Liver Function Tests: ALT, AST, GGT, and Bilirubin Explained

Quick answer

A liver function panel checks ALT, AST, GGT, alkaline phosphatase, bilirubin, albumin, and total protein. Most Philippine lab reports print ALT as SGPT and AST as SGOT. ALT is the most sensitive marker for damaged liver cells. GGT is the most sensitive to alcohol, medicines, and metabolic problems. Both markers often drift toward the edge of their healthy target range long before they cross into the "abnormal" flag. That drift is where the most useful early warning sits.

ALT (alanine aminotransferase)

What it measures: an enzyme that leaks out when liver cells get damaged.

On your lab sheet: ALT (called SGPT on most Philippine lab reports). The two names mean the same test.

The lab's normal range: up to 40 U/L, though some labs use up to 56 U/L. The healthy target range: below 25 for women, below 30 for men.

Why it matters: ALT is the most specific marker for liver cell damage. An ALT of 30 to 40 U/L still counts as normal. But it is often linked to fat in the liver that shows up on a scan. By the time ALT crosses the standard flag above 40, fatty liver has often already set in.

Common causes of a high ALT:

• Fatty liver.
• Drinking alcohol.
• Certain medicines, such as statins, too much paracetamol, or some antibiotics.
• Hepatitis B or C.
• Extra weight, or a poor response to insulin.

AST (aspartate aminotransferase)

What it measures: a liver enzyme that is also found in muscle, the heart, and red blood cells.

On your lab sheet: AST (called SGOT on most Philippine lab reports).

The lab's normal range: up to 40 U/L.

The AST-to-ALT ratio matters:

• AST higher than ALT, with a ratio above 1. This often points to alcohol-related liver disease, advanced scarring, or muscle damage.
• ALT higher than AST, the more typical pattern, points to fatty liver or hepatitis.

GGT (gamma-glutamyl transferase)

What it measures: an enzyme found in the liver and bile ducts.

The lab's normal range: up to 60 U/L. The healthy target range: below 25 U/L.

Why it matters: GGT is very sensitive to alcohol, even a moderate amount. It also rises with heavy medicine use, metabolic problems, fatty liver, and bile flow issues. A GGT that stays high with a borderline ALT is one of the earliest signs of a liver under stress.

Alkaline phosphatase (ALP)

The lab's normal range: 44 to 147 U/L, though this varies by lab.

Why it matters: a high ALP can point to a bile flow problem or bone disease. It can also reflect normal life stages, like growing children or pregnancy. Your doctor reads it with your other results.

Bilirubin

Total bilirubin normal range: 0.2 to 1.2 mg/dL. Direct bilirubin normal range: below 0.3 mg/dL.

• High total bilirubin with a normal direct level often points to Gilbert's syndrome, a common and harmless condition. It can also mean red blood cells are breaking down faster than normal.
• A high direct level points to a blockage in bile flow or a liver problem.
• A large rise causes jaundice, a yellowing of the skin and eyes, and needs a doctor's review.

Albumin and total protein

Albumin normal range: 3.5 to 5.0 g/dL. Total protein normal range: 6.0 to 8.3 g/dL.

Low albumin can signal advanced liver trouble, serious inflammation, protein loss through the kidneys, or poor nutrition. High total protein can point to ongoing inflammation.

Common liver patterns

Pattern 1: Early fatty liver, the most common pattern among Filipinos

• ALT (SGPT) between 25 and 55 U/L.
• GGT between 25 and 60 U/L.
• AST normal or borderline.
• Often paired with high triglycerides, high fasting insulin, and rising HbA1c.
• Extra weight carried around the belly.

This stage can be fully undone with weight loss and a change in diet.

Pattern 2: Alcohol-related liver stress

• AST higher than ALT, often more than double.
• GGT high, often disproportionately so.
• Often paired with a high MCV on a complete blood count.

Pattern 3: Medicine-related liver stress

A recent new medicine, with both ALT and AST high. This often settles down once the medicine is stopped, under a doctor's guidance.

