Hemoglobin F (HbF / Foetal Hemoglobin)
Hemoglobin F is the dominant hemoglobin during fetal life and the first six months after birth, after which it is replaced by adult HbA. HbF binds oxygen more tightly than HbA, which helps a fetus extract oxygen from the mother's blood. In adults, HbF should be less than 2%. Persistent high levels in adults can indicate inherited disorders, bone marrow stress, or response to certain treatments.
Reference Ranges
Male
0 – 2
%
Female
0 – 2
%
Child
0 – 8
%
Higher in infants; <2% by age 2
Reference ranges may vary by laboratory. Always compare with the range printed on your lab report.
What Low Levels Mean
HbF below 2% is the normal adult range and expected. A very low HbF has no clinical significance on its own.
What High Levels Mean
HbF above 2% in adults can indicate beta-thalassemia major (often 50–90%) or intermedia, delta-beta thalassemia, hereditary persistence of fetal hemoglobin (HPFH), sickle cell disease (a high HbF protects against severe crises), aplastic anemia, or response to hydroxyurea therapy. In newborns, failure of HbF to decline by age 2 suggests a hemoglobinopathy.
Frequently Asked Questions
Why is HbF helpful in sickle cell disease?
HbF does not sickle and interferes with the polymerization of HbS that causes red cells to deform. Sickle cell patients with naturally higher HbF have fewer pain crises and better outcomes. Hydroxyurea, a standard sickle cell treatment, works partly by raising HbF levels. Newer drugs like voxelotor and crizanlizumab add further options.
What is hereditary persistence of fetal hemoglobin (HPFH)?
A benign inherited condition where HbF continues to be produced at 10–30% into adulthood. HPFH carriers are clinically normal. Its main importance is that when combined with sickle cell or beta-thalassemia genes, it softens those diseases significantly. HPFH is identified on hemoglobin electrophoresis.
Should HbF be measured during pregnancy?
Not routinely. Maternal HbF rises slightly during normal pregnancy. HbF is tested during pregnancy mainly when fetomaternal hemorrhage is suspected after trauma or bleeding — quantifying fetal red cells in maternal blood guides anti-D immunoglobulin dosing in Rh-negative mothers.
Related Blood Count tests
See all →Hemoglobin (Hb)
Oxygen-carrying protein in red blood cells.
g/dLBlood CountHematocrit (HCT)
Percentage of blood volume occupied by red blood cells.
%Blood CountRed Blood Cell Count (RBC)
Total number of red blood cells per unit of blood.
million/µLBlood CountWhite Blood Cell Count (WBC)
Total number of immune cells fighting infection in your blood.
thousand/µLThis information is for educational purposes only and should not replace professional medical advice. Always consult your doctor for interpretation of your test results.
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