What Is MCH in Blood Test? Meaning, Low and High Values, and What It Means for Athletes

Key Takeaways: What Is MCH in Blood Test

In a blood test, MCH is the average amount of hemoglobin in one red blood cell. It is calculated from hemoglobin and the red cell count and is routinely reported as part of a standard complete blood count.
MCH on its own rarely leads to any action. An important first question is whether the patient is anemic, but MCH should also be read alongside the other red cell indices, even when hemoglobin is normal.
In clinical practice, results just outside the reference range are common and often not a cause for concern. Some people have small red cells, with low MCV and MCH but normal hemoglobin and a high red cell count, a pattern that can fit thalassemia trait.
Iron deficiency is, in Dr. Rintanen’s clinical experience, the most common cause of anemia. In iron deficiency anemia, hemoglobin and MCH are typically both low.
MCH falls late in iron deficiency. A normal MCH does not rule out low iron stores, so ferritin is the first-line test when iron deficiency is suspected.
A high MCH usually travels with a high MCV. In megaloblastic anemia from B12 or folate deficiency, MCH is typically elevated, but the patient remains anemic, so a high MCH is not reassuring.
Athletes’ performance may decline at ferritin levels considered “normal” in sedentary people, but iron is not a performance enhancer beyond correcting a deficiency. The aim is to correct a deficiency, not to optimize iron beyond it.

Introduction: What Is MCH in a Blood Test?

MCH is one of the quiet numbers on a complete blood count. Most people scroll past it on the way to hemoglobin. That is a mistake, because in iron deficiency anemia a low MCH can turn up more often than the better-known marker of small red cells. In a hospital dataset of 1,733 adults with iron deficiency anemia, 88.2% had an MCH of 28 pg or lower, while only 52.9% had an MCV of 80 fL or lower.[1]

For athletes the picture has another layer. Iron deficiency is common in sport, endurance training can expand plasma volume, and MCH changes only after iron stores have already fallen.[3]

This guide explains what MCH in a blood test measures, what low and high values usually point to, how MCH relates to MCV and MCHC, and how athletes should interpret it.

What Is MCH in a Blood Test?

MCH stands for mean corpuscular hemoglobin. It is the average amount of hemoglobin inside one red blood cell, reported in picograms (pg).[1]

MCH is not measured directly. Commonly used automated hematology analyzers measure the red blood cell count, hematocrit and hemoglobin, and then calculate MCH by dividing hemoglobin by the red cell count (and MCV by dividing hematocrit by the red cell count).[1] These red cell indices trace back to Wintrobe’s classification of anemia and are still derived from the same three measured values.[2]

In plain terms: hemoglobin tells you how much oxygen-carrying protein is in a given volume of blood, while MCH tells you how well stocked each individual red cell is.

MCH comes automatically as part of the complete blood count (CBC). In my clinical experience, a CBC is taken from almost every patient who has laboratory tests at all. Perhaps the main exception is a quick urgent-care or emergency visit where only an inflammatory marker is checked. In practice, this means MCH appears on a very large number of lab reports, even when nobody specifically ordered it, and it can be a useful piece of the overall assessment.

What Is a Normal MCH Level?

Reference intervals for the MCH blood test vary between laboratories and analyzers, so always read your result against the range printed on your own report.

Most patients recognize hemoglobin, but MCH is usually unfamiliar to them. In my clinical experience, patients often ask about it when one of the calculated red cell indices falls outside the reference range. This is fairly common and often not a cause for concern. A blood count reports many values, and reference intervals are statistical, so some people will have one or more results just outside them.

That said, two cut-offs come up repeatedly in the literature. Note that these are diagnostic and screening cut-offs used in research and guidelines, not laboratory reference intervals:

28 pg. The Swiss Society of Sports Medicine consensus uses 28 pg as the lower limit of normal for MCH in adults when staging iron deficiency.[3]
27 pg. In thalassemia carrier screening, an MCH below 27 pg is used as a trigger for further testing in several screening programs. In a Hong Kong analysis of a Chinese population, with concurrent iron deficiency excluded, an MCV cut-off of 80 fL or an MCH cut-off of 27 pg detected all heterozygous carriers of the SEA α-thalassemia deletion and of the β-thalassemia alleles common in that locality.[4]

For context in a trained population: in 931 elite male athletes, the 659 with normal iron status had a mean MCH of 29.9 pg.[9]

Low MCH in a Blood Test: What It Usually Means

A low MCH in a blood test means the average red cell carries less hemoglobin than expected. This finding often accompanies hypochromia, although MCH and MCHC measure different aspects of red cell hemoglobin. Two important explanations are iron deficiency and an inherited hemoglobin disorder such as thalassemia trait.

