDH (elevated)
  • Indirect bilirubin (elevated)
  • Haptoglobin (decreased)

Step 3: Peripheral blood smear review

  • Spherocytes: Small, round, lack central pallor
  • Polychromasia: Bluish tinge indicates reticulocytes

Step 4: Further testing if spherocytes present

  • Direct Coombs test (DAT) - to distinguish immune from hereditary
  • If DAT negative → consider hereditary spherocytosis
  • If DAT positive → autoimmune hemolytic anemia

MCHC in Context of Other Indices

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Pattern MCV MCH MCHC Suggests
Hypochromic Microcytic ↓ ↓ ↓ Iron deficiency
Normochromic Normocytic N N N Acute blood loss, CKD
Macrocytic ↑ ↑ N B12/folate deficiency
Spherocytosis N/↓ N ↑ HS or AIHA
Interfering Factors

Falsely Elevated MCHC

  • Cold agglutinins: RBC clumping at room temperature reduces measured hematocrit, falsely elevating MCHC; resolves when sample warmed to 37°C
  • Lipemia: Turbidity causes falsely elevated hemoglobin reading
  • Hyperbilirubinemia: Severe jaundice may affect optical readings
  • In vitro hemolysis: Free hemoglobin measured but cells not present
  • Paraproteins: Monoclonal proteins may interfere

Falsely Decreased MCHC

  • Sample age: RBCs swell with prolonged storage, increasing apparent volume
  • Hyperglycemia: Osmotic swelling of RBCs

How to Identify Artifacts

  • MCHC >37 g/dL without spherocytes on smear → likely artifact
  • Check if MCV and RBC count are also abnormal in a consistent pattern
  • Request sample warming if cold agglutinins suspected
  • Check specimen for lipemia, hemolysis, icterus
Clinical Pearls
MCHC is the spherocytosis detector: Elevated MCHC (>35.5-36 g/dL) has >70% sensitivity for hereditary spherocytosis. In a patient with anemia, hemolysis markers, and elevated MCHC, spherocytosis should be at the top of your differential.
MCHC is the most stable index: Unlike MCV and MCH, MCHC stays within a narrow physiologic range because cells cannot tolerate hemoglobin concentrations that are too dilute or too concentrated. This stability makes it useful for quality control.
Cold agglutinin tip: If you see MCHC >37 g/dL with normal peripheral smear (no spherocytes), think cold agglutinins. This is especially common in elderly patients or those with Mycoplasma pneumoniae infection or lymphoproliferative disorders.
Don't overlook family history: Hereditary spherocytosis is autosomal dominant. If you suspect HS in a patient, ask about family history of anemia, jaundice, gallstones at young age, or splenectomy.
MCHC and transfusion: In patients with chronic hemolytic anemias and elevated MCHC, transfused normal RBCs will have normal MCHC. The post-transfusion MCHC reflects the mixture of patient and donor cells.
Low MCHC = look at the smear: The peripheral smear equivalent of low MCHC is hypochromia - RBCs with expanded central pallor (>1/3 of cell diameter). Iron deficiency shows marked hypochromia; thalassemia shows target cells with variable hypochromia.
References
  1. Kratz, A., Ferraro, M., Sluss, P. M., & Lewandrowski, K. B. (2004). Laboratory reference values. New England Journal of Medicine, 351, 1548-1564.
  2. Bolton-Maggs, P. H. B., et al. (2012). Guidelines for the diagnosis and management of hereditary spherocytosis. British Journal of Haematology, 156(1), 37-49.
  3. Mariani, M., et al. (2008). Clinical and hematologic features of 300 patients affected by hereditary spherocytosis grouped according to the type of the membrane protein defect. Haematologica, 93(9), 1310-1317.
  4. Buttarello, M., & Plebani, M. (2008). Automated blood cell counts: state of the art. American Journal of Clinical Pathology, 130(1), 104-116.
  5. Ford, J. (2013). Red blood cell morphology. International Journal of Laboratory Hematology, 35(3), 351-357.
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  • For Educational Purposes Only: This content is intended for educational reference and should not be used for clinical decision-making.
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The clinical content and references are curated and reviewed by myself; however, AI was used to assist in organizing, paraphrasing, and formatting the information presented.