MCHC Blood Test: What High and Low Results Mean, and What They Mean for Athletes

Key Takeaways

• MCHC is hemoglobin divided by hematocrit: the average concentration of hemoglobin inside your red cells.
• A very high MCHC is often a laboratory artefact rather than disease, so an isolated high result is best read with the rest of the blood count and the laboratory’s flags.
• In my clinical experience, an abnormal MCHC is often an incidental finding, and an explanation can often be found elsewhere in the same blood count. It is best interpreted with your own doctor.
• In red cell diseases such as hereditary spherocytosis and sickle cell disease, a genuinely high MCHC can reflect dehydrated red cells.
• In a cross-sectional study of adolescent female athletes, reticulocyte indices differed in the earliest stage of iron deficiency and MCHC only in the next stage, so a normal MCHC does not rule out low iron.
• In a study of highly trained male athletes, hard exercise raised hemoglobin and hematocrit but left MCHC unchanged, while the evidence on whether training changes resting MCHC is limited and inconsistent.
• In my view, athlete status alone is not necessarily a reason to test more often than in the general population. An annual basic check is a reasonable approach for many athletes, with closer follow-up for those prone to iron deficiency, such as athletes who menstruate.

Introduction

MCHC is the red cell index most people skim past on a complete blood count. When it is flagged high, the first suspect is often the sample rather than the patient: haematology laboratories commonly use MCHC as an analytical control, because a high value tends to point to an artefact.[1] In one laboratory study of 128 patients whose MCHC exceeded 365 g/L, 22 had red cell agglutination, 17 had optical interference, 18 had a red cell disease, and 71 fell into an “other” group.[2]

That makes the MCHC blood test unusual. It is less an early-warning marker than a consistency check, and for athletes, whose hemoglobin and hematocrit move with training, hydration and plasma volume, a ratio that stays steady is exactly what makes it useful.

As both a physician and former competitive athlete, I will walk through what the test measures, what high and low results usually mean, and how to read MCHC when the person on the report trains hard.

From a clinical perspective, MCHC is a calculated laboratory value that is reported automatically as one of the red cell parameters on a complete blood count. In my clinical experience in Finland, a complete blood count is often ordered when patients have laboratory tests taken at all, although in some situations an inflammation marker may be ordered instead. Because the test is ordered so often, an MCHC outside the reference interval turns up from time to time, and patients often worry about it and look up what it means.

What Does an MCHC Blood Test Measure?

MCHC stands for mean corpuscular hemoglobin concentration. In the reference method, hemoglobin is measured by spectrophotometry, hematocrit by centrifugation, and MCHC is calculated as hemoglobin divided by hematocrit.[1] Depending on the analyser, MCHC is either measured directly or calculated; on impedance-based analysers it is always calculated from hematocrit and hemoglobin.[1]

Three red cell indices are easy to mix up:

• MCV: the average volume of the red cells
• MCH: hemoglobin divided by the red cell count, i.e. the average amount of hemoglobin per cell[1]
• MCHC: hemoglobin divided by hematocrit, i.e. how densely that hemoglobin is packed into the cell volume[1]

Results are reported in g/L or in g/dL depending on the laboratory; 340 g/L equals 34.0 g/dL. The average MCHC is around 340 ± 10 g/L, and the French-speaking Cellular Haematology Group (GFHC) notes that this is similar in full-term infants, premature infants and adults.[1] Because the method varies by analyser, compare your result with the reference interval printed on your own report.

Why a High MCHC Blood Test Result Is Often an Artefact

Because an MCHC blood test result is a ratio, anything that inflates the measured hemoglobin, or deflates the measured red cell count or cell volume, pushes it up. The GFHC review sorts the interferences into exactly those three mechanisms: overestimated hemoglobin, underestimated red cell count, and underestimated MCV.[1] The main culprits are:

• Cloudy or coloured plasma. Lipemic, icteric or hemolysed plasma can lead to overestimated hemoglobin and a falsely elevated MCHC, for example with severe hypertriglyceridemia (interference is typically seen above 20 g/L) or bilirubin above 250–300 mg/L.[1]
• Red cells destroyed in the tube. Excessive agitation, a difficult blood draw or syringe aspiration can break red cells in vitro, falsely raising MCHC; a new sample is then needed.[1]
• Underfilled tubes. Excess EDTA shrinks red cells and increases MCHC.[1]
• Agglutinins. Clumped red cells are undercounted, which falsely raises MCHC. With cold agglutinins the anomalies often disappear after warming the sample to 37°C for 30 minutes; warm agglutinins do not correct this way.[1]
• Low blood sodium. Hyponatremia can produce MCHC values above 365 g/L, sometimes approaching 400 g/L, because red cells adapted to low plasma osmolality dehydrate rapidly in the analyser’s higher-osmolality medium.[1]

