Lab result explainedHormonesLast updated November 10, 2026

AFP blood test: what alpha-fetoprotein means as a tumor marker and in pregnancy

Alpha-fetoprotein (AFP) · Tumor marker; maternal serum screen (quad screen: AFP, hCG, estriol, inhibin A) · reported in ng/mL (equivalent to µg/L); in pregnancy, multiples of the median (MoM)

Alpha-fetoprotein (AFP) is the main protein in the blood of a developing fetus, made by the fetal liver and yolk sac, and it falls to a trace within the first year or two after birth. In adults the normal level is under 10 ng/mL (some labs use 8 or 20). An AFP blood test is ordered for two quite different reasons. In people with liver disease or a testicular or ovarian mass it is a tumor marker, because liver cancer and certain germ cell tumors switch AFP production back on. In pregnancy, maternal serum AFP (MSAFP) at 15 to 22 weeks is a screening test for open neural tube defects and part of the quad screen.

As a tumor marker AFP is used to monitor rather than screen. In someone with cirrhosis or chronic hepatitis B, a level above 20 ng/mL raises suspicion of hepatocellular carcinoma and above 200 to 400 ng/mL in the presence of a liver mass is close to diagnostic, but a third of liver cancers never raise AFP and active hepatitis itself can push it to 100 or more. In testicular cancer, AFP identifies a non-seminoma, and the level before and after surgery helps assign risk and judge whether treatment has cleared the disease.

In pregnancy the result is reported as a multiple of the median (MoM) for the stage of pregnancy. A result above about 2.0 to 2.5 MoM is called screen-positive and leads to an ultrasound, not to a diagnosis: the most common explanation is that the pregnancy is further along than thought, followed by twins, with open spina bifida or anencephaly in a minority. A low MSAFP, read with hCG, estriol and inhibin A, increases the estimated risk of Down syndrome and is followed by a cell-free DNA test or diagnostic testing.

AFP at a glance

What it is: a fetal blood protein made by the liver and yolk sac; adult liver cells and some tumors (liver cancer, non-seminoma germ cell tumors) can produce it again.
Normal adult: under 10 ng/mL (labs use 8, 10 or 20). Units are ng/mL, the same as µg/L. Newborns are in the tens of thousands and reach adult levels within the first year or two.
Liver cancer: in cirrhosis or hepatitis B, AFP over 20 ng/mL prompts imaging; over 400 ng/mL with a liver mass is close to diagnostic. About a third of liver cancers have a normal AFP.
Testicular cancer: any raised AFP means a non-seminoma; levels under 1,000, 1,000 to 10,000 and over 10,000 ng/mL define good, intermediate and poor risk groups.
Pregnancy (MSAFP at 15–22 weeks): above 2.0–2.5 MoM is screen-positive for neural tube defects; below about 0.5–0.7 MoM contributes to Down syndrome risk. Wrong dates and twins are the commonest reasons for an abnormal result.
Next step: for a raised adult AFP, a liver ultrasound or contrast CT/MRI and hepatitis testing, or a testicular ultrasound; for an abnormal pregnancy screen, a dating and anatomy ultrasound and genetic counselling.

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What AFP measures

AFP is a glycoprotein closely related to albumin. Before birth it is the fetus's main carrier protein and is present in fetal blood at a few million ng/mL; it crosses into amniotic fluid through fetal urine and into the mother's blood across the placenta in tiny amounts. After birth the gene is switched off in liver cells, so a healthy adult has only trace levels. Hepatocellular carcinoma, hepatoblastoma and the yolk sac and embryonal components of germ cell tumors reactivate the gene, and regenerating liver cells in hepatitis do so to a lesser degree.

The lab measures AFP with an immunoassay in ng/mL. For tumor-marker use the raw number is reported against an adult reference limit. For pregnancy screening the same number is converted into a multiple of the median (MoM) for the exact gestational week, then adjusted for maternal weight, diabetes, race and whether it is a twin pregnancy, because the normal level roughly doubles between 15 and 20 weeks and an error of two weeks in dating is enough to turn a normal result into a positive one.

