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Hemoglobin F (Fetal Hemoglobin)

The share of your hemoglobin that is the fetal type, HbF. It is high in newborns and falls to a very low level after the first two years.

AI-verified against cited sources. Awaiting expert reviewAlso called HbF, Hb F, HGB FLOINC 4576-5

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What it is

Before birth, a baby makes mostly fetal hemoglobin (HbF). After birth, the body switches to adult hemoglobin (HbA), and HbF falls over the first one to two years of life. In most adults HbF is a tiny share of the total. This test reports the percent of HbF using HPLC or capillary electrophoresis, usually as part of a hemoglobin evaluation. It is not the same as the Kleihauer-Betke test or F-cell counts, which look for fetal cells in a different way.

Why it matters

A higher-than-usual HbF in an older child or adult can be a sign of an inherited hemoglobin condition. In beta-thalassemia and sickle cell disease, extra HbF is helpful, because it can soften the condition. Some people inherit a persistently higher HbF with no health problems. HbF also matters for other tests, because a high level can affect the accuracy of some HbA1c methods.

If it’s high

In a child over two or an adult, a result above your lab's range means more fetal hemoglobin than usual is being made. It can be an inherited trait that causes no problems, or it can go along with a hemoglobin condition such as beta-thalassemia or sickle cell disease. Your clinician reads it together with your other hemoglobin results and red cell indices.

Common causes

  • An inherited trait that keeps HbF high without symptoms (hereditary persistence of fetal hemoglobin, or HPFH)
  • Beta-thalassemia, including carriers, where HbF may be mildly raised (about 0.1% to 5% in trait)
  • Sickle cell disease, where HbF is often raised and can be raised further by some treatments
  • Other conditions that speed up red cell production

What can help

  • Ask your clinician to read the result with the rest of your hemoglobin report and your CBC
  • Ask whether an HbF level could affect how your HbA1c is measured

Usual ranges

What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.

The usual range depends on age. Choose an age to see the one that applies.

Children and teens 8 ranges

See HbF by age and sex, with the U.S. survey numbers where they exist.

What can affect your result

  • Age: HbF is high at birth and falls over the first two years
  • Hemoglobin conditions such as beta-thalassemia and sickle cell disease
  • Treatments such as hydroxyurea that raise HbF, and transfusions that lower the share
  • The lab method: HPLC and capillary electrophoresis give different ranges
  • Inherited differences: HbF varies more than tenfold between healthy adults
  • A recent blood transfusion adds donor red cells, which lowers the HbF share. Mayo lists this test for tracking HbF and variants after transfusion or treatment.
  • Treatment that raises HbF in sickle cell disease (such as hydroxyurea) changes the result.
  • Babies have much higher HbF than adults, so adult ranges do not fit them.
  • HPLC and capillary electrophoresis give different ranges, for example 0.0–2.1% and 0.0–0.9% for adults.
  • HbF can affect HbA1c results on some methods (National Glycohemoglobin Standardization Program).

In a healthy adult HbF is steady. After a treatment that raises it, the change builds up over weeks to months as new red cells are made.

When to talk to a clinician

In babies and toddlers a high HbF is expected. In an older child or adult, a result above your lab's range is not urgent by itself, but talk with the clinician who ordered it, especially if you are pregnant or planning a pregnancy or have a family history of thalassemia or sickle cell disease. Call 911 or your local emergency number for chest pain, fainting or severe trouble breathing.

Questions you could ask

  • Do I need this test repeated, or is one result enough?
  • Does my HbF fit with a hemoglobin condition, or could it be an inherited trait with no effect?
  • Could my HbF affect how my HbA1c is measured?

Questions people ask

Why is a baby's fetal hemoglobin so high?

Fetal hemoglobin carries oxygen well before birth. After birth the body switches to adult hemoglobin, and HbF falls over the first one to two years. ARUP's range for the first two months is about 33% to 92%, and by age two it is 0.0–2.1%.

Is a high HbF in an adult a problem?

Not by itself. Some people inherit a persistently higher HbF with no health problems, and in sickle cell disease and beta-thalassemia a higher HbF is helpful. A raised value is still worth reviewing with your clinician, together with your red cell indices and the full hemoglobin report.

Is this the same as the test for fetal blood in a mother's blood?

No. The Kleihauer-Betke test and F-cell counts look for fetal cells in a different way. This test reports the percent of hemoglobin that is HbF in your own blood.

Show the science and sources

For clinicians and researchers

HbF (alpha2-gamma2) is quantified by cation-exchange HPLC or capillary electrophoresis. Adult synthesis is normally reduced to below 0.6% of total hemoglobin, concentrated in a subset of red cells called F-cells; 85% of healthy adults have 0.3% to 4.4% F-cells, and HbF varies more than tenfold between normal adults under genetic control (Rochette 1994). Intervals: ARUP (HPLC) 0.0–2.1% from age 2 with the age table 45.8–91.7% at 0 to 1 months to 0.0–8.5% at 13 to 23 months; Mayo (capillary electrophoresis) 0.0–0.9% from 24 months, with 22.8–92.0% in the first 30 days; University of Iowa 2% or less after 1 year. HbF rises in adults in many inherited and acquired disorders, often with a higher erythropoietic drive, and raised HbF lessens sickle cell disease and beta-thalassemia severity (Wood 1993). AAFP lists HbF at 0.1% to 5% in beta-thalassemia trait and 10% to 50% (up to 100%) in beta-thalassemia major. The NHS England antenatal programme uses HbF action values of 10% or more when MCH is 27 pg or higher and 5.0% or more when MCH is under 27 pg. Mayo reflexes HbF distribution by flow cytometry to help identify HPFH. Genetic variants and elevated HbF can interfere with HbA1c methods (NGSP). No critical value was found.

LOINC 4576-5 (primary), 32682-7, 42246-9. Specimen: whole-blood.

Sources

  1. Hemoglobin Evaluation by HPLC With Reflex to Electrophoresis and/or RBC Solubility (test 3017101), ARUP Laboratories
  2. Hemoglobin Variant, A2 and F Quantitation, Blood (test HGBCE), Mayo Clinic Laboratories
  3. Hemoglobin Evaluation, Quantitation with Interpretation (Pathology Handbook), University of Iowa Hospitals & Clinics
  4. Alpha- and Beta-thalassemia: Rapid Evidence Review, American Family Physician (2022)
  5. Sickle cell and thalassaemia screening: laboratory handbook, Antenatal screening (updated 10 October 2024), NHS England (NHS Sickle Cell and Thalassaemia Screening Programme) (2024)
  6. Fetal hemoglobin levels in adults, Blood Reviews (1994)
  7. Increased HbF in adult life, Baillière's Clinical Haematology (1993)
  8. Factors that Interfere with HbA1c Test Results, National Glycohemoglobin Standardization Program (NGSP) (2026)

AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.

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