ALT
Also known as: Alanine Aminotransferase, SGPT
What Does ALT Measure?
ALT (Alanine Aminotransferase), also known as SGPT (Serum Glutamic-Pyruvic Transaminase), is an enzyme found primarily in liver cells. A blood test measuring ALT detects how much of this enzyme has leaked into the bloodstream. Under normal conditions, ALT stays inside liver cells where it helps convert proteins into energy. When liver cells are damaged or inflamed, they release ALT into the blood, causing levels to rise above the normal range.
Why Does ALT Matter?
ALT is one of the most specific and sensitive indicators of liver health available through a standard blood test. Elevated ALT levels can signal a wide range of liver conditions — from mild, temporary inflammation caused by medications or alcohol, to serious diseases like hepatitis, non-alcoholic fatty liver disease (NAFLD), or cirrhosis. Because the liver performs over 500 vital functions including detoxification, protein synthesis, and metabolism, early detection of liver damage through ALT monitoring is critical for preventing irreversible organ damage. ALT is routinely included in comprehensive metabolic panels (CMP) and liver function tests (LFTs), making it a frontline screening tool in primary care.
Normal Ranges
Males
7–56 U/L (units per liter)
Females
7–45 U/L (units per liter)
Children
Varies by age; generally 7–45 U/L, with infants having slightly higher ranges
Causes of High Levels
- Non-alcoholic fatty liver disease (NAFLD) — the most common cause of mildly elevated ALT in developed countries
- Alcoholic liver disease — excessive alcohol consumption directly damages liver cells and releases ALT
- Viral hepatitis (Hepatitis A, B, or C) — viral infections cause significant liver inflammation and cell death
- Medication or supplement toxicity — acetaminophen overdose, statins, NSAIDs, and certain herbal supplements can elevate ALT
- Celiac disease — intestinal inflammation can cause secondary liver enzyme elevation
- Intense or prolonged physical exercise — strenuous workouts can temporarily raise ALT due to muscle breakdown
Causes of Low Levels
- Chronic kidney disease — reduced enzyme production has been associated with renal insufficiency
- Vitamin B6 (pyridoxine) deficiency — ALT requires vitamin B6 as a cofactor, so deficiency can lower measured levels
How to Improve Your ALT
Diet
- Reduce or eliminate alcohol consumption, as alcohol is directly hepatotoxic and one of the most impactful dietary changes for liver health
- Follow a Mediterranean-style diet rich in vegetables, legumes, whole grains, olive oil, and lean fish to reduce liver fat and inflammation
- Limit added sugars and high-fructose corn syrup, particularly from sodas and processed foods, which drive non-alcoholic fatty liver disease
- Increase intake of cruciferous vegetables (broccoli, Brussels sprouts, cauliflower) which support liver detoxification pathways
- Consume coffee (2–3 cups/day) — multiple studies show regular coffee consumption is associated with lower ALT and reduced liver fibrosis risk
Supplements
- Milk thistle (Silymarin) 140–420 mg per day — has evidence for reducing liver inflammation and protecting liver cells from toxins
- Vitamin E 800 IU/day — shown in clinical trials (PIVENS trial) to significantly reduce ALT in non-diabetic adults with NAFLD
- Omega-3 fatty acids (EPA/DHA) 2–4 g/day — help reduce liver fat accumulation and lower ALT in fatty liver disease
- N-acetylcysteine (NAC) 600–1200 mg/day — a precursor to glutathione that supports liver detoxification and cell protection
Related Biomarkers
Frequently Asked Questions
What does it mean if my ALT is slightly elevated?
A mildly elevated ALT (typically 1–3 times the upper limit of normal) is common and does not always indicate serious disease. Common causes include fatty liver disease, recent intense exercise, alcohol consumption, or certain medications. Your doctor will likely recommend repeating the test and may order additional liver function tests to investigate the cause. In many cases, lifestyle changes such as dietary improvements and weight loss can bring ALT back to normal.
How high does ALT need to be to indicate liver damage?
ALT levels more than 3 times the upper limit of normal (above approximately 135–168 U/L depending on the lab) are generally considered significantly elevated and warrant further investigation. Levels 10 times or more above normal (over 500 U/L) often indicate acute liver injury such as viral hepatitis, drug toxicity, or ischemic hepatitis. However, even mildly elevated ALT sustained over time can reflect progressive liver disease, so any persistent elevation should be evaluated by a physician.
Can exercise cause high ALT levels?
Yes, intense or prolonged physical exercise — particularly resistance training, long-distance running, or high-intensity interval training — can temporarily raise ALT levels due to muscle cell breakdown releasing enzymes into the bloodstream. This is usually a short-term elevation that resolves within 3–7 days of rest. If your ALT was measured shortly after strenuous exercise, your doctor may recommend repeating the test after a few days of rest to get a more accurate baseline reading.