A refinement called AFP-L3 measures the fraction of AFP with a particular sugar structure; a fraction above 10 percent favors liver cancer over benign liver disease. It is sometimes combined with another marker, des-gamma-carboxy prothrombin (DCP), in people with cirrhosis. In germ cell tumors AFP is read with hCG and LDH, and its half-life of 5 to 7 days means the rate of fall after surgery is as informative as the level itself.

Normal range for AFP

Reference ranges vary between labs and by age, sex and pregnancy. Use the range printed on your own report.

Group	Typical range (ng/mL (equivalent to µg/L); in pregnancy, multiples of the median (MoM))	Notes
Adults, normal	Below 10 ng/mL	Labs use 8, 10 or 20 ng/mL as the upper limit; most healthy adults are under 5. Not affected by food or time of day.
Newborns and infants	Tens of thousands of ng/mL at birth, falling to adult levels by about 1 to 2 years	Age-specific reference ranges are used; a raised AFP in an infant is read against these.
Chronic hepatitis and cirrhosis without cancer	Usually below 20, occasionally 20–200 ng/mL during flares	Rises with liver inflammation and regeneration and falls as the hepatitis settles or is treated.
Hepatocellular carcinoma surveillance threshold	Above 20 ng/mL	Prompts contrast CT or MRI in people with cirrhosis or chronic hepatitis B. Sensitivity about 60 percent, so a normal AFP does not exclude cancer.
Strongly suggestive of hepatocellular carcinoma	Above 200–400 ng/mL with a liver mass in cirrhosis	Specificity over 95 percent at this level; values in the thousands or higher occur with large tumors.
Testicular germ cell tumor risk groups (IGCCCG)	Good: below 1,000; intermediate: 1,000–10,000; poor: above 10,000 ng/mL	Measured after orchiectomy together with hCG and LDH. Any raised AFP excludes pure seminoma.
Pregnancy screen, normal	About 0.5–2.0 MoM at 15–22 weeks	Reported as a multiple of the median for gestational age; the raw ng/mL rises from roughly 30 to 100 across this window.
Pregnancy screen, high	Above 2.0–2.5 MoM	Screen-positive for open neural tube and abdominal wall defects. Wrong dates and twins are the commonest explanations; about 1 in 20 to 1 in 50 screens is positive and most have a healthy baby.
Pregnancy screen, low	Below about 0.5–0.7 MoM	Read with hCG, estriol and inhibin A; contributes to an increased estimated risk of trisomy 21 or 18, or reflects overestimated dates.

High AFP

Outside pregnancy, a high AFP means the liver or a tumor is producing a fetal protein again, and the two questions are how high and in whom. In someone with cirrhosis or chronic hepatitis B or C, values between 10 and 20 ng/mL are common and often reflect liver inflammation; a result above 20 is the surveillance trigger for a contrast CT or MRI; and a value above 400 in a person with a liver mass is treated as hepatocellular carcinoma unless the imaging says otherwise. A rising AFP on serial testing, even within the normal range, carries more weight than a stable mildly raised one.

In a man with a testicular lump, or a woman or child with an ovarian or abdominal mass, a raised AFP points to a germ cell tumor with yolk sac or embryonal elements. Pure seminomas never make AFP, so an elevated level reclassifies the tumor as a non-seminoma and changes treatment. The level at diagnosis, and whether it falls at the expected rate (halving every 5 to 7 days) after the testicle is removed, feed into the risk group and into decisions about chemotherapy.

In pregnancy a high MSAFP means more fetal AFP than expected is reaching the mother's blood. Most often that is because the pregnancy is further along than the dates suggest or there is more than one fetus. Open defects of the fetal spine, skull or abdominal wall let AFP leak directly into the amniotic fluid and are the finding the screen is designed to catch; it identifies around 80 percent of open spina bifida and 90 percent of anencephaly at a 2.5 MoM cut-off. An unexplained high MSAFP with a normal ultrasound is also associated with later placental problems, so closer monitoring of growth and blood pressure is often advised.