Iron deficiency

Iron is needed to build hemoglobin, so when iron supply to the bone marrow falls, new red cells come out under-filled. The Swiss consensus describes this as a stepwise process:[3]

Non-anaemic iron deficiency. Iron stores fall and ferritin drops, but hemoglobin, MCV and MCH are still normal.
Iron deficiency with microcytosis and/or hypochromia. If the negative iron balance continues, the youngest red cells are poorly hemoglobinized. MCH and MCV can then fall below their lower limits (28 pg and 80 fL) while hemoglobin itself is still in the normal range.
Iron deficiency anaemia. Finally, hemoglobin drops below normal.

The key point is that MCH falls in the middle of this sequence, not at the start. A normal MCH does not rule out low iron stores.

The same pattern held before anemia developed. In the same Hungarian hospital dataset, among 770 patients with iron deficiency but no anemia, 60.1% had an MCH of 28 pg or lower compared with 27.1% who had an MCV of 80 fL or lower.[1]

In my clinical experience, iron deficiency is the most common cause of anemia. In iron deficiency anemia, hemoglobin and MCH are typically both low, and MCV is often low as well when the anemia is microcytic. In my practice, these patients are usually prescribed oral iron first. Intravenous iron may be considered when a patient responds unusually poorly to oral iron and both hemoglobin and ferritin stay persistently low, but in my experience this is the exception rather than the rule.

Outside sport, in ordinary sedentary patients, iron deficiency is often accompanied by tiredness and exhaustion, which makes this a diagnostically difficult group. Many people are exhausted for other reasons, and some have low ferritin, or even ferritin within the reference range, without any anemia. In my clinical experience, their fatigue may not be caused by iron at all, yet some of them want or even demand iron infusions, and sometimes they receive them. In my view, low iron has become something of a fashionable explanation for fatigue. Athletes are a different situation, as discussed below.

Thalassemia trait

Low red cell indices are not always caused by iron deficiency. In the Hong Kong study, thalassemia carriers were identified by low MCV or MCH even though iron deficiency had been excluded, and the British haematology guidance cited there recommends testing for β-thalassemia trait when MCH is below 27 pg.[4]

In practice, I see some patients whose red cells are simply small: MCV and MCH are low even though hemoglobin is normal. In these patients, the red blood cell count is typically high. In my clinical experience, this pattern can reflect an inherited hemoglobin disorder such as thalassemia trait, particularly when iron deficiency has been excluded. Other hemoglobin disorders, such as sickle cell anemia, are a separate situation. In my practice in Finland it is relatively uncommon, but I do occasionally see patients with it, particularly in certain ethnic groups.

High MCH in a Blood Test: What It Usually Means

A high MCH in a blood test usually travels with a high MCV. Most reports of elevated MCV are accompanied by an elevated MCH, and a rise in either suggests macrocytosis, meaning larger-than-normal red cells.[6] Macrocytic anemia is defined as an MCV above 100 fL.[2]

Common causes of macrocytosis include:[5]

vitamin B12 deficiency
folate deficiency
alcoholism, with or without liver disease
liver disease
hypothyroidism
certain medications
reticulocytosis (a surge of young red cells, which are larger than mature cells)
bone marrow disorders, such as myelodysplastic syndromes

Vitamin B12 deficiency can result from insufficient dietary intake, for example in vegetarians, as well as from absorption problems such as pernicious anemia or gastric surgery.[2] Vitamin B12 deficiency may also be related to prolonged, strictly vegan diets.[6] Vitamin B12 deficiency does not necessarily lead to anemia and macrocytosis.[2] For a closer look, see our guide on B12 and folate in athletes.

