AFP (Alpha-Fetoprotein)
A protein made by a baby's liver before birth. Adults who aren't pregnant normally have very little. Doctors follow it in some liver and germ cell conditions.
AI-verified against cited sources. Awaiting expert reviewAlso called AFPLOINC 53962-7
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What it is
AFP (alpha-fetoprotein) is a protein made mostly by a baby's liver before birth. Levels are very high in newborns and fall to a low level over the first year or two of life. Children and adults who aren't pregnant make only a little. Because of this, the test is mostly used as a tumor marker, which is a blood substance that doctors follow in people with certain conditions. AFP is also measured during pregnancy, but those results are read in a different way.
Why it matters
Doctors use AFP in two main ways. One is to follow people who have liver cancer or a germ cell tumor (a tumor that starts in a testicle or an ovary). The test helps show how treatment is working and whether the condition has come back. The other is to keep watch on people at higher risk of liver cancer, such as those with cirrhosis and some people with chronic hepatitis B, usually along with a liver ultrasound about every 6 months. AFP can't diagnose or rule out cancer on its own. Some tumors never raise it, and liver inflammation, cirrhosis and pregnancy can raise it with no cancer at all.
If it’s high
A result above your lab's range does not mean you have cancer. In adults who aren't pregnant, mild or moderate rises are often caused by liver inflammation or scarring. Higher values are more common in people with liver cancer or certain germ cell tumors, and very high values are less often explained by non-cancer causes. Your clinician will look at the number together with your history, an exam, imaging and other blood tests, and may repeat the test.
Common causes
- Pregnancy (the baby makes AFP, so pregnancy results are read differently)
- Liver inflammation, such as acute or long-term hepatitis B or C, or alcohol-related liver disease
- Cirrhosis (scarring of the liver) and liver cells regrowing after an injury
- Being a hepatitis B carrier
- In newborns and young infants, high levels are normal and fall over the first year
- A rare inherited trait that keeps AFP high for life (hereditary persistence of AFP)
- Liver cancer (hepatocellular carcinoma)
- Germ cell tumors of the testicle or ovary
- Less often, other cancers such as some stomach, bile duct or other gut cancers
What can help
- Ask your clinician whether to repeat the test, since one result rarely settles the question
- Tell your clinician about liver disease, hepatitis, pregnancy, recent liver injury, and any biotin supplements you take
- If you have cirrhosis or chronic hepatitis B, ask your clinician whether regular liver cancer surveillance (a liver ultrasound with AFP about every 6 months) applies to you
- Use the same lab for repeat tests when you can, since methods differ between labs
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 sex and age. Choose women or men to see the one that applies.
- 18+0–8.4 ng/mL
Source: Mayo Clinic Laboratories
- Men, 18–300–5.7 ng/mL
Source: Labcorp
- Women, 18–300–4.7 ng/mL
Source: Labcorp
- Men, 31–500–6.9 ng/mL
Source: Labcorp
- Women, 31–500–6.4 ng/mL
Source: Labcorp
- Men, 51–800–8.4 ng/mL
Source: Labcorp
- Women, 51–800–9.2 ng/mL
Source: Labcorp
- Men, 81+0–6.4 ng/mL
Source: Labcorp
- Women, 81+0–8.7 ng/mL
Source: Labcorp
See AFP by age and sex, with the U.S. survey numbers where they exist.
What can affect your result
- Pregnancy: AFP rises during pregnancy, so ranges for people who aren't pregnant don't apply
- Age: newborns have very high levels that fall over the first year, and adult limits vary a little with age
- Sex: Labcorp's adult limits differ slightly between men and women
- Liver conditions: hepatitis, cirrhosis and liver recovery after injury can raise AFP
- Assay method: results from different methods can't be compared directly
- Biotin supplements and rare antibodies can interfere with some methods
- High-dose biotin (vitamin B7, found in many hair, skin and nail supplements) can interfere with some immunoassays. Labcorp asks people to stop biotin at least 72 hours before the draw for its method. Ask your lab.
- Rare antibodies in the blood can cause false results on some methods. Examples are antibodies to mouse proteins (from some treatments or scans) and to streptavidin or ruthenium.
- Asfotase alfa (Strensiq) may falsely raise results on some assays, according to Quest.
- Pregnancy raises AFP, so ranges for people who are not pregnant do not apply.
- Very high levels can read falsely low on some immunoassays (the high-dose hook effect). Mayo says its Beckman Access method is not expected to do this below 500,000 ng/mL.
- Results from different methods can't be compared directly, so use the same lab for follow-up testing when you can.
- Labcorp rejects citrate plasma and Mayo rejects grossly hemolyzed samples.
AFP has a half-life of about 5 days (Mayo), so it falls over several weeks after successful treatment. Mayo says an AFP that has not returned to normal about one month after surgery suggests some tumor remains.
When to talk to a clinician
Talk with the clinician who ordered the test if your result is above your lab's range, especially if it keeps rising on repeat tests. If you are in liver cancer surveillance, for example because of cirrhosis, let your care team know soon about an AFP above 20 ng/mL or one that is climbing. Guidelines use 20 ng/mL as the level that most often prompts further imaging in liver cancer surveillance. Get care promptly for yellowing of your skin or eyes, belly pain or swelling, or a lump or swelling in a testicle.
Questions you could ask
- Why was AFP ordered for me, and how will we use the result?
- Should I use the same lab each time I'm tested?
- Do any supplements I take, such as biotin, affect this test?
- Should we repeat this test, and when?
- Could a liver condition, pregnancy or something else explain this result?
- Would a liver ultrasound or other tests help put this number in context?
