Creatine Kinase (CK)
Creatine kinase (CK) is an enzyme found mainly in muscle cells. A CK test helps identify muscle injury, inflammation or strain. Levels can rise after exercise, physical work, illness or certain medicines. CK is used in general health checks, when investigating muscle symptoms and during the review of some long term medications.
What the CK Test Measures
CK reflects the amount of muscle enzyme released into the bloodstream. It is found in:
- Skeletal muscle
- Heart muscle
- Brain tissue
Most routine CK testing focuses on skeletal muscle changes rather than heart or brain causes.
Why the CK Test Is Used
A CK test can help identify:
- Muscle inflammation
- Muscle injury from exercise or strain
- Medication effects (for example, statins)
- Viral illness affecting muscle tissue
- Rhabdomyolysis (when CK is extremely high)
- Muscle fatigue or weakness with no clear cause
CK may also be used for monitoring if you take medicines that can occasionally affect muscle enzymes.
Common Reasons to Have a CK Test
This test may be recommended if you have:
- Muscle aches or cramps
- Weakness or reduced strength
- Dark urine after intense exercise
- Unexplained muscle pain
- Recent heavy physical activity
- Concerns about medicine-related muscle symptoms
CK is also checked in some general health assessments when muscle symptoms are present.
Understanding CK Patterns
Raised CK
Often linked to exercise, strain, injury, viral illness or statin use. Levels can rise significantly after intense activity.
Very high CK
May indicate more significant muscle damage. Further assessment is needed depending on symptoms.
Mildly raised CK
Common and often temporary. Hydration, rest and repeat testing may be advised.
Low CK
Usually not clinically significant.
How the Test Is Performed
A small blood sample is taken from a vein in your arm. No fasting is required. Results are typically available within 24 to 48 hours.
When to Discuss CK Results with a GP
Speak to a GP if:
- CK levels are raised and you have muscle symptoms
- You take medicines that may affect muscle enzymes
- You experience weakness, cramps or unexplained aches
- Symptoms persist after rest or hydration
A GP can help interpret CK results and plan next steps.
Related Tests
CK is often reviewed alongside:
For a wider overview of routine blood markers, you can visit our main Blood Tests section in the Knowledge Base.
If you would like to discuss CK results or symptoms related to muscle health, you can book an online GP appointment for clear and personalised advice.
Last reviewed by Dr Zamiel Hussain, GMC registered GP
Updated: 8 December 2025