Common causes

Hepatocellular carcinoma (liver cancer)
The classic cause; AFP is raised in about 60 to 70 percent of cases, often into the hundreds or thousands, and correlates with tumor size. Risk is highest with cirrhosis from any cause and chronic hepatitis B.
Chronic hepatitis B and C, and cirrhosis
Regenerating liver cells make AFP; levels of 10 to 100 ng/mL are common during active inflammation and fall with antiviral treatment. Persistently high or rising values still need imaging.
Non-seminomatous germ cell tumors
Yolk sac tumor, embryonal carcinoma and mixed tumors of the testis or ovary secrete AFP in 50 to 70 percent of cases; pure seminoma and pure choriocarcinoma do not.
Hepatoblastoma and other childhood tumors
The main liver cancer of young children produces very high AFP; it is also raised in some childhood germ cell tumors and must be read against age-specific infant ranges.
Other cancers
Stomach cancer of the hepatoid type, pancreatic, biliary, lung and colorectal cancers occasionally secrete AFP, usually at advanced stages; liver metastases rarely do.
Acute liver injury and recovery
Acute viral hepatitis, drug-induced liver injury and recovery after partial liver resection raise AFP transiently as the liver regrows, typically to 20 to 200 ng/mL.
Pregnancy: incorrect dating and multiple pregnancy
Because normal MSAFP roughly doubles between 15 and 20 weeks, dates that are 1 to 2 weeks too early produce a false positive; twins roughly double the level. A dating ultrasound resolves both.
Pregnancy: open neural tube defects
Anencephaly and open spina bifida let fetal AFP leak into the amniotic fluid and maternal blood, producing MSAFP above 2.5 MoM in 80 to 90 percent of cases. Closed defects do not raise it.
Pregnancy: abdominal wall defects and other fetal causes
Gastroschisis and omphalocele, congenital nephrosis, some skin disorders and fetal death all raise MSAFP; bleeding from fetus to mother and placental abnormalities do too.
Inherited conditions
Ataxia-telangiectasia produces a persistently raised AFP from childhood (useful diagnostically), and rare families have hereditary persistence of AFP with no disease at all.

Symptoms that can go with it

Often none; a raised AFP is usually found on surveillance in liver disease or on a routine pregnancy screen
Pain or fullness under the right ribs, unexplained weight loss, loss of appetite or a swollen abdomen (liver cancer)
Jaundice, dark urine, pale stools, itching or easy bruising with worsening liver disease
A painless lump, swelling or heaviness in a testicle, or back pain from enlarged lymph nodes
Pelvic pain or a mass in a young woman (ovarian germ cell tumor)
In pregnancy, no symptoms; a high screen result is followed by ultrasound, and twins or a dating error are often the finding
Fever, fatigue and nausea with a hepatitis flare

Low AFP

Outside pregnancy a low AFP has no significance. Healthy adults have very little and a value reported as below the detection limit is normal. In someone being followed for liver cancer or a germ cell tumor, a level that has fallen into the normal range and stays there is reassuring, though for liver cancer a normal AFP never excludes a tumor because a third of them do not produce it, and surveillance continues with ultrasound.

In pregnancy a low MSAFP, usually below about 0.5 to 0.7 MoM, is one of four markers in the quad screen that shift the estimated risk of chromosomal conditions. Down syndrome pregnancies have MSAFP around 0.7 MoM on average, with high hCG and inhibin A and low estriol; trisomy 18 has low values of AFP, hCG and estriol together. A low result on its own is weak evidence: the quad screen detects about 80 percent of Down syndrome pregnancies with a 5 percent false-positive rate, and most women with a positive screen have a baby without the condition. Cell-free DNA testing, which is far more accurate for Down syndrome, or diagnostic amniocentesis is the next step.