In megaloblastic anemia, caused for example by folate or vitamin B12 deficiency, the red cells are large, so MCV and MCH are typically high, yet the patient is still anemic. In practice, a high MCH is therefore not reassuring in itself. In my clinical experience, macrocytosis, and sometimes megaloblastic anemia, can also be seen in people with heavy alcohol use. In alcohol-related macrocytosis, the elevated MCV may reflect the direct effect of alcohol, liver disease and/or folate deficiency.[5]

MCH vs MCV vs MCHC

On a blood test report, the three red cell indices answer slightly different questions:

Index	What it describes	What the cited data show in iron deficiency
MCV	Average red cell size	Below 80 fL in 52.9% of adults with iron deficiency anemia, vs 88.2% for MCH at or below 28 pg[1]
MCH	Average amount of hemoglobin per cell	Falls once newly formed red cells are under-hemoglobinized[3]
MCHC	Hemoglobin concentration in the cells	Poor discrimination of iron depletion (AUC 0.582) and limited discrimination of stage II iron deficiency (AUC 0.72) in male athletes[9]

The Swiss consensus considers MCV less useful than MCH in practice because MCV is less stable after the blood sample is taken.[3] Leaving a sample at room temperature for several hours can falsely raise the MCV.[5]

In practice, MCH on its own rarely leads to any action. It always needs to be interpreted against the rest of the blood count, and in my view the most important question is simply whether the patient is anemic or not. MCH can also stay within the reference range in a patient who is anemic: if the number of red cells falls, the average amount of hemoglobin in each remaining cell may still be normal.

When anemia is present, further anemia tests follow. In my practice, the first-line test is usually ferritin. Serum iron, transferrin, transferrin saturation and soluble transferrin receptor can be added, and haptoglobin may be checked when hemolysis is suspected. Reticulocytes, the young and slightly larger red cells, are often measured separately, and RDW may also change. Vitamin B12 and folate, which can also contribute to anemia, are standard tests in basic anemia panels as well.

If you want the details on the other two indices, see our guides on MCHC and MCV changes in athletes.

What the MCH Blood Test Means for Athletes

Iron deficiency is common in sport

A systematic review in the Journal of Sport and Health Science notes that up to 60% of female athletes experience iron deficiency. Including 23 studies with 669 high-level female athletes, it reported that iron deficiency negatively affected endurance performance by 3%–4% in the included studies.[7]

The figures depend heavily on the definitions used. In 219 female athletes aged 15–20, iron deficiency without anemia was found in 60%: 45% at stage I and 15% at stage II.[8] In 931 elite male athletes, 23.1% had iron deficiency, mostly early stage: 20.5% had iron depletion, 2.3% had iron-deficient erythropoiesis, and only 0.3% had iron deficiency anemia.[9]

Athletes are a different matter, however. In my view, an athlete’s performance may decline at ferritin levels that would be considered “normal” in a sedentary patient. Ferritin cut-offs are still debated: the Swiss consensus notes values ranging from 15 µg/l used by the World Health Organization upwards, and recommends 30 µg/l as a reasonable cut-off for adults, with 50 µg/l as the target before altitude training in elite sport.[3] The systematic review on female athletes above defined iron deficiency as a serum ferritin below 40 µg/L.[7]

That said, correcting low iron in an athlete is simply treating a deficiency. In my view, iron is not a performance enhancer beyond correcting a deficiency: once the deficiency has been corrected, there is no established additional benefit from extra iron, and there is no need to “optimize” iron levels beyond that. In my clinical practice, I follow the same general principles of diagnosing and treating iron deficiency in athletes as in other patients, while accounting for sports-specific iron demands, and athletic status alone is not an indication for intravenous iron. The main difference is that in athletes, iron deficiency may be corrected with oral iron at a lower threshold. The Swiss consensus likewise states that long-term daily oral iron intake or intravenous iron in the presence of normal or even high ferritin values does not make sense and may be harmful.[3]

