ALT (SGPT)

What is ALT (SGPT)?

ALT, short for alanine aminotransferase and formerly known as SGPT, is an enzyme found mostly inside liver cells. It is involved in the conversion of amino acids and in producing the sugar that the body uses for energy. It is also found in small amounts in the kidneys, heart and muscles, but most of the ALT in the blood comes from the liver. Because ALT levels can rise even before liver damage causes symptoms, it serves as an early warning sign.

When liver cells are damaged by causes such as inflammation, fat accumulation, toxic substances or viruses, ALT passes into the blood and its blood level rises. Because of this, ALT is considered one of the most specific routine tests for liver cell damage. In the laboratory, ALT activity in the serum sample is calculated by measuring how much reaction the enzyme carries out within a given time.

When is an ALT test ordered?

ALT is one of the tests most frequently ordered to assess liver health and is usually run as a panel together with AST, ALP, GGT and bilirubin. Because liver problems in the early stages usually cause no complaints, the test is also valuable for screening people who are overweight, have diabetes or drink alcohol regularly. In people diagnosed with chronic hepatitis or fatty liver, it is repeated regularly to monitor the course of the disease and the response to treatment.

• Weakness, nausea, loss of appetite or pain in the upper right abdomen
• Yellowing of the eyes or skin and dark urine
• Suspected fatty liver related to excess weight, diabetes or insulin resistance
• Monitoring of viral infections such as hepatitis B or hepatitis C
• Conditions that require long-term drug treatment, such as tuberculosis or rheumatic diseases

How do I prepare for an ALT test?

Fasting is not required for an ALT test, and blood can be given at different times of day; still, if it is ordered together with other liver tests, the morning may be preferred. Avoiding alcohol the day before the test and avoiding heavy exercise that strains your muscles helps the result reflect your actual condition. A light breakfast usually does not change the ALT result, but if your doctor has asked you to fast, follow that instruction.

Some painkillers, antibiotics, epilepsy medications, cholesterol medications and various herbal teas or supplements can affect ALT levels. It is therefore important to tell your doctor about all the medications and products you use; do not stop any medication unless your doctor advises you to. The blood needed for ALT is a small sample drawn from an arm vein, and a nurse can take it at your home or workplace.

What does an ALT result mean?

High ALT indicates damage to liver cells. Today the most common cause is fatty liver associated with excess weight and insulin resistance; viral hepatitis, alcohol, side effects of medications and herbal products, autoimmune liver diseases and bile duct problems can also raise the value. Very high values usually suggest acute hepatitis or sudden toxic damage. In acute infections such as hepatitis A, the value can rise very high within a short time and fall again with recovery.

The degree of ALT elevation does not always reflect the severity of the disease; even in advanced cirrhosis, the value may be normal or only mildly elevated. ALT results below normal usually do not point to a disease. In the case of a mild, one-off elevation, your doctor may repeat the test and, if needed, order further investigations such as hepatitis markers or an ultrasound. The upper limit for ALT can vary with age, sex and the laboratory's method; the range shown on this page belongs to the laboratory that analyzes your test. Your result should be interpreted by your doctor together with your symptoms and your other liver tests.