Bile acids

Fasting and non-fasting ranges differ; some labs print an upper limit of 6 for fasting samples and up to 14 for random ones, and pregnancy uses the lab's own printed cut-offs.

Bile acids are made by the liver from cholesterol and released into the gut to help digest fat, then reabsorbed and recycled. Only a small amount is normally in the blood between meals. A rise means bile is not flowing freely from the liver or the liver is not clearing recycled bile acids from the blood. The test measures the total amount in a blood sample.

It is most often requested in pregnancy when there is itching, as part of looking into a condition where bile flow slows. Outside pregnancy doctors use it in some liver conditions and when other liver tests are unclear.

• Bile flow problems in pregnancy
• Blockage of the bile ducts
• Liver conditions including hepatitis and cirrhosis
• A meal before the test, because bile acids rise after eating
• Some medicines that slow bile flow

• It has no meaningful lower limit; a low value is the usual state in the general population
• Medicines that bind bile acids in the gut

• Eating within a few hours of the test raises the level
• Fasting and random ranges are different and a random value can sit above a fasting cut-off without meaning
• Different lab methods give different numbers

Many labs ask for a fasting sample, though in pregnancy a random sample is often used. Note on the report whether it was fasting.

Written by a UK consultant physician. Typical UK adult reference ranges; your laboratory's own printed range takes precedence.