Questions people ask
Does a high AFP mean I have cancer?
No. AFP can be raised by liver inflammation, cirrhosis, hepatitis B or C, and pregnancy. Higher values are more common in people with liver cancer or certain germ cell tumors, but some people with those cancers have a normal AFP. Your clinician will use your history, an exam and imaging to put the number in context.
Why do labs print different AFP ranges?
Labs use different methods and study their own groups of healthy people. Labcorp's adult limits run from about 4.7 to 9.2 ng/mL depending on age and sex, and Mayo Clinic Laboratories uses under 8.4 ng/mL for all adults who aren't pregnant. Use the range printed on your own report and ask your clinician how it applies to you.
I'm pregnant. Does my AFP result mean the same thing?
No. AFP rises in pregnancy because the baby makes it, and what's expected changes week by week. Prenatal reports usually give a multiple of the median (MoM) for your stage of pregnancy instead. Talk with your prenatal provider about what your result means.
Show the science and sources
Units
- 1 ng/mL = 1 ng/mL
- 1 ng/mL = 1 µg/L
- 1 ng/mL = 0.8264 IU/mL
- 1 ng/mL = 0.8264 kIU/L
Is a change real?
AFP naturally varies about 4.6% from test to test in the same healthy person. Between two results from the same lab, a rise of 15% or more, or a fall of 13% or more, is unlikely to be day-to-day noise or lab variation (95% reference change value). Source: Critical review and meta-analysis of biological variation estimates for tumor markers (Marques-Garcia F et al., EFLM WG-BV).
For clinicians and researchers
AFP is an oncofetal glycoprotein of about 70 kDa made by the fetal yolk sac, liver and gut. Its half-life is about 5 days (Mayo). In adults it is re-expressed by hepatocellular carcinoma (HCC), hepatoblastoma and non-seminomatous germ cell tumors, and by regenerating liver. It is not raised in pure seminoma. Mayo reports elevated AFP in about 70% of HCC and 50% to 70% of non-seminomatous testicular tumors. The 2023 AASLD guidance notes that over 40% of HCC have a normal AFP, and AFP at a 400 ng/mL cutoff is no longer recommended for HCC diagnosis. For HCC surveillance in high-risk groups (cirrhosis, and some people with chronic hepatitis B), AASLD recommends ultrasound plus AFP about every 6 months. A 20 ng/mL cutoff gives a sensitivity of about 60% and a specificity of about 90% and is the most common threshold, although the best cutoff may be lower in non-viral cirrhosis. The NACB 2008 guideline recommends AFP, hCG and LDH in testicular cancer for diagnosis, staging, prognosis, recurrence detection and therapy monitoring, and AFP for telling non-seminomatous from seminomatous tumors. After treatment, failure of AFP to normalize about one month after surgery suggests residual tumor, and a rise after remission suggests recurrence, although a tumor that once made AFP can recur without it (Mayo). Reference limits are method-specific. Labcorp (Roche Elecsys ECLIA, in-house study) publishes limits by age and sex: 4.7 to 9.2 ng/mL in adults, up to 75,265.8 ng/mL in the first week of life, 21.4 ng/mL at age 1 year, and 60.3 ng/mL at 7 to 11 months. Mayo (Beckman Access) uses under 8.4 ng/mL for people who are not pregnant. Labcorp and Mayo both warn that values from different methods can't be used interchangeably in serial testing. In pregnancy, maternal serum AFP is interpreted as a multiple of the median (MoM) for gestational age. Mayo's single-marker maternal screen reports an MoM of 2.5 or higher as screen positive for singleton and twin pregnancies. Immunoassay caveats: biotin (Labcorp advises stopping at least 72 hours before collection), heterophile and anti-mouse antibodies, anti-streptavidin and anti-ruthenium antibodies (Labcorp), asfotase alfa (Quest), and the high-dose hook effect. Some labs report AFP in IU/mL or kIU/L (which are numerically equal). This catalog converts at 1 IU/mL = 1.21 ng/mL, which matches the Roche Elecsys AFP measuring range (0.50 to 1,000 IU/mL, or 0.605 to 1,210 ng/mL) and Lao 2016. The true factor can depend on the assay's calibration, so check the unit and range printed on your report.
LOINC 53962-7 (primary), 1834-1, 83073-7. Specimen: serum.
Sources
- AFP, Serum, Tumor Marker (test 002253), Labcorp
- AFP - Overview: Alpha-Fetoprotein (AFP) Tumor Marker, Serum, Mayo Clinic Laboratories
- Alpha-Fetoprotein, Tumor Marker (test code 237), Quest Diagnostics
- AFP Single Marker Screen, Maternal, Serum (MAFP1), Mayo Clinic Laboratories (Extended Catalog)
- Alpha Fetoprotein (AFP) Tumor Marker Test, MedlinePlus (National Library of Medicine) (2026)
- Alpha-Fetoprotein (AFP) Test, MedlinePlus (National Library of Medicine) (2024)
- AASLD Practice Guidance on prevention, diagnosis, and treatment of hepatocellular carcinoma, Hepatology (2023)
- Reference Intervals for Alpha-Fetoprotein (AFP) and Carcinoembryonic Antigen (CEA) in Guangxi Zhuang Ethnic Males from the FAMHES Project, Clinical Laboratory (2016)
- National Academy of Clinical Biochemistry laboratory medicine practice guidelines for use of tumor markers in testicular, prostate, colorectal, breast, and ovarian cancers, Clinical Chemistry (2008)
- Tumor Marker Tests in Common Use, National Cancer Institute (2023)
- Elecsys AFP factsheet, Roche Diagnostics
AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.