What is ALT?

ALT is usually a good indicator of problems with the liver, but can you reduce your levels? Find out all you need to know about ALT.

What is ALT?

Alanine aminotransferase (ALT) is one of the two most clinically relevant aminotransferases in the liver cells (aspartate aminotransferase being the other). Aminotransferases are a group of enzymes primarily involved with amino acid (the building blocks of protein) metabolism.

ALT is released from the liver when liver cells are injured. And clinically, liver damage is therefore measured in the blood as serum ALT.

Why do I need an ALT blood test? 

Serum ALT may be requested by a doctor to investigate or monitor liver problems. Symptoms of liver damage can be wide-ranging and non-specific. In fact, in many cases, it can produce no symptoms at all.

However, symptoms of liver damage can include:

  • Loss of appetite
  • Nausea and vomiting
  • Skin itching
  • Tummy pain
  • Tummy swelling
  • Yellowing of the skin (jaundice)
  • Easy bruising
  • Swelling of the ankles or lower legs

Due to the asymptomatic nature of liver conditions (such as non-alcoholic fatty liver disease), often a serum ALT blood test would form a key part of initial medical investigations. However, sometimes ALT levels are within the normal range even if the liver is damaged, so this test alone can’t be used to rule out conditions like fatty liver.


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What’s a normal ALT level?

Generally, a normal serum ALT level is considered to be 5-38 IU/L for adult females and 10-50 IU/L for adult males, although exact reference ranges may vary between laboratories.

What causes a high ALT level?

Since ALT is released from the liver when injury to liver cells occurs, a raised serum ALT level may signal liver damage.

Common causes of a raised ALT level include:

  • Excess alcohol consumption – liver cell damage can be seen even at modest levels of alcohol consumption. To keep health risks from alcohol low, men and women are advised not to drink more than 14 units a week. If you are concerned about your drinking, a good first step is to speak with your GP. However, as well as the NHS, there are numerous charities across the UK that provide advice for individuals looking to cut down their alcohol intake.
  • Medications – this can include prescribed medications, herbal remedies, over-the-counter preparations, and supplements aimed at enhancing sporting performance.
  • Excess body fat – having a high body mass index (BMI) or excess weight around the middle can increase your risk of developing liver damage. A powerful way of treating obesity involves reducing your calorie intake and increasing your exercise. Exercise doesn’t always mean going to the gym - we’ve put together some other ways to move more to help you get started.
  • Non-alcoholic fatty liver disease – this is the most common cause of mild alteration of liver enzyme levels, including serum ALT, in the Western world. You can find more about NAFLD in our blog.

Additional causes of a raised serum ALT level can include:

  • Viral hepatitis
  • Autoimmune hepatitis
  • Haemochromatosis
  • Wilson's disease
  • Alpha1-antitrypsin deficiency
  • Coeliac disease
  • Strenuous exercise

Can a high ALT indicate cancer?

Well, it depends. When discussing the liver, a particularly relevant cancer is hepatocellular carcinoma which is a type of cancer that comes specifically from liver cells. Hepatocellular carcinoma tends to occur as a complication of liver cirrhosis (scarring of the liver). Important risk factors for the development of cirrhosis are alcohol misuse and chronic hepatitis, but it can include many of those causes of raised ALT highlighted above too.

One of the battery of tests that a doctor may do to investigate cirrhosis would include liver function blood tests, of which aminotransferases form a part. Therefore, in isolation and in the absence of certain risk factors a raised serum ALT probably does not indicate cancer. However, if an individual has an elevated serum ALT in the context of suspicious clinical features, then it may raise the possibility. If you are concerned about cancer then consult with your doctor.

What causes low ALT?

For the majority of individuals, a lower-than-normal serum ALT level is not a cause for concern and has little clinical relevance. It has been postulated that in certain groups of individuals, such as those with chronic kidney disease or those of old age, a low serum ALT is a marker for increased frailty. However, there is a lack of consensus on this.

How can I test my ALT level?

You can test your serum ALT from the comfort of your own home with our Liver Function Blood Test.

How can I lower my ALT levels?

  • One of the most effective things you can do to lower your serum ALT levels is to cut back on your alcohol consumption, especially if you are exceeding 14 units a week.
  • Next, quit smoking. If you want to quit but don’t know where to start, the NHS has a list of free services that can boost your chances of quitting smoking for good.
  • Is it time you try a ‘Couch to 5K’? Lowering your body fat percentage is another excellent way to improve your serum ALT levels.

Want to know more about how to improve your liver health? We’ve put together seven ways to keep your liver healthy.

What should I do if my ALT levels are abnormal?  

As you can see there is a spectrum of causes for a raised serum ALT, therefore, if you have ongoing concerns about your abnormal results, please speak to your doctor, to put this in context.

In our Medichecks blood test reports, we strive to deliver tailored, evidence-based health advice, based upon your biomarker levels - this is the same for your serum ALT if it is abnormal.


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  2. GP notebook. Aminotransferases. https://gpnotebook.com/en-gb/simplepage.cfm?&ID=1584070698&linkID=906 (accessed 26 March 2023).
  3.  Edoardo G. Giannini, Roberto Testa, Vincenzo Savarino. Liver enzyme alteration: a guide for clinicians. CMAJ 2005; 172(3).
  4.  National Collaborating Centre for Mental Health (UK). Alcohol-Use Disorders: Diagnosis, Assessment and Management of Harmful Drinking and Alcohol Dependence. The British Psychological Society & The Royal College of Psychiatrists 2011; 22624177(). https://pubmed.ncbi.nlm.nih.gov/22624177/ (accessed 26 March 2023).
  5. Jalili V, Poorahmadi Z, Hasanpour Ardekanizadeh N, Gholamalizadeh M, Ajami M, Houshiarrad A, Hajipour A, Shafie F, Alizadeh A, Mokhtari Z, Shafaei H, Esmaeili M, Doaei S. The association between obesity with serum levels of liver enzymes, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase and gamma‐glutamyl transferase in adult women. Endocrinol Diabetes Metab 2022; 5(6).
  6. NHS. Obesity. https://www.nhs.uk/conditions/obesity/ (accessed 26 March 2023).
  7. Peltz-Sinvani N, Klempfner R, Ramaty E, Sela BA, Goldenberg I, Segal G. Low ALT Levels Independently Associated with 22-Year All-Cause Mortality Among Coronary Heart Disease Patients. J Gen Intern Med 2016; 31(2).

Related tests

Liver Function Blood Test

Check your liver function and look for signs of liver damage or inflammation with our easy at-home finger-prick blood test

  • Results estimated in 2 working days
  • 7 biomarkers