Blood test LFT fasting: what to know

An LFT is a group of blood measurements that can give information about liver irritation, bile flow, and how the liver is making proteins. Results are read together rather than as a diagnosis from one value. A recent illness, alcohol, medicines, supplements, exercise, or dehydration can affect interpretation. Abnormal results can occur for several reasons and do not by themselves identify one condition.

Check whether your request includes glucose or lipid testing, since those tests may have separate fasting instructions. If fasting is requested, ask whether plain water is allowed and when you should stop food. Do not stop prescribed medicines unless the clinician who ordered the test tells you to. Tell the phlebotomist about medicines, supplements, recent alcohol, and illness. Bring the request and arrive hydrated if water is permitted.

Contact a clinician promptly for yellowing of the skin or eyes, very dark urine, pale stools, severe upper-abdominal pain, repeated vomiting, unusual confusion, or marked drowsiness. These symptoms need assessment regardless of whether you were fasting. If you feel faint during or after the blood draw, tell staff immediately and sit or lie down.

Ask which tests are included, whether fasting is needed, whether your usual medicines should be taken, and when results will be reviewed. Ask what follow-up would be considered if one result is outside the laboratory range.