Bedside Snapshot

Normal (Adult): 32–36 g/dL (320–360 g/L)
Newborns and children: similar, mean about 34 g/dL; use the lab's age-specific range
Critical Values: No universal critical value: interpret by trend and clinical context. Analyzers flag about >36–37.5 or <28 g/dL for lab review (typical; lab-specific).
High Suggests: Artifact first: cold agglutinins, lipemia, hemolyzed sample, hyponatremia
True: intravascular hemolysis, warm AIHA, hereditary spherocytosis, sickle cell or HbSC disease
Low Suggests: Iron deficiency (most common), thalassemia (often only mildly low), sideroblastic anemia
Artifact: glucose ≥600 mg/dL, sample stored 1–4 days, hypernatremia
Act Now If: High MCHC with pink plasma, falling Hb, dark urine or jaundice: treat as active hemolysis; stop any running transfusion, send hemolysis labs, DAT and smear; notify medical control or the receiving team
Watch Out For: MCHC >36 g/dL with a normal smear is usually artifact (cold agglutinins, lipemia, hemolysis); have the lab warm or correct the sample before a spherocytosis workup

Reference & Critical Ranges

Lab-specific ranges: Every lab sets its own interval, based on its analyzer and its population. Your lab report's range wins. The values below are typical.

Reference ranges

Population	Conventional	SI	Notes
Adult	32–36 g/dL	320–360 g/L	Same for men and women
Pregnancy	Same as adult	Same as adult	A low MCHC with a low MCV points to iron deficiency, which is common in pregnancy
Older adult	Same as adult	Same as adult	New hypochromia needs an iron and blood-loss workup
Neonate 0–28 d	Mean about 34 g/dL	Mean about 340 g/L	Does not vary with gestational age; somewhat higher values can occur in healthy neonates, so use the lab's neonatal interval
Infant and child	Similar to adult	Similar to adult	Some labs use a slightly lower limit in infancy; use the lab's age-specific interval

Severity & critical values

Level	Conventional	SI	What it means
Low (hypochromia)	<32 g/dL	<320 g/L	Iron deficiency most likely; thalassemia trait is often normal or only mildly low
Marked low (lab flag)	<28 g/dL	<280 g/L	Advanced iron deficiency or interference; many analyzers flag for review
High	>36 g/dL	>360 g/L	Exclude artifact first, then spherocytes, intravascular hemolysis or sickle cell/HbSC disease
High (lab flag)	>36–37.5 g/dL	>360–375 g/L	Analyzer-specific review threshold; the lab checks the sample and may correct and rerun
Critical	None universal	None universal	No panic value; interpret by trend and clinical context (typical; lab-specific)

Critical values: There is no universal critical value for MCHC. Read the trend and the patient. Analyzers flag about >36–37.5 or <28 g/dL for lab review (typical, lab-specific). A flag means check the sample first. The danger is the hemolysis or anemia behind the number.

Conversion: g/dL × 10 = g/L

MCHC

MCHC (g/dL) = Hb (g/dL) ÷ Hct (%) × 100 = MCH (pg) ÷ MCV (fL) × 100

Normal: 32–36 g/dL. Example: Hb 14 g/dL and Hct 42% give 33.3 g/dL.

Causes of Abnormal Results

High (hyperchromia >36 g/dL)

Before you believe a high value, rule out a bad result. Most high values come from the sample or the analyzer, not the patient.

Mechanism	Common causes	Bedside clue
Spurious: red cell clumping lowers RBC count and Hct	Cold agglutinins (Mycoplasma pneumonia, cytomegalovirus, cold agglutinin disease)	MCV also high, RBC count low; clumps on smear; corrects when the tube is warmed to 37 °C (98.6 °F)
Spurious: turbidity or color falsely raises Hb	Lipemia (markedly elevated triglycerides; threshold is analyzer-specific, often above 1,000–2,000 mg/dL), lipid infusions, marked hyperbilirubinemia, IgM paraprotein, cryoglobulins	Milky or deep-yellow plasma; Hb out of step with Hct
Spurious: cells lyse in the tube, Hb still counted	In vitro hemolysis (difficult draw, syringe aspiration, rough handling)	Pink plasma with a normal reticulocyte count; K⁺, LDH and AST rise in parallel
Spurious: cells shrink in the analyzer	Hyponatremia, underfilled EDTA tube	Low Na⁺ (MCHC can approach 40 g/dL); short-filled tube
True: free plasma Hb adds to measured Hb	Intravascular hemolysis: hemolytic transfusion reaction, mechanical heart valve, toxins or severe infection	Pink or red plasma, dark urine, falling Hb, high LDH, low haptoglobin
True: spherocytes keep Hb but lose membrane	Warm autoimmune hemolytic anemia (AIHA), hereditary spherocytosis (HS), ABO hemolytic disease of the newborn	Spherocytes on smear; direct antiglobulin test (DAT) positive in AIHA and ABO disease, negative in HS
True: dehydrated (dense) red cells	Sickle cell disease, HbSC disease, hereditary xerocytosis	Known hemoglobinopathy; MCHC can be well above 36 g/dL
True: heat-damaged cells	Severe burns	Very small cells and fragments after major burns

