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Bile Acids, Total (fasting)

Bile acids are made by the liver to digest fat. Their level in a fasting blood sample can rise when bile isn't flowing out of the liver normally.

AI-verified against cited sources. Awaiting expert reviewAlso called TBA, TSBALOINC 14628-2

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What it is

Your liver makes bile acids from cholesterol and sends them into bile. After a meal, bile acids flow into the gut to help digest fat, and most are taken back up and sent to the liver again. Only a small amount stays in the blood, so a fasting level is normally low. The test measures the total of all bile acids in the blood.

Why it matters

A raised bile acid level can show that bile isn't draining well, sometimes before yellow skin or eyes appear. The test is most often used when a pregnant person has itching and clinicians want to check for intrahepatic cholestasis of pregnancy (ICP). In that situation the level also helps guide how closely the pregnancy is watched. It is also used to look into other liver and bile duct problems.

If it’s high

A level above your lab's range means bile acids are building up in the blood. A recent meal can cause this in a test that was meant to be fasting. Otherwise it is linked to slowed bile flow, called cholestasis.

Common causes

  • Eating before a test meant to be fasting
  • Cholestasis of pregnancy, which usually shows up in the late second or third trimester
  • Liver conditions that slow bile flow, such as hepatitis, cirrhosis, or primary biliary cholangitis
  • A blocked bile duct, for example by gallstones
  • Liver injury from medicines or other chemicals
  • Rare inherited conditions of bile flow

What can help

  • Ask whether a repeat fasting sample would clarify the result
  • Ask which other tests, such as ALT, AST, ALP, GGT, bilirubin or an ultrasound, would help
  • Review your medicines and supplements with your clinician

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.

For adults: 0–10 µmol/L. Source: Mayo Clinic Laboratories, ARUP Laboratories, The Lancet.

Cholestasis of pregnancy: stillbirth-risk groups from a meta-analysis of singleton pregnancies (the 100 µmol/L cut point is also used by SMFM)

  • Below 40below 40 µmol/L
  • 40 to 9940 to under 100 µmol/L
  • 100 or more100 and above µmol/L

Cholestasis of pregnancy: stillbirth-risk groups from a meta-analysis of singleton pregnancies (the 100 µmol/L cut point is also used by SMFM)

  • Below 40below 40 µmol/L
  • 40 to 9940 to under 100 µmol/L
  • 100 or more100 and above µmol/L

What can affect your result

  • Fasting: a meal raises bile acids, so a sample after eating can read higher
  • Pregnancy: labs use their own upper limits, from about 10 to 14 µmol/L
  • Treatment with ursodeoxycholic acid or cholic acid, which can change how the test should be done
  • Hemolysis and delays in separating the serum
  • Lab method: enzymatic assays and LC-MS/MS fractionated tests are different tests
  • A meal raises bile acids, so a sample taken after eating can read above the fasting range. Mayo requires a 12-hour fast and ARUP asks for 8 hours; Mayo says infants and pregnant patients do not need to fast.
  • In women with cholestasis of pregnancy, median bile acids were higher after a meal than when fasting (32 versus 23 µmol/L) in one large analysis (Ovadia 2019).
  • Mayo points patients treated with ursodeoxycholic acid or cholic acid to a different, fractionated test rather than total bile acids.
  • ARUP rejects hemolyzed samples. Mayo asks that the serum be separated within 2 hours.

In pregnancy-related cholestasis, levels typically settle quickly after delivery. For other liver and bile duct conditions, how fast the level changes depends on the cause.

When to talk to a clinician

If you're pregnant and have itching, especially on your hands and feet, contact your maternity team promptly, even if your bile acid result is not yet back. In ICP, the Society for Maternal-Fetal Medicine recommends offering delivery at 36 weeks when total bile acids are 100 µmol/L or more, and your obstetric team decides what is right for you. Contact your clinician soon if you have yellow skin or eyes, dark urine, pale stools or belly pain with a raised level.

Questions you could ask

  • Does my lab's range apply to a fasting or a non-fasting sample?
  • Was this a fasting sample, and should we repeat it?
  • Do my other liver tests, or an ultrasound, give any clues?
  • If I'm pregnant, how often should we recheck bile acids, and how will the result guide my care?
  • Could a medicine or supplement be involved?

Questions people ask

Why do I need to fast for a bile acid test?

Eating makes the gallbladder release bile and raises bile acids in the blood. The lab's range is for a fasting sample, so a sample after a meal can look high. Mayo says infants and pregnant patients do not need to fast, so follow your clinician's instructions.

I'm pregnant and my bile acids are slightly above my lab's range. Is that a problem?

Your lab's range, your symptoms and your other liver tests all matter, so your clinician is the best person to put it in context. Labs set different upper limits in pregnancy, from about 10 to 14 µmol/L in one trial. Bile acids are often repeated to see which way the level is heading.

Is a bile acid test the same as a bilirubin test?

No. Both can rise when bile isn't flowing well, but they measure different things. Mayo describes bile acids as a way to pick up changes in liver function before more advanced signs such as yellow skin or eyes appear.

Show the science and sources

Units

  • 1 µmol/L = 1 µmol/L
  • 1 µmol/L = 1 nmol/mL

For clinicians and researchers

Total bile acids are the sum of conjugated primary (cholic, chenodeoxycholic) and secondary (deoxycholic, lithocholic) acids, normally measured by enzymatic assay (Mayo and ARUP list enzymatic methods). Fractionated LC-MS/MS profiles are separate tests, and Mayo advises them for patients on ursodeoxycholic or cholic acid. Because the enterohepatic circulation is stimulated by feeding, fasting and postprandial results are separate concepts, and the Mayo and ARUP intervals apply to fasting samples. For ICP, an individual-patient-data meta-analysis found no clear increase in stillbirth with bile acids under 100 µmol/L, and a markedly higher risk at 100 µmol/L or more in singleton pregnancies, with no clear link in twin pregnancies (Ovadia 2019); SMFM Consult #53 recommends offering delivery at 36 0/7 weeks at that level (SMFM 2021). The analysis mixed fasting and non-fasting samples, with median levels of 23 µmol/L fasting and 32 µmol/L after eating among ICP cases. National guidelines differ on diagnostic thresholds and timing of delivery (Bicocca 2018), and upper limits of normal in pregnancy varied from 10 to 14 µmol/L across UK sites (PITCHES 2019). Total bile acids may be reported in nmol/mL, which is numerically identical to µmol/L.

LOINC 14628-2 (primary), 35562-8, 1967-9. Specimen: serum.

Sources

  1. Bile Acids, Total, Serum (test ID BILEA), Mayo Clinic Laboratories
  2. Bile Acids, Total (test 0070189), ARUP Laboratories
  3. Association of adverse perinatal outcomes of intrahepatic cholestasis of pregnancy with biochemical markers: results of aggregate and individual patient data meta-analyses, The Lancet (2019)
  4. Society for Maternal-Fetal Medicine Consult Series #53: Intrahepatic cholestasis of pregnancy: Replaces Consult #13, April 2011, American Journal of Obstetrics and Gynecology (Society for Maternal-Fetal Medicine) (2021)
  5. Ursodeoxycholic acid versus placebo in women with intrahepatic cholestasis of pregnancy (PITCHES): a randomised controlled trial, The Lancet (2019)
  6. Intrahepatic cholestasis of pregnancy: Review of six national and regional guidelines, European Journal of Obstetrics & Gynecology and Reproductive Biology (2018)

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

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