ALT Raised with a Normal AST and Bilirubin
An isolated ALT rise with a normal AST, bilirubin and ALP is the most common abnormal liver result on a routine panel. In adults, the most common explanation for this combination is metabolic fat accumulation in the liver. But a medicine or an over-the-counter supplement will produce it too, and so, less typically, will a hard workout in the days before the draw.
The pattern on your report
- ALT High · mild Key
- AST Normal Key
- Bilirubin Normal Key
- ALP Normal Supporting
Printed as: ALT in U/L— Also printed as SGPT on some reports.ALP in U/L— One notation worldwide. Some reports label it ALKP or ALP.AST in U/L— Also printed as SGOT on some reports.Bilirubin in umol/Lor mg/dL— These are not interchangeable figures: a value in mg/dL is roughly one seventeenth of the same result in umol/L, so a report from another country can look alarming until it is converted.
Why the numbers look like this
ALT and AST are enzymes that sit inside cells and reach the bloodstream when those cells are irritated or leak. Both are present in the liver and in skeletal muscle, in different proportions: ALT is more concentrated in the liver, while AST is far more abundant in muscle and is also found in red blood cells. Neither belongs to the liver alone. It is that difference in proportion that makes the balance between them informative. An ALT rise with a normal AST points towards the liver rather than muscle, without ruling muscle out.
Nearly all mild isolated ALT rises turn out to have an unremarkable cause, and many settle on their own once whatever provoked them stops.
Not being flagged is not the same as normal
The upper limit printed on most reports was derived from populations that included people with undiagnosed fatty liver, so it sits higher than the thresholds many liver specialists now work to: around 30 U/L for men and 20 U/L for women. A result of 45 can print unflagged and still be worth explaining.
What else on the report can hide this
Creatine kinase is what separates a liver source from a muscle one. Raised alongside ALT, it suggests the enzymes came from muscle, and timing matters for the same reason: a heavy training session in the days before the draw can lift both. Iron studies showing a high transferrin saturation point somewhere else again.
What usually causes it
Listed from most to least common — not from most to least serious.
- Very common
Metabolic dysfunction-associated steatotic liver disease (MASLD)
The default explanation when it comes with a raised waist circumference, raised triglycerides, low HDL, raised HbA1c or blood pressure. ALT typically sits above AST. If drinking is also significant, the two overlap, which the 2023 nomenclature calls MetALD.
- Common
Medications and supplements
Statins, acetaminophen, some antibiotics, and the ones most often missed: bodybuilding and herbal supplements. Ask specifically about anything that did not come from a prescription.
- Common
Alcohol
Classically pushes AST above ALT, roughly a 2:1 ratio. An ALT-dominant picture makes alcohol a less likely sole explanation, though it still contributes.
- Common
Recent strenuous exercise
A heavy lifting session or long run in the preceding days lifts both enzymes, usually AST more than ALT and CK with them, so an ALT-only rise is the less typical shape after exercise. Repeat after a week of rest.
- Uncommon
Chronic viral hepatitis B or C
Worth excluding once, by serology, in anyone with a persistent unexplained rise, and regardless of the number in anyone born in, or whose parents were born in, East Asia, sub-Saharan Africa or parts of Eastern Europe, where chronic hepatitis B is many times more common. Frequently silent for years.
- Uncommon
Celiac disease or thyroid dysfunction
Both produce transaminase rises that resolve when the underlying condition is treated.
- Rare
Hemochromatosis, autoimmune hepatitis, Wilson disease or alpha-1 antitrypsin deficiency
Iron studies with a high transferrin saturation, autoantibodies, a low ceruloplasmin in someone under 40, or a low alpha-1 antitrypsin level. Considered when the common causes have been excluded: rare, treatable, and costly to miss.
What is usually checked next
- Repeat liver function tests after 2-4 weeks avoiding alcohol, supplements and heavy exercise Tells a one-off rise from a persistent one, and it is the most useful single next step.
- CK Identifies a muscle rather than liver source.
- Hepatitis B and C serology Excludes chronic viral infection.
- FIB-4 score Uses age, AST, ALT and platelets to estimate fibrosis risk and decide who needs imaging or referral.
- Transient elastography (FibroScan) The next step when the FIB-4 is not low: it measures liver stiffness directly and decides between reassurance and referral.
- Liver ultrasound Supports a diagnosis of fatty liver and looks for other structural causes such as bile duct dilatation or a mass. It cannot confirm steatosis on its own: its sensitivity falls away when the fat content is mild, and it cannot grade fibrosis.
When to seek care sooner
- Emergency You have taken more paracetamol (acetaminophen) than the label allows, even spread across a day or two
- Emergency Confusion or drowsiness alongside abnormal liver results
- Same day Yellowing of the eyes or skin, or dark urine
- Same day ALT more than ten times the upper limit of normal
- Mention it A rise that persists across three panels over six months
Questions worth bringing to your appointment
- Could this be explained by exercise or a supplement, and should we simply repeat it after a washout?
- What is my FIB-4 score, and does it suggest I need imaging?
- Have I ever been tested for hepatitis B and C?
- If this is fatty liver, what change would you expect to move the number, and by when?