CK blood test
Creatine kinase
In short
A typical adult CK result is 26 to 192 U/L for women and 39 to 308 U/L for men. A mild rise is common after exercise or a minor muscle injury and usually settles within a week. Very high levels need prompt care, since severe muscle breakdown can harm the kidneys. Always read your result against the range printed on your own report.
An enzyme that leaks from muscles after hard use or injury.
CK is an enzyme found mainly in muscles, with smaller amounts in the heart and brain. When muscle is strained or damaged, CK leaks into the blood. A hard workout can raise it for several days, so doctors often ask about recent exercise.
Is my CK high or low?
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Typical range
| For | Range | Unit |
|---|---|---|
| Female | 26–192 | U/L |
| Male | 39–308 | U/L |
Typical ranges for adults. Labs differ a little, so the range printed next to your result is the one to go by.
If your CK is high
A mild rise is common after exercise or a minor muscle injury and usually settles within a week. Very high levels need prompt care, since severe muscle breakdown can harm the kidneys.
Common reasons
- Hard exercise, especially weights or long runs, in the days before
- An injection into a muscle, a fall or a minor muscle injury
- Naturally higher levels in people with more muscle or African ancestry
- Some cholesterol medicines, which can affect muscles in some people
- An underactive thyroid
- Less often: severe muscle breakdown, a muscle disease or heart muscle injury
If your CK is low
A low CK is common and rarely a concern.
Common reasons
- Less muscle, which often comes with older age or little activity
- Normal variation between people
- An overactive thyroid
- Some steroid medicines
What can throw it off
Hard exercise, a fall or an injection into a muscle can raise CK for several days.
When it can’t wait
A CK of 10000 U/L or more usually needs a doctor's attention the same day. Call your doctor’s office, or their after-hours line. If you feel very unwell, call your local emergency number.
Questions to take to your appointment
- 1Could my recent exercise or an injury explain this?
- 2Should I repeat the test after a week without hard exercise?
- 3Could any of my medicines be affecting my muscles?
Read together with
Doctors rarely read CK alone. These usually sit next to it.
- ASTAn enzyme found in the liver, muscles and heart.
- ALTAn enzyme that lives mostly inside liver cells.
- CreatinineA waste product from muscles that the kidneys clear.
- PotassiumA mineral salt (electrolyte) that keeps your heartbeat and muscles steady.
- TSHA brain hormone that tells the thyroid how hard to work.
Quick answers
What is the CK blood test?
CK (Creatine kinase): An enzyme that leaks from muscles after hard use or injury. CK is an enzyme found mainly in muscles, with smaller amounts in the heart and brain. When muscle is strained or damaged, CK leaks into the blood. A hard workout can raise it for several days, so doctors often ask about recent exercise.
What is a normal CK level?
For most adults, CK is typically 26 to 192 U/L for women and 39 to 308 U/L for men. Labs differ a little, so the range printed next to your result is the one to go by.
What does a high CK mean?
A mild rise is common after exercise or a minor muscle injury and usually settles within a week. Very high levels need prompt care, since severe muscle breakdown can harm the kidneys. Common reasons include hard exercise, especially weights or long runs, in the days before; an injection into a muscle, a fall or a minor muscle injury; naturally higher levels in people with more muscle or African ancestry; and some cholesterol medicines, which can affect muscles in some people. A doctor reads it together with your other results and how you feel.
What does a low CK mean?
A low CK is common and rarely a concern. Common reasons include less muscle, which often comes with older age or little activity; normal variation between people; an overactive thyroid; and some steroid medicines.
What can affect my CK result?
Hard exercise, a fall or an injection into a muscle can raise CK for several days.
When is my CK result urgent?
A CK result of 10000 U/L or more usually needs a doctor's attention the same day. Call your doctor's office or their after-hours line. If you feel very unwell, call your local emergency number.
What should I ask my doctor about my CK?
Questions worth taking to the appointment: Could my recent exercise or an injury explain this? Should I repeat the test after a week without hard exercise? Could any of my medicines be affecting my muscles?
What this page can’t do
It reads each number on its own.
Doctors read results together — ALT with AST, ferritin with hemoglobin, TSH with free T4. A pattern says more than any single flag.
It doesn't know you.
Your age, your medicines, how you feel and your last result all change what a number means.
It doesn't remember.
Close this page and your results are gone. That's on purpose: nothing was ever sent to us.
We also make Vita: Health Coach, an app for those parts. It reads your whole report with your medicines and history in mind, answers follow-up questions in plain words, and keeps your reports in one place — for you and for the people you look after.
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