What is ALT in a blood test and what do results mean
ALT (Alanine Aminotransferase) is a liver enzyme measured in blood work to assess liver health. Normal ALT blood test levels are about 10–40 U/L in men and 7–35 U/L in women. High levels of ALT in a blood test suggest liver irritation or damage, while low values are usually not clinically significant. Understanding what is ALT in lab results helps detect liver problems early.
Contents
Result interpretation ALT
What your result means based on common reference ranges
ALT levels within range indicate stable liver function without active inflammation or hepatocellular injury.
Mildly elevated ALT levels suggest chronic liver stress such as fatty liver or medication-related liver irritation.
Severely elevated ALT levels indicate acute liver injury, hepatitis, or toxic damage requiring urgent clinical evaluation.
Low ALT levels are generally benign and may reflect normal variation or vitamin B6 deficiency without liver disease.
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What is ALT?
ALT is an intracellular enzyme primarily located in hepatocytes, making it a key marker in liver blood test evaluation. When liver cells are damaged by inflammation, toxins, or metabolic stress, ALT levels rise in the bloodstream. It is commonly measured alongside AST, bilirubin, and ALP as part of liver function tests. Elevated ALT levels are associated with conditions such as fatty liver disease, hepatitis, or medication-related injury. In clinical practice, ALT blood test UK standards are used to monitor liver health, detect early disease, and evaluate treatment response.
Reference ranges
Causes of abnormal values
Causes of low ALT
- • Vitamin B6 deficiency — reduced enzyme synthesis lowers measurable ALT activity
- • Chronic kidney disease — altered metabolism decreases circulating ALT levels
- • Smoking — associated with reduced baseline ALT due to metabolic effects
Causes of high ALT
- • Non-alcoholic fatty liver disease (NAFLD) — fat accumulation causes chronic hepatocyte inflammation
- • Viral hepatitis (B or C) — immune-mediated liver cell destruction increases ALT release
- • Alcohol use — direct hepatotoxic effect damages liver cells
- • Medications (statins, paracetamol) — drug-induced liver stress elevates enzyme levels
- • Intense physical exercise — muscle breakdown contributes to transient ALT elevation
- • Gallstones — bile duct obstruction creates back pressure and liver irritation
ALT in combination with other markers
Possible symptoms
- •Fatigue and weakness
- •Jaundice (yellow skin or eyes)
- •Right upper abdominal pain
- •Dark urine
- •Nausea or reduced appetite
When to see a doctor
Consult a doctor if ALT levels are persistently above 100 U/L or exceed 200 U/L in a single test. Seek prompt evaluation if elevated ALT is combined with jaundice, abdominal pain, or worsening symptoms.
What to do if abnormal
- Repeat test in 2–4 weeks to confirm persistence
- Review medications and supplements with a doctor
- Reduce or stop alcohol intake completely
- Improve diet by lowering sugar and saturated fats
- Increase physical activity to reduce liver fat
The information on this page is intended for general understanding of test results and does not replace medical consultation. Accurate interpretation requires considering other blood markers and individual factors.
Content is based on medical literature and used within the PulseBook analytical system.
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