Common causes

Normal adult physiology
The AFP gene is switched off after infancy, so low or undetectable AFP is the expected adult result.
Successful treatment of an AFP-producing tumor
After complete removal, AFP halves every 5 to 7 days and should normalize within weeks; a slower fall suggests residual disease.
Pregnancy: trisomy 21 (Down syndrome)
Average MSAFP about 0.7 MoM, combined with raised hCG and inhibin A and low unconjugated estriol; the pattern, not the AFP alone, gives the risk estimate.
Pregnancy: trisomy 18
Low AFP, low hCG and low estriol together; usually accompanied by ultrasound findings.
Pregnancy: overestimated gestational age
If the pregnancy is earlier than the dates suggest, the expected median is too high and the MoM reads low; a dating ultrasound corrects it.
Pregnancy: maternal weight and diabetes
Heavier women and women with pre-existing diabetes have lower MSAFP; labs adjust the MoM for both, but an unadjusted result can appear low.

Symptoms that can go with it

None outside pregnancy; a low AFP does not cause symptoms
In pregnancy, no symptoms; the result is a risk estimate that is followed by cell-free DNA testing, detailed ultrasound or amniocentesis

Read it alongside

hCG and LDH — the other two germ cell tumor markers; together with AFP they define the risk group and are tracked after surgery.
ALT, AST and bilirubin — show whether active hepatitis explains a modest AFP rise; a liver cancer can raise AFP with little change in liver enzymes.
Platelets, albumin and PT/INR — markers of cirrhosis severity, which is the main risk setting for liver cancer and determines how it can be treated.
Hepatitis B surface antigen and hepatitis C antibody — the viral causes of chronic liver disease that make AFP surveillance worthwhile.
AFP-L3 fraction and DCP (des-gamma-carboxy prothrombin) — refine the probability of liver cancer when AFP is mildly raised in cirrhosis.
CEA and CA-125 — other tumor markers with the same rule: good for monitoring a known cancer, poor for screening the general population.
In pregnancy: hCG, unconjugated estriol and inhibin A — the other quad screen markers; the pattern across all four gives the aneuploidy risk.

What usually happens next

A raised adult AFP is repeated and, if confirmed or above 20 ng/mL in someone with liver disease, followed by a contrast CT or MRI of the liver; an ultrasound alone is not enough to characterise a mass in cirrhosis.
If you have cirrhosis or chronic hepatitis B, surveillance is an ultrasound (with or without AFP) every 6 months; ask that both be done, since adding AFP raises detection of early liver cancer from about 45 to over 60 percent.
A raised AFP in a man of any age should prompt a testicular examination and ultrasound even if nothing has been felt; hCG and LDH are checked at the same time.
For a screen-positive MSAFP in pregnancy, the first step is a detailed ultrasound to confirm dates, count fetuses and examine the spine, skull and abdominal wall; this resolves most high results and detects nearly all open defects. Amniocentesis for amniotic fluid AFP is reserved for unclear cases.
For a low MSAFP or a screen-positive quad result for Down syndrome, ask about cell-free DNA testing (over 99 percent detection for trisomy 21) before considering amniocentesis, and ask for genetic counselling.
Unexplained high MSAFP with a normal ultrasound is associated with preterm birth, growth restriction and preeclampsia; ask whether extra growth scans and blood pressure checks are planned.

Diet, lifestyle and natural levers with evidence

What can move AFP once the cause is known. Nothing here replaces finding the cause.

Folic acid before and during early pregnancy

Strong evidence

Folic acid prevents the condition a high MSAFP is screening for. In the MRC Vitamin Study, 4 mg of folic acid a day before conception reduced recurrence of neural tube defects by 72 percent in women who had a previously affected pregnancy, and population fortification has cut rates by about a quarter to a third. The US Preventive Services Task Force recommends 400 to 800 micrograms a day for anyone who could become pregnant, started at least a month before conception, because the neural tube closes by 4 weeks, before most pregnancies are recognized.

Women with a previous affected pregnancy, on certain anti-seizure medicines, or with diabetes are usually advised a higher dose by their clinician; do not self-prescribe 4 mg.

Not drinking alcohol when you have liver disease

Strong evidence

Alcohol does not change AFP directly, but it drives the cirrhosis in which liver cancer arises. Continued drinking in chronic hepatitis C roughly doubles the risk of hepatocellular carcinoma, and in alcohol-related cirrhosis abstinence is the main thing that stabilizes liver function, reduces AFP fluctuation from ongoing injury, and keeps someone eligible for treatment or transplant if a cancer is found.