Pink plasma is not always a bad draw: Pink plasma can be the patient, not the tube. A high MCHC with pink plasma plus a falling Hb, dark urine, jaundice or reticulocytosis means the hemolysis is happening in the body. During or after a transfusion, think hemolytic transfusion reaction. With fever, shock and massive hemolysis, think severe sepsis or a toxic cause.

Low (hypochromia <32 g/dL)

Mechanism	Common causes	Bedside clue
Too little iron to build Hb	Iron deficiency (chronic GI or menstrual blood loss, pregnancy, poor intake, malabsorption)	Low MCV and MCH; pale cells with wide central pallor; low ferritin
Too little globin chain	Thalassemia trait and thalassemia disease	MCV very low for the degree of anemia; RBC count normal or high; MCHC often normal or only mildly low
Defective heme synthesis	Sideroblastic anemia (congenital or acquired)	Microcytic, hypochromic cells in many cases; ring sideroblasts on marrow
Spurious: cells swell in the analyzer, raising Hct	Glucose ≥600 mg/dL (often IV-line contamination), sample stored 1–4 days at room temperature, hypernatremia	High MCV with low MCHC; check glucose, Na⁺ and collection time
Spurious: small white cells counted as red cells	Extreme lymphocytosis or lymphoblasts (chronic or acute lymphoid leukemia)	Very high WBC; double population on the red cell histogram

MCHC is a weak iron test: A normal MCHC does not rule out iron deficiency. In an anemic patient, a ferritin below 45 ng/mL supports iron deficiency per the AGA 2020 guideline. Inflammation and CKD raise ferritin. That is why you add transferrin saturation.

Interpretation & Bedside Approach

Step-by-step approach

Is it real? Check the whole CBC. Hct should be about 3 × Hb (±3). A mismatch, an analyzer flag, or lipemic, icteric or pink plasma means the lab should correct and rerun. Nobody treats the number until then.
How sick is the patient? Tachycardia, hypotension, chest pain, dark urine, new jaundice or fever with a high MCHC points to active hemolysis. A stable patient with chronic hypochromia gets an outpatient workup.
Acute vs chronic and the trend: Pull up the prior CBCs. A sudden high MCHC after normal values favors artifact or new hemolysis. A recent transfusion mixes donor and patient cells.
Read it with the other indices: MCV (size), MCH (Hb per cell), RDW (size variation) and the reticulocyte count. Use the pattern table below.
Classify: A low MCHC goes to iron studies (ferritin, transferrin saturation). If iron is normal, it goes to thalassemia testing. A confirmed high MCHC goes to smear review, reticulocytes, LDH, indirect bilirubin, haptoglobin and DAT.
Escalate or dispose: A suspected hemolytic transfusion reaction or massive hemolysis is an emergency. Iron deficiency anemia in men and postmenopausal women needs a GI evaluation. AGA 2020 recommends bidirectional endoscopy.

Patterns with the other indices

Pattern	MCV	MCHC	Suggests
Microcytic, hypochromic	↓	↓	Iron deficiency; thalassemia if the RBC count is high
Microcytic, MCHC normal	↓	N	Thalassemia trait; check ferritin and RBC count
Normocytic, normochromic	N	N	Acute blood loss, CKD, anemia of inflammation
Macrocytic	↑	N	B12 or folate deficiency, liver disease, alcohol
High MCV, high MCHC, low RBC count	↑	↑	Cold agglutinins: warm the sample and rerun
High MCV, low MCHC	↑	↓	Glucose contamination, old sample or hypernatremia (artifact)
High MCHC, high RDW, spherocytes	N or ↓	↑	Hereditary spherocytosis or AIHA: send a DAT

Spherocytes on the smear: immune or hereditary?

DAT positive: warm AIHA, a delayed hemolytic transfusion reaction, or in a newborn, ABO hemolytic disease.
DAT negative: hereditary spherocytosis is likely. Per the British Society for Haematology (BSH) guideline, spherocytes, a raised MCHC, reticulocytosis and a family history need no further tests. If the picture is equivocal, the screening tests are eosin-5′-maleimide (EMA) binding or cryohemolysis.