MCH is a late marker, not an early warning

The findings from the athlete studies are consistent with the staging described above. In the 931 male athletes, mean MCH was 29.9 pg with normal iron status, 29.3 pg with iron depletion, and 27.4 pg with iron-deficient erythropoiesis.[9] The drop in the depletion group was statistically significant, but the average stayed above the 28 pg lower limit used in the Swiss consensus. At the second stage, which included only 21 athletes, MCH discriminated well: an optimal cut-off of 28.4 pg gave an area under the ROC curve of 0.924 for detecting iron-deficient erythropoiesis.[9]

The findings of the female athlete study were consistent with the same pattern across stages of iron deficiency. Early iron deficiency changed mainly reticulocyte indices. Mature red cell indices including MCH changed at the second stage, and the authors interpreted signs of small cells as appearing later still.[8]

There is also a timing issue. Reticulocyte hemoglobin (CHr or Ret-He) responds within 48–72 hours to a change in iron supply, whereas MCV and MCH react only over weeks.[3] The consensus also describes that when iron balance stays negative, the youngest red cells are the first to be insufficiently hemoglobinized, with a lower MCH than the cell population as a whole.[3] For earlier detection, see reticulocyte count in athletes and ferritin levels for athletes.

The practical message: in an athlete, a normal MCH blood test result does not clear iron status. A low MCH, on the other hand, suggests iron deficiency has already progressed past the store-depletion stage, or that another cause such as thalassemia trait needs to be considered.

Sports anemia vs true iron deficiency

Endurance training expands plasma volume. This can lower hemoglobin and hematocrit simply by dilution, a condition often called dilutional pseudoanaemia or sports anemia. According to the Swiss consensus, red cell mass is normal in this situation, ferritin, MCV and MCH stay within the normal range, and performance is not affected. The consensus cites an estimate that it can be observed in about 10–15% of mainly endurance athletes, especially when training time exceeds 10 hours per week.[3]

The male athlete data match this. In the 6.1% of athletes classified as having findings consistent with dilutional sports anemia (based on blood count criteria; plasma volume was not measured directly), only hemoglobin, hematocrit and red cell count were lower with a large effect size compared with athletes with normal iron status. The absolute reticulocyte count was also slightly lower, with a small effect. The authors note that these three values all depend on blood volume. MCH was not lower; it was slightly higher (30.5 vs 29.9 pg, a small effect).[9]

This is where MCH earns its place on an athlete’s blood test report. Low hemoglobin with a normal MCH and normal ferritin may be compatible with dilution, although it does not establish the diagnosis, whereas a low MCH fits the iron-deficient picture described above. One caveat: the consensus notes that dilutional pseudoanaemia cannot be ruled out by a venous blood examination alone, although serial measurements across the season are helpful in practice.[3] Our article on sports anemia covers this distinction in more depth.

Interpreting an MCH Blood Test Around Training

Ferritin, which is often measured alongside the blood count when an athlete’s iron status is assessed, behaves as an acute phase protein and can rise after hard training or illness. The Swiss consensus therefore advises excluding acute phase reactions, such as recent training sessions and infections (with CRP), before interpreting the results.[3] Sample handling matters too, since a delayed sample can distort the MCV.[5] Our guide on preparing for a blood test as an athlete goes through the practical steps.

Conclusion: What Is MCH in Blood Test

In a blood test, MCH tells you how much hemoglobin the average red blood cell carries. A low value usually raises the question of iron deficiency or thalassemia trait, and a high value usually travels with large red cells from causes such as B12 or folate deficiency, alcohol or liver disease.

In practice, MCH on its own rarely changes what happens next. In my view, the key question is whether the patient is anemic, and MCH is one clue to the cause. A result just outside the reference range is common and often not a cause for concern, while a high MCH is not reassuring in itself.

For athletes, MCH has two strengths and one weakness. It is not directly reduced by plasma-volume dilution alone, which can help separate findings compatible with sports anemia from real deficiency, and in a large hospital dataset of iron-deficient adults, MCH was at or below the study’s threshold more often than MCV was. But it falls late: a drop in MCH generally reflects a later stage of iron deficiency than the initial depletion of iron stores. Interpreting MCH together with ferritin and the rest of the blood count, and following it over time, gives a more complete picture of iron status than MCH alone. Remember, too, that iron is not a performance enhancer beyond correcting a deficiency. In my view, the goal is to correct a deficiency, not to push iron levels as high as possible.