MCH shows how much hemoglobin a single red blood cell contains on average. In effect it is the cell's "saturation" with the oxygen-carrying protein.
MCH goes hand in hand with MCV: small cells are usually also poor in hemoglobin (hypochromia), so both indices fall together — the classic picture of iron deficiency.
Reference ranges
The reference range depends on the lab; typical values for adults:
| Normal | 27 – 33 pg |
| Low (hypochromia) | iron deficiency, thalassemia |
| High (hyperchromia) | B12/folate deficiency, macrocytosis |
| Looked at with MCV | both low — iron deficiency |
What an elevated level means
High MCH (hyperchromia) usually accompanies macrocytosis: large red cells contain more hemoglobin. The causes are the same as for high MCV — a deficiency of vitamin B12 and folate, alcohol, liver disease.
What a low level means
Low MCH (hypochromia) — the cells have little hemoglobin. The most common cause is iron deficiency, when there is nothing to "fill" the red cells with. It also occurs with thalassemia and some anemias of chronic disease.
How the test is done
MCH is calculated automatically in the complete blood count and is interpreted only within the set of indices (MCV, MCH, RDW) together with hemoglobin and ferritin.
In practice a doctor relies primarily on MCV and RDW, and uses MCH as a confirming touch to the picture.
What affects the value
- Iron deficiency — lowers MCH (hypochromia).
- B12 and folate deficiency — raises MCH.
- Thalassemia — lowers MCH.
- Alcohol and liver disease — raise MCH.
- Technical factors (lipemia, high leukocytosis) — distort the calculation.
- Relationship with MCV — they usually change in concert.
Assess iron deficiency
Low MCH is a frequent companion of iron deficiency; assess the risk:
Frequently asked questions
How does MCH differ from MCV?
MCV is the size of a red blood cell, while MCH is how much hemoglobin it contains on average. With iron deficiency both usually fall: the cells become both small (low MCV) and pale (low MCH).
MCH is low — what does it mean?
Most often it is a sign of iron deficiency (hypochromia): the red cells have little hemoglobin. Low ferritin and transferrin saturation confirm the diagnosis. More rarely the cause is thalassemia.
Do I need to test MCH separately?
No. MCH is calculated automatically in the complete blood count and largely duplicates MCV in meaning. It is not ordered separately — the whole picture of the indices together with hemoglobin matters.
Related terms
Sources
- Red Cell Indices — Clinical Methods (NCBI)
- Normal and Abnormal CBC with Differential — StatPearls (NCBI)
- MedlinePlus (NIH) — RBC Indices