ALT (alanine aminotransferase) is an enzyme found mainly in your liver cells. When those cells are damaged or inflamed, ALT leaks into your bloodstream, and a blood test picks up the elevated level. A high ALT result is a signal that something is irritating or injuring your liver, though the cause can range from something temporary and harmless to a condition that needs treatment.
What Counts as High
Normal ALT falls between 7 and 55 U/L for males and 7 and 45 U/L for females. Any result above your lab’s upper limit is technically elevated, but doctors pay close attention to how far above normal you are.
A mildly elevated ALT, less than twice the upper limit of normal (roughly under 90 to 110 U/L depending on sex), is extremely common and often prompts a simple retest rather than an immediate workup. Many mild elevations resolve on their own. Moderate elevations fall between two and 15 times the upper limit, and severe elevations exceed 15 times normal, which would mean ALT above roughly 675 to 825 U/L. The higher the number, the more urgently your doctor will investigate.
Common Causes of Elevated ALT
The single most common reason for a mildly elevated ALT in the United States is fatty liver disease (now called steatotic liver disease). Excess fat accumulates in liver cells and triggers low-grade inflammation, slowly pushing ALT up. This is closely tied to carrying extra weight, high blood sugar, and metabolic syndrome.
Other frequent causes include:
- Alcohol use. Regular or heavy drinking directly damages liver cells. In alcohol-related liver injury, a companion enzyme called AST often rises even higher than ALT. When the AST-to-ALT ratio exceeds 2 to 1, alcohol is a strong suspect.
- Viral hepatitis. Hepatitis B and C infections can cause both acute spikes and chronic low-level elevations.
- Medications and supplements. Statins, acetaminophen (Tylenol), certain antidepressants, NSAIDs like ibuprofen, blood pressure medications, and even herbal products like green tea extract and kava can raise ALT. These elevations are often asymptomatic and discovered incidentally. Drugs are far more likely to cause a quiet bump in liver enzymes than actual liver damage.
- Autoimmune hepatitis. The immune system mistakenly attacks liver cells, causing persistent inflammation.
- Iron overload. A genetic condition called hemochromatosis causes the body to absorb too much iron, which accumulates in the liver.
Less common but important causes include severe infections, blood clots affecting the liver’s blood supply, and rare metabolic disorders like Wilson disease, which causes copper to build up in the liver and can push AST dramatically higher than ALT (sometimes at a 4-to-1 ratio).
Symptoms You Might Notice
Mild ALT elevations usually produce no symptoms at all, which is why they’re typically caught on routine bloodwork. As liver inflammation worsens, symptoms can include fatigue, weakness, nausea, loss of appetite, and abdominal pain or swelling. More advanced liver damage may cause yellowing of the skin and eyes (jaundice), dark urine, pale stools, leg swelling, and persistent itching. If you’re experiencing any of these alongside a high ALT result, the situation is more urgent than an isolated lab finding.
What Happens After a High Result
For a borderline or mildly elevated ALT, the first step is usually repeating the test. A single high reading can reflect something as temporary as a strenuous workout, a recent illness, or a medication you just started. If the elevation persists, doctors typically order a hepatitis panel, iron studies, and an abdominal ultrasound. For mild cases, this initial round of testing is generally enough to identify or rule out the most common causes.
Moderate elevations may prompt additional testing for autoimmune conditions. Severe or massive elevations call for more urgent investigation, including screening for toxins and blood flow problems in the liver.
If the cause remains unclear or the numbers don’t improve, the next tier of evaluation includes advanced imaging and a test called transient elastography (FibroScan), which measures liver stiffness to estimate how much scarring or fat buildup is present. In some cases, a liver biopsy is needed to pin down a diagnosis, and referral to a liver specialist (hepatologist) becomes appropriate.
The AST-to-ALT Ratio
Your blood test likely included both ALT and AST (aspartate aminotransferase), a related liver enzyme. The ratio between them can point toward a cause. In most types of liver inflammation, ALT runs higher than AST. When AST climbs well above ALT, particularly at a ratio of 2 to 1 or higher, it suggests either alcohol-related liver disease or cirrhosis (advanced scarring). This ratio isn’t a diagnosis on its own, but it helps narrow the possibilities.
Lowering ALT Through Lifestyle Changes
Because fatty liver disease is the most common driver of elevated ALT, weight loss is the most effective lever for many people. The numbers are encouraging and specific: losing just 5% of your body weight can measurably reduce liver fat. Reaching a 7% loss can begin to reverse fatty liver disease itself. At 10% or more, inflammation may resolve and even some scarring can improve.
Diet matters in specific ways. Filling half your plate with non-starchy vegetables increases fiber and antioxidants that support liver health. Adding fatty fish like salmon and tuna, along with nuts, seeds, avocados, and olive oil, provides fats that benefit the liver. On the other side, reducing red meat, butter, cheese, and packaged foods containing trans fats helps. A practical guideline: keep saturated fat sources to no more than a palm-sized portion per day.
Exercise doesn’t require a dramatic commitment to start helping. Even five minutes of daily movement can begin to improve liver health over time, with the goal of gradually building to 150 minutes of moderate activity per week. If alcohol is a factor, reducing or eliminating it is the single most impactful change you can make.
If a medication is the suspected cause, your doctor may adjust the dose, switch to an alternative, or simply monitor your levels more frequently. Stopping a medication on your own without guidance can create other problems, so this is a conversation to have with whoever prescribed it.