Liver Function Test

Non-alcoholic fatty liver disease (NAFLD) is a spectrum of liver conditions — from simple fat accumulation in liver cells (steatosis) to NASH (non-alcoholic steatohepatitis, where inflammation accompanies the fat) to cirrhosis. It is the most common liver condition in the UK, strongly associated with obesity, diabetes, and metabolic syndrome. ALT and GGT are the most sensitive routine blood markers for early NAFLD, though they can be normal even when liver fat is present. A mildly elevated ALT (above 35 IU/L in men, above 25 IU/L in women) in the context of risk factors warrants further investigation, including liver ultrasound.

GGT (gamma-glutamyl transferase) is an enzyme involved in glutathione metabolism. Alcohol is a potent enzyme inducer — it upregulates the microsomal enzymes involved in its own metabolism, including GGT. As a result, even moderate regular alcohol consumption can significantly elevate GGT levels. GGT typically returns to normal within 2 to 8 weeks of alcohol abstinence, making it a useful marker for monitoring compliance with alcohol reduction. Unlike ALT and AST, which require actual cell damage, GGT can be elevated purely from enzyme induction without hepatocyte injury.

Elevated ALT without obvious explanation (covert liver disease) has a wide differential including: non-alcoholic fatty liver disease (extremely common in people with obesity or metabolic syndrome); medication-induced liver injury (statins, methotrexate, anti-epileptics, some supplements, and herbal remedies); alcohol (even reported alcohol intake often underestimates actual consumption); unrecognised viral hepatitis (particularly hepatitis C, which can be asymptomatic for decades); thyroid disease (hypothyroidism can cause mild ALT elevation); and muscle damage from intense exercise (elevated AST and CK, with normal GGT). Your physician report will help distinguish these patterns.

The impact depends on the amount and pattern of consumption. GGT is the most sensitive early marker — it rises with regular moderate drinking before ALT becomes elevated. ALT and AST typically rise when there is actual hepatocyte injury, which occurs with heavier consumption (particularly binge drinking) or chronically elevated intake over years. Stopping or significantly reducing alcohol for 4 to 6 weeks and retesting allows a clear picture of alcohol’s contribution — GGT will fall markedly within 4 weeks if alcohol is the primary cause. This abstinence test is a useful and actionable clinical intervention.

Mild, isolated ALT elevations (up to 3 times the upper reference limit) are common on statins and usually clinically insignificant — large-scale trials have shown statin-related hepatotoxicity is extremely rare. If ALT is elevated above 3 times the upper limit, most guidelines recommend stopping the statin and investigating the cause before restarting. This panel provides the baseline LFT against which any changes on statin therapy can be monitored. If your GP has prescribed a statin and wants baseline liver monitoring, or if you want to monitor liver health while on a statin, this panel is an appropriate tool.

Albumin is produced exclusively by the liver and has a half-life of around 20 days, meaning it only falls significantly when liver synthetic function has been impaired for a sustained period. Low albumin is therefore a marker of chronic liver disease, cirrhosis, or severe hepatic impairment — not acute liver damage. It can also be low in malnutrition, nephrotic syndrome (where albumin is lost in the urine), or chronic inflammatory states. A mildly low albumin in an otherwise healthy individual may reflect poor nutritional intake rather than liver disease. Your physician will interpret albumin in the context of all six liver markers together.