Modern analysers help. In the Marseille study above, switching to optical red cell and hemoglobin measurements corrected the abnormal results in 36 of 39 patients with agglutination or optical interference, and a score built from reticulocyte parameters identified 17 of the 18 patients with a red cell disease.[2]

When a High MCHC Is Real

A genuinely high MCHC blood test result can reflect dehydrated red cells. In red cell diseases, MCHC is frequently increased, sometimes above 380 g/L, mainly because of dehydration at the cellular level rather than pre-analytical problems; the GFHC names sickle cell disease, HbSC disease and hereditary spherocytosis as typical examples.[1]

Hereditary spherocytosis is the most common inherited red cell membrane disorder in Northern Europe and North America, diagnosed in 1 in every 2,000 individuals, and mild forms may be asymptomatic.[3] Diagnosed late, it carries a risk of gallstones and severe anemia.[3] MCHC and RDW were the first laboratory screening tests for the condition, and both indices are elevated during its course, although not necessarily in every patient.[3]

A study from a Buenos Aires paediatric hospital compared 94 patients with hereditary spherocytosis against 94 age-matched healthy children. MCHC averaged 35.67 ± 1.33 g/dL in patients versus 33.48 ± 0.68 g/dL in controls. Using an MCHC cut-off of 34.5 g/dL or above alone gave 86.17% sensitivity and 90.43% specificity, while combining it with an RDW cut-off of 14.5% gave 81% sensitivity and 98.9% specificity.[4]

Note that this 34.5 g/dL cut-off is close to the average MCHC of around 340 g/L (34 g/dL) mentioned earlier. Of the screening tests, the eosin-5′-maleimide (EMA) binding assay is the most specific for hereditary spherocytosis.[3]

Low MCHC and Iron Deficiency

A low MCHC blood test result means hypochromic red cells: less hemoglobin packed into each unit of cell volume. Iron deficiency is one cause to consider in athletes, but in the study below MCHC was not an early marker.

In a study of 219 adolescent female athletes aged 15–20 from seven sports, those in the earliest stage of iron deficiency (ferritin below 30 ng/mL) showed changes mainly in reticulocyte indices such as CHr and CHCMr. Significant changes in mature red cell indices, including hemoglobin, MCH and MCHC, were reported in the next stage, latent iron deficiency, and the authors state that microcytosis appeared later.[5]

In adults with iron deficiency anemia, a low MCH may be more common than a low MCV. In a hospital dataset of 2,503 patients with confirmed iron deficiency, 1,733 had iron deficiency anemia; among them, MCH was 28 pg or lower in 88.2%, but MCV was 80 fL or lower in only 52.9%.[6] That analysis did not report MCHC.

In practice, if MCHC is low together with low hemoglobin and a low MCV, I usually suspect iron deficiency anemia or a similar condition. I may then order ferritin, which, interpreted alongside the clinical picture, can help confirm the iron deficiency. From a clinical perspective, it is also worth clarifying why the iron is low, including whether the patient has a source of bleeding somewhere.

Causes, symptoms and treatment of a low result are covered in detail in my separate article on a low MCHC blood test.

What an MCHC Blood Test Means for Athletes

Hard exercise moves hemoglobin and hematocrit, not MCHC

Researchers sampled blood at every 3-minute stage from 39 highly trained male athletes (13 futsal players, 12 sprinters and 14 triathletes) during an incremental treadmill test to exhaustion. Red cell count, hemoglobin and hematocrit rose progressively, with hematocrit peaking 8.8%, 8.5% and 5.9% above resting values in futsal players, triathletes and sprinters respectively, and all three returned to resting values within the 30-minute recovery period. MCV, MCH, MCHC and RDW showed no significant changes during exercise or recovery.[7]

In practice, a sample drawn during or right after a hard session may therefore show higher hemoglobin and hematocrit while the MCHC blood test result stays about the same.[7]

Sports anemia is a plasma volume effect

Endurance-trained athletes often have a lower hematocrit, sometimes called “sports anemia.” This is not anemia in a clinical sense: these athletes actually have a larger total red cell mass and more hemoglobin than sedentary people, and the slight hematocrit drop is attributed to an increase in plasma volume.[8]

The same review discusses a decreased MCHC separately, as an indicator of a younger red cell population (see below).[8]

Younger red cells: the evidence on MCHC is mixed

Training also changes the age profile of circulating red cells. Exercise destroys mainly senescent red cells through intravascular hemolysis, from mechanical rupture in the capillaries of contracting muscle and from compression, for example in the soles of the feet during running or the palms of weightlifters. A 2013 review concludes that these adjustments lower the average age of circulating red cells in trained athletes, and it lists decreased MCHC and lower red cell density among the indicators of a younger red cell population.[8]

In my clinical experience, I interpret RDW, which reflects variation in red cell size, alongside the other blood count indices and, where appropriate, the reticulocyte count.