Coffee

Moderate evidence

A meta-analysis of 18 cohort and case-control studies covering over 2 million people found that each additional 2 cups of coffee a day was associated with a 35 percent lower risk of hepatocellular carcinoma, with a similar pattern for decaffeinated coffee and in people with existing liver disease. The evidence is observational and cannot prove cause, but it is consistent across populations and coffee is also linked to slower fibrosis progression.

Weight loss in fatty liver disease

Moderate evidence

Fatty liver disease is now a leading cause of cirrhosis and liver cancer. In a 52-week study of 293 people with biopsy-proven steatohepatitis, losing 7 to 10 percent of body weight resolved the inflammation in most and losing 10 percent or more produced fibrosis regression in nearly half. Reducing fibrosis reduces the setting in which AFP surveillance becomes necessary.

Get the dates right before a pregnancy screen

Strong evidence

The single biggest influence on a pregnancy AFP result is gestational age. Because the median MSAFP roughly doubles between 15 and 20 weeks, dates that are 1 to 2 weeks out convert a normal result into a screen-positive one, and incorrect dating and twins are the most common explanations for a high MSAFP. A first-trimester ultrasound to confirm dates before the 15 to 22 week screen, and drawing the sample at 16 to 18 weeks, minimize false positives. Nothing dietary or herbal changes the result.

When to see a clinician promptly

An AFP above 20 ng/mL if you have cirrhosis or chronic hepatitis B or C, or any AFP that is rising on repeat tests, for liver imaging within weeks rather than months.
A raised AFP with a testicular lump or swelling, or in any man of any age, for urgent testicular ultrasound; germ cell tumors are highly treatable and delay matters.
Jaundice, a swollen abdomen, confusion or drowsiness, or vomiting blood or passing black stools in someone with liver disease: these are emergencies.
Severe pain or sudden swelling of a testicle, which can be torsion and needs emergency care regardless of any blood test.
In pregnancy, a screen-positive MSAFP result: ask for the follow-up ultrasound within 1 to 2 weeks and for genetic counselling, since decisions about further testing are time-sensitive.
Reduced fetal movements, bleeding, severe headache or visual disturbance later in a pregnancy with an unexplained high MSAFP, which carries a higher risk of placental problems.

Frequently asked questions

What is a normal AFP level?

In adults who are not pregnant, under 10 ng/mL is normal on most assays, though some labs use 8 or 20, and most healthy people are under 5. ng/mL and µg/L are the same number. Newborns have levels in the tens of thousands that fall to adult values over the first year or two. In pregnancy the result is given as a multiple of the median (MoM) for the gestational week, with roughly 0.5 to 2.0 MoM considered normal.

What AFP level indicates liver cancer?

There is no single number. In someone with cirrhosis or chronic hepatitis B, an AFP above 20 ng/mL is the trigger for a contrast CT or MRI, above 200 ng/mL makes cancer likely, and above 400 ng/mL with a liver mass is close to diagnostic. However, about a third of liver cancers never raise AFP, and hepatitis flares can push it to 100 or more without cancer, so imaging, not the AFP, makes the diagnosis.

Can AFP be high without cancer?

Yes. Chronic hepatitis B and C, cirrhosis, acute hepatitis, drug-induced liver injury and liver regeneration after surgery all raise it, usually to 10 to 100 ng/mL and occasionally higher during flares. Pregnancy raises it as a matter of course. Ataxia-telangiectasia and a rare inherited trait cause a lifelong raised AFP. A mildly raised value that stays stable is usually benign; one that is rising needs imaging.

What does a high AFP in pregnancy mean?

An MSAFP above about 2.0 to 2.5 MoM at 15 to 22 weeks is called screen-positive. The most common reasons are that the pregnancy is further along than the dates suggest or that there are twins. In a minority, the baby has an open neural tube defect (spina bifida or anencephaly) or an abdominal wall defect, which an ultrasound can usually see. Roughly 1 in 20 to 1 in 50 screens is positive and the large majority of those pregnancies are healthy.

