What is a normal AST level?
Up to about 34 to 50 U/L for adults, varying by lab. It’s not always your liver. In one study of men new to weights, an hour’s lifting kept it up a week or more.
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What is a normal AST level?
There’s no single UK range. Each lab sets its own top limit for adults, and it runs from about 34 to 50 U/L. U/L stands for units per litre.
| NHS lab | Normal adult AST |
|---|---|
| Royal Cornwall Hospitals | 5 to 34 U/L, aged 19 and over |
| North West London Pathology | 40 U/L or less, over 1 month old |
| North Bristol (Severn Pathology) | Below 50 U/L for men, below 35 U/L for women |
Sources: Royal Cornwall Hospitals; North West London Pathology; North Bristol NHS Trust
So a man with an AST of 45 is in range in Bristol, but above the limit in Cornwall. Always read your result against the range printed beside it.
Just over? UK liver doctors say a result should only be read alongside your past results and health history.
Ask your GP how it compares with your last test.
What is an AST (SGOT) blood test?
AST (aspartate aminotransferase) is an enzyme, a protein that does a job inside your cells. SGOT is another name for the same test.
AST is found mainly in your liver, heart, muscles, kidneys and red blood cells. When liver cells are hurt or die, they release it into your blood.
Think of AST as a smoke alarm wired into several rooms. It tells you there’s smoke, but not which room. That’s why it’s read next to your other results before anyone blames your liver.
| Where | What can raise AST |
|---|---|
| Liver | Liver cells being hurt or dying. |
| Muscles | Hard exercise, such as weightlifting, or muscle inflammation (myositis). |
| Heart | A heart attack. |
| Kidneys and red blood cells | Diseases of these tissues. |
Sources: Royal Cornwall Hospitals; BSG guideline; Pettersson 2008
Its partner, ALT, is more specific to the liver. Some labs, such as North Bristol, list AST as not routinely available, so you may only see ALT.
Have both? Read the ALT blood test guide next.
Why is my AST high if my liver is fine?
Often, the other source is your muscles. AST is plentiful in muscle, so hard use can push it up.
In one study, 15 healthy men who didn’t usually lift weights did a 1-hour weightlifting session. Their AST and ALT rose and stayed raised for at least 7 days.
The researchers said hard muscle work like weightlifting should be thought of as a cause of raised liver tests in people with no symptoms.
It was a small study of men new to lifting. It can’t tell you how much your own session matters. It does show why your GP needs to know.
Trained hard in the week before your test? Tell your GP, and see exercise before a blood test.
Normal AST levels by age
| Age | Normal AST (U/L) |
|---|---|
| 1 to under 7 | 26 to 55 |
| 7 to under 12 | 22 to 41 |
| 12 to under 19, girls | 17 to 33 |
| 12 to under 19, boys | 18 to 40 |
| 19 and over | 5 to 34 |
Source: Royal Cornwall Hospitals
Babies under 1 month can read higher still. North West London allows up to 80 U/L.
At all three labs above, adults have one range whatever their age. Age may still matter for women.
A German lab looked at over 1.3 million blood samples. The share of women with a raised AST rose from about 6% to 12% at around age 50.
For ALT and AST side by side, see liver enzyme levels by age.
What does a high AST mean?
It means something needs a look, not what it is. UK liver doctors say how far a result is out is not necessarily a guide to how much it matters.
They still advise thinking about a check for the cause whatever the level, and however long it’s been out of range.
What UK liver guidelines advise after an abnormal result
- 1
Look back
Read it with your past results and health history.
- 2
Liver screen
A tummy scan and blood tests for hepatitis B and C, iron and immune causes.
- 3
Scarring check
For fatty liver or no clear cause: a FIB-4 score from age, AST, ALT and platelets.
- 4
Next step
A second test or a specialist, depending on the score.
Source: BSG guideline
- Below 1.3 scoreLow risk of advanced scarring.
- 1.3 up to 3.3 scoreA second test, such as an ELF blood test or a Fibroscan (both check for liver scarring).
- Above 3.3 scoreAbove 3.25: think about a specialist clinic.
Source: BSG guideline
Over 65? The low-risk score is below 2.0 instead.
Your AST and ALT also count as a pair. In adults with abnormal liver tests, AST higher than ALT can be a clue to advanced scarring (fibrosis or cirrhosis), the guideline says. That holds even when both are in range.
That’s why it’s built into scarring scores like FIB-4. It’s one clue for your GP to weigh, not an answer on its own. AST may also be a more sensitive sign of liver injury from alcohol.
What to do about a high AST
- Ask your GP how your AST compares with your past results.
- Tell your GP if you trained hard in the week before your test.
- Ask whether your ALT was tested too.
- Drink no more than 14 units a week, spread over 3 or more days.
- Try to keep to a healthy weight.
- Ask about hepatitis A and B vaccines if you’re at risk.
Sources: BSG guideline; Pettersson 2008; NHS: liver disease; NHS: alcohol units
The NHS says regularly drinking just over the recommended levels can harm your health. See alcohol before a blood test and the fatty liver blood test.
When to speak to a GP
Most types of liver disease do not cause any symptoms in the early stages. So feeling well doesn’t rule it out. Speak to a GP if:
- Your skin or the whites of your eyes look yellow. Ask for an urgent GP appointment or call NHS 111. You may also have itchy skin, darker pee and paler poo.
- You feel very tired and weak all the time, lose your appetite or weight, lose your sex drive, have itchy skin, or feel or are sick. These can be symptoms of cirrhosis.
- You think you might have liver disease.
- Your AST is above your lab’s range. UK guidelines advise thinking about a check for the cause, whatever the level.
For the other lines on your results, see the liver function test guide and the GGT blood test.