Hepatic panel
Alanine aminotransferaseALT
Liver-specific aminotransferase; the most useful single marker of hepatocyte injury.
Sample
Serum
Clinical reference range
7 to 35 U/L
Adult male
Conv: 7–35 U/LFunc: 10–25 U/L
Biology
What it measures
Catalyzes alanine + α-KG ↔ pyruvate + glutamate. Highly concentrated in hepatocytes; cytoplasmic. Half-life ~47 h.
Clinical use
Why we order it
Detect and monitor hepatocellular injury, screen for NAFLD.
Lens · Clinical
Interpretation by lens
Clinical interpretation
Persistent ALT elevation >6 months warrants full chronic-liver-disease workup including viral serologies, autoimmune markers, ferritin, ceruloplasmin, alpha-1 antitrypsin, and ultrasound.
Functional interpretation
Functional optimal <25 U/L; values 25–40 are common in early NAFLD that mainstream cutoffs miss.
Research note
AASLD 2023 NAFLD/MASLD guidelines lowered diagnostic thresholds and emphasize FIB-4 + elastography over ALT alone.
Differential
Causes of abnormal values
Causes of HIGH
- ↑NAFLD/MASLD (most common worldwide)
- ↑Alcohol (typically AST > ALT)
- ↑Viral hepatitis A/B/C
- ↑Drug-induced liver injury (acetaminophen, statins, methotrexate, isoniazid)
- ↑Autoimmune hepatitis
- ↑Hemochromatosis, Wilson's, α1-antitrypsin
- ↑Celiac disease
- ↑Skeletal muscle injury (less than AST)
Causes of LOW
- ↓Vitamin B6 deficiency (cofactor)
- ↓Chronic kidney disease
Pitfalls
Pre-analytic & interpretation traps
- !ALT 'upper normal' (35–40 U/L) is too lenient — modern thresholds are <30 (men) and <19 (women).
- !Normal ALT does not exclude advanced NAFLD with fibrosis.
Follow-up orders
Logical next-step labs
Evidence-graded claims
What the data says
B
Lower upper-normal ALT thresholds (<30M/<19F) catch more clinically relevant disease
Prati 2002 and AASLD support.
A
Statin-induced ALT elevations <3× ULN do not require statin discontinuation
FDA and major lipid guidelines.
Related