Optimal Liver Enzymes: What ALT and AST Should Actually Be

Quick answer

Optimal ALT (SGPT) is under 25 U/L for women, and under 30 U/L for men. This is based on research linking these levels to the lowest heart and metabolic risk. The standard upper limit of 40 was set decades ago, and it includes many people with early, silent fatty liver. A value of 25 to 40 often points to early fatty liver, known as NAFLD.

How the standard ALT range came to be

The standard upper limit for ALT, about 40 U/L, comes from older studies of "healthy" people. That group included people with silent fatty liver they did not know they had. So the "normal" range ended up too wide.

Newer research links ALT levels to real outcomes, like heart events. This research supports a tighter target.

The evidence behind a lower target

A landmark study

One well known study tested ALT in blood donors. Doctors screened out liver disease, high weight, alcohol use, and metabolic issues first. The truly healthy upper limit turned out to be about 30 for men, and 19 for women. That is roughly half the standard cutoff.

How common is fatty liver?

Fatty liver, known as NAFLD, affects an estimated 1 in 4 adults worldwide. It is even more common in Asian populations. Most cases are silent. They show up only through imaging, or a "borderline" enzyme result. The 25 to 40 zone is often exactly where fatty liver hides.

What the outcomes show

ALT in the 25 to 35 range is linked to higher heart and metabolic risk. Risk keeps rising as ALT climbs. The best outcomes appear at ALT under 20.

The Asian context

Asian adults tend to develop fatty liver at a lower body weight than Western groups. Fat stored around the belly is the main driver. In an Asian adult, an ALT of 25 to 35 more often means fatty liver.

Optimal ranges for each liver marker

ALT (SGPT)

• Optimal: under 25 for women, under 30 for men.
• Borderline: 25 to 40 for women, 30 to 40 for men.
• Mild rise: 40 to 80.
• Moderate rise: 80 to 200.
• Significant rise: above 200.

AST (SGOT)

AST (called SGOT on most Philippine lab reports) is less specific to your liver. It also comes from muscle and heart tissue. It usually tracks with ALT in liver disease. A high AST compared to ALT, more than double, suggests alcohol as the cause.

GGT

The optimal target is under 25 U/L. GGT is the most sensitive marker for alcohol, some medicines, and metabolic syndrome. High GGT alongside high ALT often points to fatty liver or alcohol.

Alkaline phosphatase, or ALP

The standard range is 40 to 130 U/L. This marker reflects bile flow and bone health. High ALP alongside high bilirubin suggests a bile flow problem.

Bilirubin

The total range is 0.1 to 1.2 mg/dL. The "direct" portion is more specific to bile flow problems.

Albumin

The standard range is 3.5 to 5.0 g/dL. This shows how well your liver makes protein. It drops with serious liver disease, poor nutrition, or inflammation.

What causes a mildly high ALT, in the 25 to 40 range

Fatty liver, by far the most common cause

This is driven by belly fat, refined carbs, sugar, and insulin resistance. It often comes with high GGT, triglycerides, and fasting insulin. It responds well to lifestyle change. Blood sugar tends to drift up alongside it, and the optimal HbA1c target is tighter than the usual lab cutoff.

Alcohol use

This tends to raise GGT the most. It also raises the AST to ALT ratio. Red blood cell size, called MCV, is often high too.

Medicine

Statins usually cause a mild rise tied to dose. Acetaminophen, many antibiotics, and some herbal supplements can raise ALT too.

Recent hard exercise

This causes a short lived rise. Avoid intense exercise for 48 hours before a blood test.

Recent illness

Viral infections, including mono and COVID, can raise ALT for a while.

Viral hepatitis

Hepatitis B and C are worth checking with any unexplained rise. Both are common enough in the Philippines to check for.

Less common causes

Autoimmune liver disease, a genetic iron overload called hemochromatosis, and a rare copper buildup called Wilson disease can raise ALT too.

Fatty liver: the main driver behind a mildly high ALT

Fatty liver disease is now one of the most common liver conditions in the world. It is rising fast alongside metabolic syndrome.

