abnormal liver blood tests (lfts): structured primary care approach

Abnormal liver blood tests are common and often incidental. A high-yield approach is pattern-based (hepatocellular vs cholestatic vs isolated bilirubin) + risk factor assessment + a core aetiology screen when abnormalities persist or are clinically significant.

• Hepatocellular: ALT/AST predominant (e.g., NAFLD/MASLD, alcohol, viral hepatitis, drug-induced).
• Cholestatic: ALP (± GGT) predominant (e.g., biliary obstruction, PBC, PSC, infiltrative disease).
• Isolated bilirubin: consider Gilbert syndrome, haemolysis, fasting, or early hepatobiliary disease.

• Symptoms: jaundice, pruritus, RUQ pain, weight loss, fevers, fatigue, easy bruising, confusion (encephalopathy).
• Drugs/supplements: statins, antibiotics, antiepileptics, herbal products, anabolic steroids; check timing vs onset.
• Alcohol: quantify units, pattern, binges; look for AST:ALT ratio >2 (suggestive but not diagnostic of alcohol-related injury).
• Metabolic risk: BMI/waist, T2D, dyslipidaemia (NAFLD/MASLD is common).
• Exposure: viral hepatitis risk, travel, transfusion history, IVDU, sexual exposure.

Repeat timing: if mild elevation (<2× ULN) with a plausible transient trigger (e.g., intercurrent illness, new medicine) you can repeat in 4–12 weeks with safety-netting. Persistently abnormal results should trigger structured investigation.

• Bloods: FBC, INR, albumin, bilirubin, ALT/AST, ALP, GGT.
• Viral hepatitis: HBsAg, anti-HBc, anti-HCV (then PCR if positive) where risk/clinical suspicion.
• Autoimmune: AMA (PBC), ANA/SMA, IgG (autoimmune hepatitis) if pattern suggests.
• Iron overload: ferritin + transferrin saturation (haemochromatosis).
• Causes to remember: coeliac disease (especially with transaminitis), thyroid disease, muscle injury (check CK if very high AST).
• Ultrasound if persistent abnormalities, cholestatic pattern, or suspected fatty liver/structural disease (local pathways vary).

• Fibrosis risk in NAFLD/MASLD: consider non-invasive scores such as FIB-4 (age, AST, ALT, platelets) and/or local elastography pathways.
• Urgent referral / same-day: jaundice with systemic illness, suspected acute liver failure (INR rising, encephalopathy), very high transaminases with severe symptoms, biliary obstruction with cholangitis features (Charcot triad).
• Specialist referral: persistent unexplained LFT derangement, cholestatic pattern with positive AMA, hepatitis markers positive, abnormal synthetic function (INR/albumin), imaging abnormalities, or high fibrosis risk.

Rule of thumb: “abnormal numbers + abnormal function” (INR/albumin/platelets) = escalate.