A High AST with a High CK and a Normal ALT
AST is not only a liver enzyme. Muscle contains a great deal of it, and when muscle is the source the liver-specific enzyme beside it stays put. So a raised AST with a raised CK and a normal ALT points at muscle. Recognizing that stops the liver investigation that would otherwise follow: scans, hepatitis serology, and months of worry about a liver that is working normally.
The pattern on your report
- AST High · moderate Key
- CK High · marked Key
- ALT Normal Key
- GGT Normal Key
Printed as: ALT in U/L— Concentrated in the liver, so a normal value beside a raised AST is what points away from it.AST in U/L— Present in liver, heart and skeletal muscle, which is why it cannot locate the damage by itself.CK in U/L— Ranges differ substantially by sex and ancestry because they track muscle mass, and exercise makes a value uninterpretable for days.GGT in U/L
Why the numbers look like this
Enzymes leak into the blood from whichever tissue is being damaged, and their usefulness comes from where they are concentrated. ALT sits overwhelmingly in liver cells. AST sits in liver, heart and skeletal muscle. Creatine kinase sits in muscle almost exclusively.
So the combination reads as a location. Both aminotransferases up together points to the liver. AST up with CK up and ALT untouched points to muscle, because only muscle holds the first two without holding the third.
How long each stays up differs too. CK rises within hours of muscle injury, peaks over a day or two, and can stay raised for the best part of a week; AST usually settles sooner. A sample taken days after the event therefore catches the two at different points on their curves, which is why the balance between them is read loosely rather than exactly.
The amount of muscle involved determines whether this matters. A gym session produces a modest rise that resolves. Widespread muscle breakdown releases enough myoglobin to injure the kidney, which is the situation the red flags below are about.
Not being flagged is not the same as normal
CK reference ranges are among the least universal on any panel. Muscle mass drives the baseline, so ranges differ substantially by sex and by ancestry; normal values run higher in people of African ancestry, and that difference is about build and nothing else. Exercise raises it enormously and for days, so a value taken after a heavy session or a first return to the gym cannot be compared with a range at all. Where a genuine baseline is needed, the sample is taken after several days without strenuous activity.
What else on the report can hide this
GGT is the quickest way to confirm the liver is not involved, since it rises in most liver conditions that would raise AST and stays normal when muscle is the source. A normal ALT and a normal GGT together make a liver explanation very unlikely.
The history usually supplies the answer before any further test. Unaccustomed exercise, a fall, a long lie, an intramuscular injection, a seizure, or a recent viral illness each explain it, and each resolves.
Statins deserve a separate question because they are so widely taken. Most people on a statin with muscle aches do not have a raised CK, and most raised CK values on a statin are mild and do not require stopping the drug — but the combination of aches with a markedly raised CK does, and that distinction is better made than guessing at.
Thyroid function is the test most often forgotten here. An underactive thyroid raises CK and causes aches at the same time, which reads convincingly as a muscle disorder until the TSH comes back.
Where the rise is persistent with no exercise, no drug and a normal thyroid, an inherited muscle disorder comes into view, and that is a neurology question, not a repeat blood test.
What usually causes it
Listed from most to least common — not from most to least serious.
- Very common
Exercise
By far the commonest reason, and the rise can be striking after unaccustomed or eccentric work. It settles over days without strenuous activity.
- Very common
A fall, injury or intramuscular injection
From the history. Any bruised or crushed muscle releases both enzymes, and vaccinations count.
- Common
Statins
Common and usually mild. Aches with a markedly raised CK is the combination that changes management, not a mild rise on its own.
- Common
An underactive thyroid
Raises CK and causes aches simultaneously, so it imitates a muscle disorder. A TSH settles it and treatment resolves both.
- Common
A viral illness
Influenza and other viruses inflame muscle directly. Aching out of proportion to the illness, and it recovers with it.
- Common
Alcohol
Damages muscle as well as liver, so it can raise both AST and CK. A raised GGT alongside points to the liver being involved too.
- Uncommon
A seizure or a long period lying immobile
Sustained or prolonged muscle compression, and the rise can be large enough to threaten the kidney.
- Uncommon
Inflammatory muscle disease
Polymyositis and related conditions cause weakness rather than pain, particularly climbing stairs or reaching up. It needs specialist assessment.
- Rare
An inherited muscle disorder
A persistently raised CK with no exercise, no drug and a normal thyroid, sometimes with a family history. Referral rather than repetition.
- Rare
Rhabdomyolysis
Massive breakdown with dark urine and a risk of kidney injury. This is the emergency version and needs immediate assessment.
What is usually checked next
- GGT Normal alongside a normal ALT makes a liver source very unlikely, which is what stops the liver pathway.
- An activity and injury history for the preceding week Exercise, falls, injections and seizures account for most of these, and none needs a test.
- TSH An underactive thyroid raises CK and causes aches at once, and it is the cause most often overlooked.
- Repeat after several days without strenuous activity Establishes a genuine baseline, since exercise makes the value uninterpretable against any range.
- Kidney function and a urine dipstick if the CK is very high Myoglobin released from muscle can injure the kidney, and that is the risk worth acting on quickly.
When to seek care sooner
- Emergency Dark, cola-colored or red-brown urine
- Emergency Passing little or no urine
- Emergency Severe muscle pain and swelling, particularly after a long lie or collapse
- Emergency Chest pain
- Soon Weakness climbing stairs or reaching above the head
- Soon Muscle aches with a markedly raised CK while taking a statin
Questions worth bringing to your appointment
- Does my normal ALT mean this is muscle rather than liver?
- Had I exercised or been injured in the week before the test?
- Has my thyroid been checked?
- Should the test be repeated after a few days of rest?
- Given my statin, does this level of CK mean anything needs changing?