Direct comparisons are limited and inconsistent. In 79 amateur athletes (62 men and 17 women) training several times a week, the abstract reports higher MCV and MCHC than in healthy untrained volunteers, which the authors consider likely related to more circulating young red cells; the results section of the same paper, however, reports increased MCV and MCH with no change in MCHC. Within the same group, those above the median VO₂max had lower MCH and MCHC.[9]

Taken together, these sources do not show clearly whether training itself raises or lowers resting MCHC, so small within-range differences in athletes are hard to attribute to training.[8][9]

Iron deficiency: earlier markers than MCHC

Iron deficiency was common in the study of 219 adolescent female athletes: 60% had iron deficiency without anemia (45% in stage I and 15% in stage II).[5] A systematic review of 23 studies comprising 669 high-level female athletes aged 13–47 from 16 sports reported a 3–4% reduction in endurance performance associated with iron deficiency (ferritin below 40 µg/L); the included studies differed in design, so this should not be read as the expected effect in every athlete.[10]

Because this was a cross-sectional comparison of groups, it does not show the order of change within one athlete. Still, MCHC differed only in the more advanced group, so a normal MCHC blood test does not rule out low iron stores. In that study, low ferritin and abnormal reticulocyte hemoglobin indices identified iron deficiency in the earliest stage, when MCHC did not yet differ.[5]

In my clinical experience, athletes are often more sensitive than sedentary people to a drop in performance, sluggishness or a plateau, and understandably they worry when their results stop improving. Fatigue and exhaustion frequently appear at the same time, which makes the picture diagnostically difficult: overtraining may be involved, and depression can sometimes lie in the background. From a clinical perspective, laboratory tests are a reasonable part of the work-up, and ferritin is often the first one considered; athletes often ask for it themselves. I usually tell them that ferritin is worth checking together with the complete blood count, and in many situations thyroid tests as well, because hypothyroidism can resemble the same picture. In occupational health I see the same pattern in sedentary people, for whom ferritin has become a fashionable test for explaining exhaustion. Exhaustion is multifactorial, a careful differential diagnosis is warranted, and blood test results alone rarely explain it. In my experience, many of these patients turn out to have a moderate ferritin level.

When iron deficiency is confirmed, the treatment evidence below concerns ferritin and performance. The same systematic review reported improved endurance outcomes in iron-deficient female athletes with about 100 mg of oral elemental iron daily for up to 56 days, and with parenteral iron given every other day over 8–10 days; the two regimens are not interchangeable.[10] A meta-analysis of 13 randomised controlled trials with 449 participants found that oral iron significantly increased serum ferritin, while the rise in hemoglobin was not statistically significant. Ferritin increases were evident in athletes whose pre-supplementation ferritin was 12 µg/L or lower, effective doses ranged from 16 to 100 mg of elemental iron daily over 6–8 weeks, and the shorter protocols included did not show the same benefit.[11]

In my clinical experience, I do not necessarily recommend blood tests during the competitive season unless there is a reason for them. In my view, a reasonable approach for many athletes is an annual basic health check, much like for sedentary people, especially as they grow older. The situation is different for an athlete who menstruates and is prone to iron deficiency, where testing may need to be more frequent depending on the clinical picture. From a clinical perspective, athlete status alone is not necessarily an indication for more frequent testing than in the general population. It is also worth noting that, to my knowledge, there is no Finnish Current Care guideline specifically for athletes, so in practice sports medicine often relies on best practice rather than formal recommendations.

Blood-draw conditions that shift MCHC

• Finger-prick samples. Capillary blood can give different MCHC values than venous blood, and the direction of the difference may depend on the sampling conditions.[1] This is worth knowing if you use home test kits.
• Dehydration. In severe dehydration, MCHC is usually only moderately increased.[1] A markedly high MCHC blood test result is unlikely to be due to dehydration alone.
• Difficult draws and underfilled tubes. Both can falsely raise MCHC.[1]

How to Read Your MCHC Blood Test Result

In my clinical experience, I usually explain to patients that an MCHC value on its own does not necessarily mean anything specific. From a clinical perspective, MCHC needs to be interpreted together with the rest of the blood count, and it can be abnormal for many different reasons. In my clinical experience, an abnormal MCHC is often an incidental finding, and an explanation can often be found elsewhere in the patient’s blood tests. In iron deficiency anemia, for example, MCHC is often on the low side.

