Mean Corpuscular Haemoglobin (MCH)
MCH is the average amount of haemoglobin — the part that carries oxygen — packed inside each red blood cell. Your GP reads it together with the size of your cells and the rest of your blood count to help work out the type and likely cause of anaemia, so a single off result is rarely read on its own.
Standard CareWhat is mean corpuscular haemoglobin (mch)?
MCH stands for Mean Corpuscular Haemoglobin. It is a calculation of the average amount of haemoglobin packed inside each of your red blood cells. Haemoglobin is the iron-rich protein that picks up oxygen in your lungs and carries it to the tissues all over your body, so MCH is, in effect, a measure of how much oxygen-carrying cargo each red cell is built with. MCH is reported in picograms (pg) — a picogram is a trillionth of a gram — and it appears automatically on every full blood count (FBC). It is never read in isolation: it sits within a group of red cell indices alongside MCV (mean cell volume — the average size of your red cells) and MCHC (mean cell haemoglobin concentration — how densely that haemoglobin is packed). Together these indices help your GP recognise the pattern of an anaemia and narrow down its cause. MCH tends to move in step with MCV: when red cells are small (microcytic), they usually carry less haemoglobin, so MCH is low; when they are large (macrocytic), MCH is often high. That is why the indices are always read as a set.
Why is it tested?
MCH adds useful detail to a haemoglobin result. Knowing haemoglobin is low is a starting point; knowing whether each red cell is carrying a normal or a reduced amount of haemoglobin helps point towards a cause. Red cell indices including MCH are used to investigate anaemia and vitamin deficiencies, bone marrow disorders, and liver disease. They help classify an anaemia so that any follow-up testing can be targeted rather than scattered. MCH is not usually ordered on its own — it is part of every standard full blood count. If your GP orders an FBC to look into tiredness, breathlessness, pale skin, or a known condition such as iron deficiency, MCH will be on the results.
Reference range (Australia)
Reference intervals for MCH are laboratory- and analyser-specific and vary slightly between pathology services. The range printed on your own report is the correct one for your result.
Reference intervals vary between laboratories. Always use the range printed on your own report.
What your result means
A low MCH means each red cell is carrying less haemoglobin than expected, a pattern usually seen with small, pale red cells. The most common cause is iron deficiency, because iron is needed to build haemoglobin. Thalassaemia — an inherited condition affecting haemoglobin production — can produce a similar picture. A low MCH on its own does not confirm a diagnosis. Your GP will look at it together with MCV, haemoglobin, ferritin, and iron studies to work out the likely cause and whether anything further is needed.
An MCH within the range on your report suggests your red cells are being built with a normal amount of haemoglobin. If haemoglobin is also normal, that is reassuring. If haemoglobin is low but MCH is normal, your GP will look at the other indices and your wider results to understand why. A normal MCH does not rule out anaemia — it helps describe its pattern.
A high MCH usually means your red cells are carrying more haemoglobin than average, which most often goes together with larger-than-usual red cells (macrocytosis). A common reason for that pattern is vitamin B12 or folate deficiency, where red cells are made larger and less efficiently. A mildly raised MCH on a single result is often not significant on its own. Your GP will read it alongside MCV, haemoglobin, and your other results before drawing any conclusions — it is worth raising at your next appointment rather than reading too much into one number.
What can affect your result
Iron availability is a major influence on MCH. Iron is central to the haemoglobin molecule, so when iron is in short supply, red cells are made with less haemoglobin and MCH falls. Ferritin (your iron-storage protein) and iron studies are the tests that pin this down. Vitamin B12 and folate matter too. Your body needs nutrients such as vitamin B12, folate, and iron to make red blood cells; a shortage of B12 or folate tends to produce larger cells that carry more haemoglobin each, nudging MCH up. Inherited conditions affecting haemoglobin, such as thalassaemia, can lower MCH independently of iron status. Because MCH is a calculated index, your GP always interprets it together with MCV, MCHC, haemoglobin, and — where relevant — iron studies, rather than on its own.
When to act
MCH is a supporting index rather than a standalone test. If your MCH is outside the range on your report, the most useful step is to look at it alongside haemoglobin, MCV, MCHC, ferritin, and iron studies — which is exactly what your GP will do. If haemoglobin is also low, a conversation with your GP is worthwhile so they can put the pattern together with your symptoms and history and decide whether further testing is warranted. If MCH is outside range but haemoglobin is normal and you feel well, it is still worth mentioning at your next visit, so your GP can decide whether it needs a follow-up count. This page is general information and is not a substitute for advice from your GP.
Frequently asked questions
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