Pattern 4: Viral hepatitis

ALT that is much higher than normal, often above 100. This needs a hepatitis B and C blood test to confirm.

Pattern 5: Gilbert's syndrome, a harmless condition

• Only total bilirubin is high.
• The direct part and every other liver marker stays normal.
• No treatment is needed.

Why fatty liver matters

Fatty liver moves through stages:

1. Simple fat buildup. Fat sits in the liver without inflammation, and there are no symptoms.
2. A more active stage. Fat plus inflammation, which can move forward if untreated.
3. Scarring. Also called fibrosis.
4. Advanced scarring. Also called cirrhosis, and it cannot be undone.
5. Liver cancer or liver failure. The final stage.

The best time to act is stage 1 or 2. That is when your markers sit close to the line, not way past it. This is why the healthy target range matters more than a single red flag.

How to improve your liver markers

• Lose weight. Losing 7 to 10 percent of your body weight often reverses simple fat buildup.
• Cut back on refined carbs and added sugar. Sugar, especially fructose, is a major driver of liver fat.
• Cut back on or stop alcohol.
• Move more. Both cardio and strength training help.
• Try omega-3 fats. They offer a modest benefit.
• Coffee. Moderate coffee drinking is linked to lower liver enzyme levels.
• Manage your metabolic health. Improving how your body responds to insulin also improves your liver.

Most people see measurable improvement within 12 to 24 weeks of lifestyle change.

When to see a doctor sooner

• ALT or AST that stays more than twice the normal upper limit.
• High bilirubin with a normal complete blood count.
• Jaundice, meaning yellow skin or eyes.
• Levels that stay high despite 12 weeks of lifestyle change.
• New pain in the upper right belly, severe tiredness, or weight loss you cannot explain.

The next steps often include a hepatitis blood test and a scan, such as an ultrasound. Sometimes a specialist referral follows.

Curious what your own liver markers look like? A &you Labs panel includes ALT, AST, GGT, bilirubin, albumin, and total protein as standard. Each result is read against both the lab range and the healthy target range.

Frequently asked questions

What does SGPT mean in a blood test?

SGPT is just another name for ALT. Philippine labs print SGPT on the report, while most global guides say ALT. It is a liver enzyme that leaks into your blood when liver cells get hurt. A high SGPT most often points to fat in the liver.

Is SGOT the same as AST?

Yes. SGOT and AST are the same test under two names. Philippine labs tend to print SGOT. Your doctor reads it next to your SGPT, since the two together hint at the cause.

Do I need to fast for a liver panel?

Not strictly. But most labs draw it at the same time as cholesterol and blood sugar tests. Those do need fasting. One morning fasting draw covers everything.

Can liver enzymes rise after one night of heavy drinking?

Yes. GGT, ALT, and AST can rise for a short time after drinking alcohol. Skip alcohol for 48 hours before your draw to get the most accurate baseline reading.

Are slightly high liver enzymes always a problem?

Not always, and that is why the healthy target range matters. An ALT of 35 still counts as in range. But it sits at the upper end where many adults with fatty liver fall. The trend across several tests matters more than any single reading.

Will my liver heal if I make changes?

Early fatty liver can be undone. More scarring can level off and even improve with steady effort. Cirrhosis cannot be undone, but it can be slowed.

Should I ask for a liver elastography scan if my liver markers are borderline?

A liver elastography scan, sometimes called transient elastography, is a painless scan. It checks liver stiffness and fat without surgery. It is a reasonable next step if your ALT, AST, or GGT stays high along with other metabolic risk factors.

Key takeaways

• ALT is the most specific marker for liver cell damage. GGT is the most sensitive to alcohol, medicines, and metabolic stress.
• Most early fatty liver disease shows up as a borderline-normal ALT and GGT, not as a dramatic spike.
• The AST-to-ALT ratio helps point to the likely cause.
• Fatty liver can be undone in its early stages.
• The healthy ALT target is below 25 for women or below 30 for men. That is well below the standard flag at 40.