MCHC blood value: more often a measurement error than a finding

Your MCHC blood value describes how concentrated the haemoglobin inside your red blood cells is, usually between 32 and 36 g/dl or 19 to 23 mmol/l. Unlike the rest of your blood count it is not measured but calculated.

That single property changes everything about how you should read this value.

MCHC is your haemoglobin divided by your haematocrit. If something is off with either of those two, your MCHC is the first number to go crooked. Labs therefore use it as an internal control: a high MCHC is a reason for the lab to look at the tube again, not to consider a diagnosis (PMID 34346820).

What is MCHC in the blood?

MCHC stands for mean corpuscular haemoglobin concentration, the average haemoglobin concentration per red blood cell. It does not describe how much haemoglobin a cell contains, but how densely that haemoglobin is packed into the cell's volume. Read it as the fill level of your red blood cells.

Compare it with your MCV, which describes cell size, and with MCH, which gives the amount of haemoglobin per cell.

MCHC combines those two. Which is also why it is so sensitive to an error in either.

How is the MCHC value calculated?

Your analyser measures three things directly: the number of red cells, their average volume and your total haemoglobin. Everything after that is arithmetic. MCHC comes from dividing your haemoglobin by your haematocrit, and your haematocrit is itself already calculated from cell count times cell volume.

So arithmetic stacks on arithmetic. Any error in the numerator or denominator comes back magnified in the result.

Imagine your haemoglobin is 9.3 mmol/l and your haematocrit 0.42, so your MCHC works out at 22.1 mmol/l, comfortably normal. If 5 percent of your red cells break on the way to the lab, your haematocrit falls to 0.40 while your measured haemoglobin stays the same, and your MCHC shifts to 23.3.

Nothing changed about your blood. Only about the tube.

Four common situations, the same outcome four times. That is why a high MCHC first raises a question about the sample at the lab.

What does a high MCHC value mean?

An MCHC above roughly 36 g/dl is close to physiologically impossible, because haemoglobin starts to crystallise at that concentration. Such a result therefore almost always points at interference in the sample. The literature describes cold agglutinins explicitly as a cause of an apparently raised MCHC (PMID 3969960).

The exception is spherocytosis, an inherited condition in which red cells are sphere-shaped and genuinely more densely filled. It sits at the top of every Dutch page, while in practice it is rare.

Modern labs have an automated check for this: if the MCHC crosses a threshold, the sample automatically goes back for review before the result is released (PMID 34346820).

So if you see an MCHC of 37 on your result with nothing else abnormal, ask for a repeat before you search any further.

What does a low MCHC value mean?

A low MCHC, called hypochromia, means your red blood cells are less densely filled with haemoglobin. This is a genuine finding and usually fits iron deficiency, often alongside a low MCV and a raised RDW. Unlike the high side, the low side is rarely an artefact.

In endurance athletes this pattern matters, because iron deficiency develops faster there than in non-athletes.

MCHC is the last of the three indices to fall, though. Your RDW blood value moves first, your MCV next, and your MCHC only once the deficiency has been running a while.

Which is why a normal MCHC is no proof that your iron is in order.

Does your training affect your MCHC?

Directly, barely. MCHC is a ratio, and ratios are insensitive to dilution: if training expands your plasma volume, your haemoglobin and haematocrit both fall and their quotient stays roughly the same. That makes this value unusually stable in a trained body.

Exactly the opposite holds for your albumin blood value, which does visibly fall through that same dilution.

Indirectly, training can play a part. Red cell breakdown during hard efforts releases free haemoglobin into your plasma, and that pushes a measured MCHC up without anything having changed about your cells.

So do not draw straight after a long run if you want to look at this value seriously.

When should you discuss an abnormal MCHC with your GP?

With a low MCHC alongside a low MCV, a low ferritin or symptoms of anaemia. And with a high MCHC that persists after a properly repeated draw, especially with jaundice, dark urine or a family history of anaemia.

Thuisarts describes an abnormal blood result as a reason to look further rather than a diagnosis, and the NHG guidelines apply the same pattern thinking to anaemia. RIVM points out that reference values differ per laboratory in blood testing, which matters extra for a calculated value like this one because labs use different units.

External quality assessment rounds show that the analytical performance of blood count parameters varies by concentration, which underlines the value of a repeat (PMID 31339849).

Where do you start?

Check whether your MCHC is abnormal on its own or together with your MCV and RDW. If it is the only one and it reads high, treat that as a sample question first and a medical question second. Repeat in a calm week, fasted, without hard training in the preceding 24 hours.

Our complete blood count test reports your red series including MCHC, with an assessment by a BIG-registered doctor.

How the indices connect is covered in complete blood count explained and in the complete biomarker guide for athletes. For the two values MCHC is derived from, read MCH blood value explained and high MCV explained.

References

1. Prospective validation of an automatic reflex test for identifying spurious elevations of mean corpuscular haemoglobin concentration due to the presence of cold agglutinins. Scandinavian Journal of Clinical and Laboratory Investigation. 2021. PMID 34346820.
2. Spurious red blood cell parameters due to serum cold agglutinins: observations on Ortho ELT-8 cell counter. American Journal of Clinical Pathology. 1985. PMID 3969960.
3. Molina A, Alcaraz J, Guiñón L, et al. Study of the analytical performance at different concentrations of hematological parameters using Spanish EQAS data. Clinical Chemistry and Laboratory Medicine. 2019. PMID 31339849.
4. RIVM. Blood testing and reference values. Accessed 2026.
5. NHG. Dutch College of General Practitioners, anaemia guideline. Accessed 2026.
6. Thuisarts. My blood result is abnormal. Accessed 2026.

Disclaimer

Every blood test result includes a professional assessment by a BIG-registered doctor. This article gives general information and is not a substitute for medical advice. For treatment decisions, discuss your results with your GP.