Here is how it tends to progress:

1. Simple fatty liver. Fat builds up without much inflammation. ALT is mildly high. This stage is fully reversible.
2. A more active stage. Fat plus inflammation. ALT runs higher. Some risk of moving forward.
3. Scarring, called fibrosis. How much this can reverse depends on the stage.
4. Cirrhosis. Heavy scarring, with limited reversal.
5. Liver cancer. A late stage complication.

Most adults with a mildly high ALT are in stage 1. This stage is fully reversible with lifestyle change. Catching it early is where you get the most benefit.

How to lower a high ALT

For fatty liver, the most common cause, these changes help most.

1. Cut refined carbs and sugar

This is the single biggest lever, especially sweetened drinks, which directly add fat to your liver.

2. Lose fat around your belly

Losing 5 to 10% of your body weight often brings ALT back to normal. Belly fat matters more than total weight.

3. Move regularly

Both cardio and weight training help reduce liver fat.

4. Cut back on alcohol

A high GGT alongside high ALT often points to alcohol as a contributing cause.

5. Try a Mediterranean style diet

This has the strongest diet evidence for reversing fatty liver.

6. Keep drinking coffee, if you already do

Regular coffee is linked to better liver health in long term studies.

7. Choose supplements carefully

Vitamin E has some evidence in confirmed advanced cases. Omega 3 has a modest effect. Milk thistle has weak evidence. Most other "liver detox" supplements are not well supported.

For advanced cases

A newer medicine, resmetirom, was recently approved for a more advanced stage of fatty liver with scarring. Other medicines are still in development.

How fast can you expect change?

After a real change in habits:

• Triglycerides: 4 to 8 weeks.
• ALT: 8 to 12 weeks.
• GGT: 4 to 8 weeks.
• Imaging changes, like an ultrasound or a liver elastography scan: 3 to 6 months.
• Deeper tissue healing: 6 to 12 months.

Most fatty liver driven ALT rises get better within 12 weeks of real effort.

When to see a doctor

Talk to a doctor, or a liver specialist, if:

• ALT is above 100.
• ALT stays above 40 despite 12 weeks of real lifestyle change.
• You test positive for hepatitis B or C.
• You have a significant history of drinking.
• Liver disease runs in your family.
• You notice signs of advanced disease, like yellow skin, belly swelling, or easy bruising.
• Imaging shows real scarring.

See how a &you Labs panel checks your liver, including ALT, AST, GGT, and more.

Frequently asked questions

What does SGPT mean in a blood test?

SGPT is the older name for ALT, a liver enzyme. Philippine labs still print SGPT on most reports, so the two mean the same thing. A result of 25 to 40 is often early fatty liver, even though the lab calls it normal. The healthy target is under 25 for women and under 30 for men.

Is SGOT the same as AST?

Yes. SGOT is the older name for AST. It comes from your liver, but also from muscle and heart tissue. That is why doctors read it next to SGPT rather than on its own.

My ALT is 32. Should I worry?

This sits in the borderline zone. Early fatty liver is the likely cause, especially with belly fat, refined carbs, or drinking. Try 12 weeks of lifestyle change, then retest.

How well does ALT catch fatty liver?

Not perfectly. Some people have fatty liver with a normal ALT. Others have a high ALT from a different cause. Imaging can confirm the diagnosis when needed.

Can fatty liver be fully reversed?

In the earliest stage, yes, often fully. In the more active stage, partial to full reversal is common with real effort. With real scarring, reversal is slower. With cirrhosis, it is limited.

Why is my GGT high but my ALT normal?

This is common with alcohol use, certain medicines, and early metabolic syndrome. A high GGT alone is still worth paying attention to.

Should I take "liver detox" supplements?

Most have weak evidence. Coffee, omega 3, and a Mediterranean style diet all have more support than most detox products.

Key takeaways

• Optimal ALT is under 25 for women, and under 30 for men. The standard cutoff of 40 is too loose.
• Most mild ALT rises in adults today come from fatty liver, which is reversible with lifestyle change.
• Always check ALT alongside AST, GGT, and metabolic markers like triglycerides and fasting insulin.
• Hepatitis B is common enough in the Philippines to check alongside any unexplained liver enzyme rise.
• Most fatty liver driven ALT rises improve within 12 weeks of real effort.