Iron deficiency smear: small pale red cells with thin pink rims and wide central pallor — **Figure 1:** Low MCHC (hypochromia): severe iron deficiency, MCV 55 fL. Red cells are small and pale with only a thin rim of hemoglobin; the lymphocyte gives scale. Source: Wikimedia Commons, Ed Uthman, CC BY 2.0

Hereditary spherocytosis smear: many small, dense, round red cells with little or no central pallor — **Figure 2:** High MCHC (spherocytes): hereditary spherocytosis. Many cells are small, round and dense, with reduced or absent central pallor, because membrane is lost while hemoglobin is kept. Source: Wikimedia Commons, Paulo Henrique Orlandi Mourao, CC BY-SA 3.0

Special Populations

Population	What changes	Clinical implication
Neonates & infants	Mean about 34 g/dL regardless of gestational age; somewhat higher values can occur in healthy neonates; heel-stick samples can read higher	In a jaundiced newborn, MCHC ≥36 g/dL raises suspicion of HS but is not diagnostic; check the DAT and smear, and if equivocal use EMA binding or cryohemolysis
Children & adolescents	Similar to adult	HS often presents with anemia, jaundice, splenomegaly or gallstones; a negative family history does not exclude it (recessive and new mutations)
Pregnancy	No clinically meaningful difference	Low MCHC with low MCV: check ferritin; iron deficiency is common
Older adults	No clinically meaningful difference	New iron deficiency anemia: look for GI blood loss
CKD / dialysis	Anemia is usually normochromic	Ferritin is less reliable; add transferrin saturation before calling iron status
Sickle cell and HbSC disease	Dense, dehydrated cells raise MCHC, sometimes well above the usual range	Expected in these patients once interference is excluded; compare with the patient's baseline
Recently transfused	Indices reflect a mix of donor and patient cells	Use the pre-transfusion CBC for an HS or iron workup

Interfering Factors & Pitfalls

Collection & handling

Factor	Effect	Why	Avoid / fix
In vitro hemolysis	↑	Lysed cells lower RBC count and Hct while their Hb is still measured	Redraw with good technique; avoid forceful syringe transfer
Underfilled EDTA tube	↑	Excess EDTA shrinks red cells	Fill to the line
Draw above a dextrose infusion	↓	Glucose-loaded cells swell in the diluent: falsely high MCV and Hct	Draw from the other arm, or follow line-draw discard policy
Lipid infusion running	↑	Lipid turbidity raises measured Hb	Draw away from the infusion; lab can replace plasma
Delay at room temperature (1–4 days)	↓	Red cells swell with storage	Analyze promptly or recollect
Capillary sample (neonates)	↑	Hemoconcentration and lower MCV	Confirm an abnormal value on a venous sample

Physiologic / biologic

Factor	Effect	Why	Avoid / fix
Cold agglutinins	↑ (with ↑ MCV, ↓ RBC)	Clumps count as one cell or are excluded	Warm to 37 °C for 10–30 min and rerun; for high titers, keep a new tube at 37 °C until analysis
Lipemia, icterus, IgM paraprotein, cryoglobulins	↑	Turbidity or color falsely raises Hb	Plasma replacement, dilution or optical Hb
Hyponatremia	↑	Cells shrink in the higher-osmolality diluent	Interpret with Na⁺; cannot be corrected in the lab
Hypernatremia or glucose ≥600 mg/dL	↓	Cells swell in the diluent	Spun (micro) Hct and recalculate
Hyperleukocytosis	↑ or ↓	Large granular cells raise Hb (↑); small lymphoid cells are counted as red cells (↓)	Dilution or optical counts

Assay & device-specific

Factor	Effect	Why	Avoid / fix
Impedance analyzers	False + or False −	MCHC is always calculated (Hb ÷ Hct), so any Hb or Hct error lands in it	Labs use an out-of-range MCHC as a validation check
Lysis-resistant HbS or HbC cells	↑	Unlysed cells add turbidity to the Hb reading	Longer lysis or dilution and rerun

Common misinterpretations

“MCHC above 37 is impossible”: Wrong. Real values can run past the usual range in HS, sickle cell and HbSC disease. Extreme values still need a check for interference.
A normal MCHC rules out iron deficiency: It doesn't. Check ferritin.
High MCHC on a pink sample is always a bad draw: Not always. Intravascular hemolysis in the body raises MCHC too.
Thalassemia always lowers MCHC: No. Thalassemia trait usually has a normal or near-normal MCHC.

Do not chase a number the lab has flagged: A normal smear with a high MCHC is usually artifact. Put the hemolysis or spherocytosis workup on hold. Have the lab warm, dilute or replace the plasma, then rerun it.

Physiology & Test Basics

What it measures

MCHC is the average hemoglobin concentration inside a red cell. It tells you how densely the cell is packed. Its siblings measure cell size (MCV), hemoglobin mass per cell (MCH) and size variation (RDW). Low MCHC means pale, under-filled cells (hypochromia). High MCHC means dense cells, like spherocytes or dehydrated cells, or a measurement error.