• Compare like with like. Use the reference interval on your own report, and compare against your own previous results from the same lab, drawn under the same conditions.
• Standardise the draw. Test rested and hydrated, from a vein and at a similar time of day. Where possible, avoid drawing during or straight after a hard session; in an incremental exercise study of highly trained male athletes, hemoglobin and hematocrit were temporarily raised.[7]
• Isolated high MCHC blood test result with everything else normal: ask whether the laboratory identified hemolysis, lipemia or another analytical interference. A new sample is needed when red cells were destroyed in vitro. Otherwise, whether to repeat the test or look further depends on how far the value is raised, the other results and the clinical situation.[1][2]
• High or high-normal MCHC with a high RDW: both indices are often elevated in hereditary spherocytosis, although normal values do not exclude it,[3][4] so it is worth asking your doctor whether testing for it makes sense, particularly if you also have anemia or gallstones.[3]
• Low MCHC: iron deficiency is one possible cause, so ferritin is often the next test, depending on the rest of the blood count and the clinical picture. Read the result alongside MCV, MCH and RDW. If iron studies are normal, other hypochromic causes need a clinician’s work-up.
• Normal MCHC but falling performance or unusual fatigue: ferritin may still be worth checking if the clinical picture suggests possible iron deficiency, because in the adolescent athlete study MCHC differed only at the more advanced stage.[5]
• MCHC alone is not enough to decide on iron. Supplementation raised ferritin in athletes whose pre-supplementation ferritin was 12 µg/L or lower.[11]

In my clinical experience, I would not encourage patients to interpret an MCHC result on their own or to look up its meaning online. This article describes what a result may reflect in general, but in practice it often cannot be interpreted without a doctor’s clinical experience and knowledge of what matters and what does not, and of what is common and what is likely in a given situation. From a clinical perspective, it is therefore worth asking your own doctor, who knows your situation, how to read the value and whether anything needs to be done at all or whether further assessment is warranted.

Conclusion

The MCHC blood test is best read as a ratio that normally stays steady. A high result can be an artefact: among 128 patients above 365 g/L, 39 had agglutination or optical interference and 18 had a red cell disease.[2] In red cell diseases such as hereditary spherocytosis, a genuinely high value can reflect dehydrated red cells.[1] In a cross-sectional study of adolescent female athletes, MCHC differed only in the more advanced stage of iron deficiency, while reticulocyte indices differed in the earliest stage.[5]

For athletes, the practical message is simple. In highly trained male athletes, hard exercise moved hemoglobin and hematocrit but not MCHC,[7] while in adolescent female athletes MCHC differed in iron deficiency only at the more advanced stage, later than reticulocyte indices.[5] With iron deficiency associated with a reported 3–4% reduction in endurance performance in high-level female athletes,[10] ferritin is worth considering even when the MCHC blood test looks fine, if the clinical picture points to possible iron deficiency.

In my clinical experience, an abnormal MCHC is often an incidental finding, and the explanation can often be found elsewhere in the same blood count, for example in iron deficiency anemia. When an athlete is tired or performing below expectations, I usually look at ferritin together with the complete blood count, and often at thyroid tests as well, because exhaustion is multifactorial and a careful differential diagnosis is warranted. Because an MCHC value is rarely interpretable without clinical context, it is worth asking your own doctor, who knows your situation, whether anything needs to be done at all.

References

[1] https://doi.org/10.1111/ijlh.14536

[2] https://doi.org/10.1111/ijlh.12565

[3] https://doi.org/10.21037/atm.2018.07.35

[4] https://www.medicinabuenosaires.com/demo/revistas/vol67-07/n6-2/v67_6-2_p698_700_.pdf

[5] https://doi.org/10.5114/biolsport.2017.64584

[6] https://www.mp.pl/paim/issue/article/15714/

[7] https://doi.org/10.7717/peerj.17040

[8] https://doi.org/10.3389/fphys.2013.00332

[9] https://www.mdpi.com/2077-0383/13/1/151

[10] https://doi.org/10.1016/j.jshs.2024.101009

[11] https://doi.org/10.1007/s40279-024-01992-8

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An MCHC blood test shows how concentrated hemoglobin is in your red cells. Learn what high or low results mean and how athletes should read them.