Understanding Blood Test Results

If you are suspected of having iron deficiency your doctor will ask you to have a blood test to check your full blood count and iron studies.

When looking at the full blood count the important indices to look at are:

  • Haemoglobin
  • MCV
  • Serum iron
  • Serum ferritin
  • Serum transferrin
  • Transferrin saturation


Your haemoglobin level will determine if you are anaemic. The reference ranges can differ from various laboratories but according to the WHO you are anaemic if it is less than 120g/L in women and 130 g/L in men. The ranges in pregnancy and children are slightly different (see table). The finding of anaemia in the context of iron deficiency indicates that the iron stores are severely depleted.

Table: WHO definition of anaemia according to age and sex 1

Age or Gender Group Haemoglobin (g/L)
Children 6 to 59 Months<110 g/L
Children 5 to 11 Years <115 g/L
Children 12 to 14 Years <120 g/L
Non-pregnant Females (≥ 15 Years) <120 g/L
Pregnant Females <110 g/L
Males (≥ 15 Years) <130 g/L

MCV (mean corpuscular volume)

This value represents the size of your red cells. In iron deficiency this value is often below normal.

MCHC (mean corpuscular haemoglobin concentration)

This value represents the average haemoglobin concentration in a single red cell. Once again, in iron deficiency this value is below normal.

The iron studies can be little more difficult to interpret, but in early stages of iron deficiency the full blood count is often normal, so these values are important.

Serum iron

This measures the amount of iron in your serum that is not bound to protein. The amount of iron in your serum does not correlate with how much iron there is in your body therefore it is never an indicator of the iron status.

Serum ferritin

This is a protein to which iron is bound. It indicates the amount of iron in your stores and therefore when this level is low (less than 30 mcg/L) it is diagnostic of iron deficiency. Because the serum ferritin can also rise when there is any inflammatory activity in your body a normal or high level does not necessarily exclude iron deficiency. Therefore, a low level is diagnostic of iron deficiency and a normal or even high level may still signify iron deficiency if there is inflammatory activity.

Serum transferrin

This is the protein that transports iron around your body. The iron is usually bound to this protein as the body carries oxygen around to various organs. Transferrin saturation After the serum ferritin this is perhaps the next best index to look at when considering iron deficiency. This represents the proportion of iron that is bound to the transferrin protein. When the levels are less than 20% it may be an indicator of iron deficiency particularly functional iron deficiency.