Index	Measures	Units	Think of it as
MCV	Cell volume	fL	How big is the cell?
MCH	Hb mass per cell	pg	How much Hb is in the cell?
MCHC	Hb concentration in cells	g/dL	How densely packed is the Hb?
RDW	Variation in cell size	%	How uneven are the cells?

Physiology & regulation

Hb supply: Run short of iron, globin chains or heme and MCHC falls.
Cell water: Cation content sets how much water a red cell holds (Na⁺/K⁺ pump, PIEZO1 and Gardos channels, K⁺–Cl⁻ cotransport). Lose K⁺ and water, and the cell dehydrates and MCHC rises (sickle cell, xerocytosis).
Membrane loss: Spherocytes lose surface area but keep their Hb. The concentration rises.
Narrow range: MCHC barely varies between healthy people. That is why labs use it to catch analyzer interference.

How it is measured

Draw it in a lavender-top (K₂EDTA) tube, fill it to the line and invert it gently. No fasting is needed. Every automated CBC reports MCHC. Impedance analyzers measure Hb by spectrophotometry after lysis, count and size the red cells, then calculate MCHC = Hb ÷ Hct. Optical analyzers can also derive cellular Hb concentration directly. The reference method divides spectrophotometric Hb by a spun Hct.

Why it matters

MCHC points you toward iron deficiency when it is low. It points toward spherocytes and hemolysis when it is high. It is also often the first clue that the CBC is unreliable. In the ED, ICU or on transport, a sudden high MCHC with pink plasma can be the earliest lab sign of a hemolytic transfusion reaction or massive hemolysis.

Clinical Pearls

Rule of three: Hct should be about 3 × Hb (±3) when cells are normal in size and color. Off that range, the MCHC is off too. Suspect lipemia, clumping or hemolysis before you suspect disease.

Nursing: draw away from infusions: Draw above running dextrose and the CBC can show a high MCV with a low MCHC. Draw during a lipid infusion and Hb and MCHC can read falsely high. Use the other arm or follow your line-draw discard policy.

Transport: keep cold-agglutinin samples warm: A patient with known cold agglutinins needs a plan before the tube leaves. Ask the lab how to handle it. High-titer samples may need to stay at 37 °C from draw to analysis.

Pink plasma: tube or patient?: Hemolysis in the tube gives pink plasma with a normal reticulocyte count. K⁺, LDH and AST rise in step. Hemolysis in the body brings reticulocytosis and low haptoglobin, and often dark urine.

Spherocytes plus high MCHC: Send a DAT. A positive result points to immune hemolysis: warm AIHA, transfusion reaction, or ABO disease in newborns. A negative result points to hereditary spherocytosis.

Jaundiced newborn: An MCHC ≥36 g/dL with hyperbilirubinemia makes you think of HS. Look further with a DAT, smear review and family history. That number alone does not diagnose it. Use the lab's neonatal interval.

Transfusion reaction: MCHC jumps with pink plasma, fever, back pain or dark urine during or after a transfusion? Stop the transfusion. Keep the line open and follow your transfusion-reaction protocol.

References

Girard, S., Berda-Haddad, Y., Brouzes, C., et al. (2025). Breaking free from MCHC interferences? French-speaking Cellular Haematology Group (GFHC) review of causes, rising trends and practical solutions. International Journal of Laboratory Hematology, 47(5), 798–807. https://doi.org/10.1111/ijlh.14536
Gulati, G., Uppal, G., & Gong, J. (2022). Unreliable automated complete blood count results: Causes, recognition, and resolution. Annals of Laboratory Medicine, 42(5), 515–530. https://doi.org/10.3343/alm.2022.42.5.515
Bolton-Maggs, P. H. B., Langer, J. C., Iolascon, A., Tittensor, P., & King, M.-J. (2012). Guidelines for the diagnosis and management of hereditary spherocytosis: 2011 update (current BSH guideline). British Journal of Haematology, 156(1), 37–49. https://doi.org/10.1111/j.1365-2141.2011.08921.x
Achenjang, N.-S., Jadczak, E., Ryan, R. M., & Nock, M. L. (2025). Hereditary spherocytosis: Review of presentation at birth. Children, 12(9), 1207. https://doi.org/10.3390/children12091207
Ko, C. W., Siddique, S. M., Patel, A., et al. (2020). AGA clinical practice guidelines on the gastrointestinal evaluation of iron deficiency anemia. Gastroenterology, 159(3), 1085–1094. https://doi.org/10.1053/j.gastro.2020.06.046
MedlinePlus, U.S. National Library of Medicine. (2026). RBC indices (normal values). https://medlineplus.gov/ency/article/003648.htm

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MCHC (Mean Corpuscular Hemoglobin Concentration)