What does a low AFP in pregnancy mean?

A low MSAFP, read together with hCG, estriol and inhibin A, raises the estimated risk of Down syndrome (trisomy 21) or trisomy 18, or simply reflects dates that are later than the pregnancy really is. The quad screen is a risk estimate, not a diagnosis: it flags about 80 percent of Down syndrome pregnancies with a 5 percent false-positive rate. Cell-free DNA testing or amniocentesis gives a definitive answer.

When is the AFP pregnancy test done?

Between 15 and 22 weeks, ideally at 16 to 18 weeks when the test performs best. Accurate dating matters because the normal level roughly doubles across this window; a first-trimester ultrasound to confirm dates reduces false positives. Women who have had cell-free DNA screening for chromosomal conditions are still offered MSAFP or a detailed ultrasound for neural tube defects, which cell-free DNA does not detect.

Is AFP raised in seminoma?

No. Pure seminoma never produces AFP, so any raised AFP in a man with a testicular tumor means there is a non-seminomatous component (yolk sac or embryonal carcinoma) even if the pathology report says seminoma, and the cancer is treated as a non-seminoma. hCG can be mildly raised in seminoma. After the testicle is removed, AFP should halve every 5 to 7 days; a slower fall suggests disease remains.

How often should AFP be checked in cirrhosis?

Guidelines recommend liver cancer surveillance every 6 months in people with cirrhosis and in many with chronic hepatitis B, using ultrasound with or without AFP. Adding AFP to ultrasound increases detection of early-stage cancer from about 45 percent to over 60 percent in pooled studies. A value above 20 ng/mL, or one that is climbing, leads to contrast CT or MRI even if the ultrasound looks normal.

References

Alpha-fetoprotein (AFP) tumor marker test. MedlinePlus, US National Library of Medicine (2023)View source
Singal AG, Llovet JM, Yarchoan M, et al.. AASLD practice guidance on prevention, diagnosis, and treatment of hepatocellular carcinoma. Hepatology (2023)
Tzartzeva K, Obi J, Rich NE, et al.. Surveillance imaging and alpha fetoprotein for early detection of hepatocellular carcinoma in patients with cirrhosis: a meta-analysis. Gastroenterology (2018)
Gilligan TD, Seidenfeld J, Basch EM, et al.. American Society of Clinical Oncology clinical practice guideline on uses of serum tumor markers in adult males with germ cell tumors. Journal of Clinical Oncology (2010)
International Germ Cell Cancer Collaborative Group. International Germ Cell Consensus Classification: a prognostic factor-based staging system for metastatic germ cell cancers. Journal of Clinical Oncology (1997)
American College of Obstetricians and Gynecologists. Practice Bulletin No. 187: Neural tube defects. Obstetrics & Gynecology (2017)
American College of Obstetricians and Gynecologists. Practice Bulletin No. 226: Screening for fetal chromosomal abnormalities. Obstetrics & Gynecology (2020)
Dugoff L, Hobbins JC, Malone FD, et al.. Quad screen as a predictor of adverse pregnancy outcome. Obstetrics & Gynecology (2005)
MRC Vitamin Study Research Group. Prevention of neural tube defects: results of the Medical Research Council Vitamin Study. The Lancet (1991)
US Preventive Services Task Force. Folic acid supplementation to prevent neural tube defects: US Preventive Services Task Force reaffirmation recommendation statement. JAMA (2023)
Kennedy OJ, Roderick P, Buchanan R, et al.. Coffee, including caffeinated and decaffeinated coffee, and the risk of hepatocellular carcinoma: a systematic review and dose-response meta-analysis. BMJ Open (2017)
Vilar-Gomez E, Martinez-Perez Y, Calzadilla-Bertot L, et al.. Weight loss through lifestyle modification significantly reduces features of nonalcoholic steatohepatitis. Gastroenterology (2015)

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This page is educational and is not medical advice or a diagnosis. Lab results have to be interpreted together with your history, symptoms and other results by a clinician who knows you. Do not start or stop a supplement to change a lab value before the cause is known.