Haemoglobin F

Babies are born with mostly HbF, which falls to adult levels by about a year; it is a little higher in pregnancy; use the range your lab printed.

Haemoglobin F is the type of haemoglobin made before birth, when it carries oxygen across the placenta. After birth it is gradually replaced by adult haemoglobin, and in most adults it makes up less than one per cent of the total. The test measures that percentage.

It is part of the haemoglobinopathy screen. Doctors look at it when looking into thalassaemia and sickle cell conditions, in antenatal screening, and in some bone marrow conditions. In sickle cell disease a higher HbF is helpful, and some medicines used for that condition are followed by measuring it.

• Inherited conditions where HbF persists into adult life, which cause no ill effects
• Beta thalassaemia and sickle cell conditions
• Pregnancy, slightly
• Hydroxycarbamide, a medicine used in sickle cell disease
• Some bone marrow conditions
• Recovery of the bone marrow after chemotherapy or transplant

• There is no common cause of a low HbF; values at or near zero are usual in adults

• A slightly raised value in pregnancy is expected
• Some people inherit a harmless tendency to keep making HbF
• Different laboratory methods give slightly different values
• A recent blood transfusion changes the proportion

No fasting needed. Interpreted together with the rest of the haemoglobin variant screen.

Written by a UK consultant physician. Typical UK adult reference ranges; your laboratory's own printed range takes precedence.