Alanine Aminotransferase (ALT)

July 21, 2020

What is Alanine Aminotransferase (ALT)?

Alanine aminotransferase or ALT is an enzyme located primarily in the liver and kidneys. The level of ALT in the blood is usually low, however, a rise in serum levels is indicative of liver damage. A high level of ALT can usually be detected before obvious signs of liver injury occur, such as jaundice.[1]

Why take an ALT blood test?

An ALT blood test is used to screen for liver disease or injury. It measures the amount of ALT in the blood. Increased serum levels of ALT may also confirm muscle damage if there is an absence of symptoms which may indicate liver damage.[2] ALT along with aspartate aminotransferase (AST) are the most commonly used biomarkers in the clinical diagnosis of liver damage.[3]

ALT levels increase when the liver is damaged potentially because of alcohol abuse, medication use, cirrhosis, muscle injury, kidney damage, liver infection as well as trauma. Therefore, if you are concerned about the health of your liver you may choose an ALT blood test. Equally, if you have recently experienced muscle damage your ALT levels may be raised.

You can test your ALT levels by purchasing a simple at-home finger prick test kit which is then analysed at an accredited lab. Forth offers a number of blood tests which include albumin such as a liver function test which can be purchased for just £39.00.

What function does ALT have in the body?

ALT is an important enzyme in gluconeogenesis, a process whereby glucose is made from non-carbohydrate carbon substrates like lactate, glycerol and pyruvate. ALT is widely distributed around the body, mainly being found in the liver and kidneys but is also present in the muscles, heart, pancreas and lungs.[4]

ALT catalyses the transfer of an amino group from alanine to alpha-ketoglutarate which makes pyruvate and glutamate which can be used to produce energy as part of the gluconeogenesis pathway.[5]

Because ALT can be found in abundance in the liver, it is a good indicator of liver (hepatic) injury. When liver cells become damaged or injured, ALT leaks into the bloodstream. There are several factors which may be responsible for this including infections like hepatitis, injury or alcohol abuse.

​How do changes in ALT affect health and wellbeing?

Increased ALT levels mean individuals are at a greater risk of obesity, type II diabetes and cardiovascular morbidity. They also usually occur alongside high triglycerides and fat in the liver, known as liver steatosis.[6] Therefore, individuals who lead a sedentary lifestyle are at an increased risk of high levels of ALT and thus metabolic diseases. As a result, high ALT levels increase the risk of depression, anxiety, weight gain and low energy.

If you are worried about your ALT level or just want to check where you fall on the range, you can test your level with a simple at-home blood test.

What Can Cause ALT To Change?

ALT levels increase due to injury to the liver which may include trauma but also infection and illness. Infections such as acute hepatitis will increase ALT levels significantly because the liver will release ALT into the bloodstream.

A moderate rise in ALT can be caused by chronic hepatitis or the causes of a fatty liver such as alcohol intake, diabetes or raised triglycerides. However, ALT levels can remain near to normal if liver cirrhosis or cancer is present or if the bile ducts are blocked.

If you are worried about your ALT level or just want to check where you fall on the range, you can test your level with a simple at-home blood test.

What Are The Most Common Symptoms Of Liver Damage?

The most common symptoms of liver damage are:

  • Feeling tired and weak all or most of the time
  • Reduced appetite
  • Loss of libido
  • Jaundice (yellowing of the skin and whites of the eyes
  • Itchy skin
  • Nausea and/or vomiting[7]

How to keep ALT in the healthy range

Fatty liver disease is one cause of increased ALT levels where the accumulation of excess fat in the liver causes it to become damaged. A fatty liver is associated with obesity and so it is important to implement and maintain a healthy lifestyle. Essentially making the right lifestyle choices will help to keep your ALT levels within a healthy range.

Diet is a major factor in the health of the liver. The functions of the liver include the detoxification of chemicals, metabolism of drugs and to filter the blood coming from the digestive tract. Fructose, a type of sugar has been shown to be consumed in larger quantities by people who have fatty liver disease. Therefore, it is advisable to monitor your sugar intake, particularly fructose. Research has shown a diet high in vegetables and low in animal-based protein can improve ALT activity and help keep levels within a normal range.[8]

Alcohol also impacts on the health of the liver and as a result, can increase ALT levels if it causes damage to the organ. If body mass index increases (BMI) increases then the activity of liver enzymes including ALT also rises.[9] To maintain a healthy liver, alcohol consumption should be limited and kept within guidelines of no more than 14 units per week.[10]

Leading a sedentary lifestyle is a risk factor for many diseases which, in turn, can also lead to an increase in serum ALT levels. Participation in physical activity can reduce the risk of diabetes by 35% and cardiovascular disease by 49%. Plus, losing just 5% body weight and exercising regularly is associated with a significant improvement in fatty liver disease.[11]

- Health scores calculated



[1] Lab Tests Online. (2017). Alanine Aminotransferase (ALT). Available at:

[2] Nathwani, R, A et al. (2005). Serum Alanine Aminotransferase in Skeletal Muscle Diseases. Hepatology: 41(2), pp 380-382.

[3] McGill, M, R. (2016). The Past and Present of Serum Aminotransferases and the Future of Liver Injury Biomarkers. EXCLI. J: 15, pp 817-828.

[4] Marshall, W. (2012). Alanine Aminotransferase (Serum, Plasma). Association for Clinical Biochemistry. Available at:

[5] Ray Kim, W et al. (2008). Serum Activity of Alanine Aminotransferase (ALT) as an Indicator of Health and Disease. Hepatology: 47(4).

[6] Danielsson, J et al. (2014). Impacts of Common Factors of Life Style on Serum Liver Enzymes. World Journal of Gastroenterology: 20(33), pp 11743-11752.

[7] National Health Service. (2017).  Liver Disease. Available at:

[8] Iwamoto, M., Yagi, K and Sato, M. (2013). Eating a Healthy Lunch Improves Serum Alanine Aminotransferase Activity. Lipids Health Dis: 12.

[9] Alatalo, P, I., Kivisto, H, M., Hietala, J, P., Puukka, K, S., Bloigu, R and Niemelä, O, J. (2008). Effect of Moderate Alcohol Consumption on Liver Enzymes Increases with Increasing Body Mass Index. The American Journal of Clinical Nutrition: 88(4), pp 1097-1103.

[10] National Health Service. (2018).  Alcohol Units. Available at:

[11] Webb, D. (2018). Diet and Nutrition for Liver Health. Today’s Dietitian: 20(6), p 36.

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This information has been medically reviewed by Dr Nicky Keay

Nicola has extensive clinical and research experience in the fields of endocrinology and sport and exercise medicine. Nicky is a member of the Royal College of Physicians, Honorary Fellow in the Department of Sport and Exercise Sciences at Durham University and former Research Fellow at St. Thomas' Hospital.

Dr Nicky Keay

Dr Nicky Keay

BA, MA (Cantab), MB, BChir, MRCP.