What is “AST (GOT)” in a Health Checkup? A Thorough Explanation of Causes for High Levels and the Risks of Leaving Them Untreated

“My health checkup results had a checkmark next to the AST (GOT) section…”

“I don’t have any particular symptoms, but is it okay to just leave it as is?”

Many of you may have thought this upon receiving your health checkup results.

The liver is known as a “silent organ,” and even when it sustains damage, subjective symptoms rarely appear. Therefore, blood test values like AST (GOT) are among the few “SOS signs” emitted by the liver. Understanding them correctly is the first step in protecting your future health.

In this article, a hepatologist (liver disease specialist) at Saito Clinic of Internal Medicine in Nishi-ku, Kobe, will explain in detail what AST (GOT) is, why its levels rise, and the serious risks of leaving these high values untreated.

We have also summarized the contents of this blog in a video, so please be sure to watch it as well.

■1. What is AST (GOT)? — An Enzyme that Signals Liver Damage

AST (GOT) is an abbreviation for an enzyme called aspartate aminotransferase. It exists primarily within liver cells and plays an important role in converting the nutrients (amino acids) we consume from our diet into energy.

Normally, AST stays inside the liver cells. However, if liver cells are damaged and destroyed for some reason, AST leaks out into the blood. In other words, a high AST level in the blood is a sign that liver cells are being destroyed.

Why Does It Need to Be Checked Together with “ALT (GPT)”?

In health checkups, AST is almost always listed alongside a value called “ALT (GPT)”. This is because AST is present not only in the liver but also in the heart muscle (myocardium) and skeletal muscles.

• ALT (GPT): Since it exists almost exclusively in the liver, a high ALT level strongly suggests a liver abnormality.
• AST (GOT): Because it is also found outside the liver, if only AST is high, it could indicate conditions like myocardial infarction or muscle diseases.

By comparing both values, doctors can more accurately infer where the cause of the damage lies.

■2. How to Read AST Levels? — The Balance with ALT is the Key

When it comes to AST and ALT levels, it’s not just about whether they are high or low; the balance of which one is higher is also crucial.

Balance of AST and ALT	Main Suspected Conditions
ALT > AST	Conditions where liver cell destruction continues relatively gradually, such as fatty liver and chronic hepatitis.
AST > ALT	Conditions where the disease is progressing, or rapid liver cell destruction is occurring, such as alcoholic hepatitis, liver cirrhosis, and liver cancer.

Generally, it is considered ideal for both AST and ALT to be at or below the standard reference value of 30 U/L. If the level exceeds 51 U/L, it is judged as “abnormal,” and a detailed examination by a hepatologist is recommended.

■3. What are the Main Causes of High AST?

Various hidden liver diseases can cause an elevation in AST levels.

① Fatty Liver (Alcoholic and Non-Alcoholic)

One of the most common causes is “fatty liver.” In addition to alcoholic fatty liver caused by excessive drinking, there is an increase in Metabolic dysfunction-Associated Steatotic Liver Disease (MASLD), where fat accumulates in the liver due to overeating, lack of exercise, and obesity, even in people who do not drink.

② Alcoholic Liver Disease

Long-term excessive drinking directly damages liver cells during the alcohol breakdown process, causing AST to rise.

③ Viral Hepatitis

Infection with the Hepatitis B or Hepatitis C virus causes inflammation in the liver, destroying liver cells and leading to elevated levels.

④ Other Causes

Various other causes are possible, such as medication side effects (drug-induced liver injury) or autoimmune hepatitis, where the immune system mistakenly attacks the patient’s own liver.

■4. The Risks of Ignoring High AST Levels — Scary Because It’s a “Silent Organ”

The greatest risk of leaving high AST levels untreated is that the disease can progress to a severe stage without any subjective symptoms.

For example, in the early stages of a fatty liver, it is possible to return to a normal liver by improving lifestyle habits. However, if left untreated and the burden on the liver continues, there is a danger that it will progress to irreversible, serious diseases:

Fatty Liver → Hepatitis (such as MASH) → Liver Cirrhosis → Liver Cancer

Once it progresses to cirrhosis or liver cancer, treatment becomes extremely difficult. Being pointed out for “high AST” in a health checkup is a golden opportunity to care for your liver before it’s too late.

■5. If an Abnormality is Pointed Out in a Health Checkup, Get a Detailed Examination by a Hepatologist

If an AST abnormality is pointed out during a health checkup, please do not be complacent just because you have no symptoms. Be sure to consult a gastroenterologist, particularly a hepatologist (liver specialist).

Under the care of a hepatologist, they will first perform detailed blood tests to investigate the cause of hepatitis and conduct an abdominal ultrasound (echo) examination. An ultrasound is an extremely important examination that allows doctors to visually confirm directly—without putting a burden on your body—whether fat has accumulated in the liver, whether it has become hard (signs of cirrhosis), or whether a tumor has formed.

At our clinic, a hepatologist certified by the Japan Society of Hepatology will analyze your numbers from multiple angles and utilize ultrasound examinations to accurately diagnose the condition of your liver.

AST (GOT) is an important sign emitted by your “silent organ.” While various causes such as fatty liver, alcohol, and viruses can be behind the high numbers, the biggest risk is ignoring it due to a lack of subjective symptoms, which can lead to serious diseases like cirrhosis and liver cancer.

An abnormal value in a health checkup is not a declaration of illness, but an important “trigger” to protect your body. Please do not overlook this sign, and by all means, consult us, your liver disease specialists.