Skip to content
Blood Test Tracker

Creatine Kinase (CK), Total

An enzyme found mostly in muscle. It leaks into the blood when muscle is strained or injured, so hard exercise is a common reason for a high result.

AI-verified against cited sources. Awaiting expert reviewAlso called CK, CPK, Total CKLOINC 2157-6

Check your result

Sex (optional)

The usual range for CK depends on sex. Choose female or male above to see where you stand.

Nothing you type here leaves your browser.

What it is

Creatine kinase (CK) is an enzyme that helps muscle cells make energy. Most of it sits inside skeletal muscle, with smaller amounts in the heart and brain. When muscle cells are strained or damaged, CK leaks into the blood and the level goes up. This test measures total CK, which adds up all forms of the enzyme. What is typical varies a lot with sex, age, muscle mass and ancestry.

Why it matters

CK gives a clue about whether muscle has been stressed or injured. Clinicians use it when someone has muscle pain or weakness, or to look into muscle side effects of some medicines. A mildly high result is very common and often comes from exercise or a naturally higher baseline. Very high results matter more, because muscle breakdown can strain the kidneys.

If it’s low

A CK below your lab's range is common and usually not a concern on its own. Levels tend to be lower in women, in older adults and in people with less muscle mass, and many healthy people sit near the bottom of the range.

Common causes

  • Less muscle mass or a smaller frame
  • Older age, when CK tends to drift lower, especially in men
  • Being female, since the usual range for women sits below the range for men

If it’s high

A high CK means more of the enzyme than usual has leaked out of muscle cells. Hard exercise, a naturally higher baseline and minor muscle injury are the most common reasons. The number alone can't show the cause, so your clinician will look at your symptoms, medicines and other tests.

Common causes

  • Hard, new or unfamiliar exercise, especially heavy lifting or downhill running (CK can stay high for several days)
  • A naturally higher baseline, which is more common in men, people with more muscle, and people of African ancestry
  • Muscle injury, such as a fall, surgery or a shot into a muscle
  • Some medicines, including statins, fibrates, some HIV medicines and angiotensin receptor blockers
  • An underactive thyroid (hypothyroidism)
  • Seizures
  • Muscle inflammation (myositis) or an inherited muscle condition such as muscular dystrophy
  • Chronic kidney disease
  • A heart attack, although other tests such as troponin are usually used for that now
  • Rhabdomyolysis, a rapid breakdown of muscle that is rare but serious, and usually comes with severe muscle pain, weakness or dark urine

What can help

  • Rest from intense exercise for several days, then ask your clinician whether to repeat the test
  • Return to hard workouts gradually after a break, since new or unfamiliar exercise can raise CK for days
  • Tell your clinician about every medicine and supplement you take, so they can judge whether one could be involved
  • Ask whether your thyroid and kidney function should be checked

Usual ranges

What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.

The usual range depends on sex and age. Choose women or men to see the one that applies.

Children and teens 10 ranges

See CK by age and sex, with the U.S. survey numbers where they exist.

If this applies to you

CK means a little more for some people. Open the one that fits you.

Endurance athlete

CK leaks out of muscle after hard training and races, so a high result is common in athletes. People who do a lot of hard training tend to run higher even at rest, and some people rise much more than others after the same session.

Blood tests for endurance athletes

High cholesterol or heart risk

CK is a muscle enzyme. The atorvastatin label asks people to report unexplained muscle pain, tenderness or weakness. The 2026 U.S. guideline suggests checking CK when muscle symptoms are severe, and notes that muscle aches with a normal CK are common on statins.

Blood tests for heart health and high cholesterol

Strength training

CK leaks from muscle after training, and resistance work, especially the lowering (eccentric) part of a lift, tends to raise it the most. A high CK after lifting is common, and some people rise far more than others after the same session.

Blood tests for strength training and bodybuilding

Taking isotretinoin

Some people doing vigorous exercise on isotretinoin have had raised CK, a muscle enzyme. The label says what this means isn't known, and muscle breakdown has been reported only rarely.

Blood tests on isotretinoin

How common is your level?

NHANES describes the US civilian, non-institutionalized population, not a 'healthy' reference group. People with disease, on medication, fasting or not (except fasting-subsample markers), smokers and so on are all included. A percentile says where a value sits among Americans of that sex and age, not whether it is normal.

How CK varies with age in the U.S.Shaded: middle 90% and middle 50% of people. Line: the median. U/L. Point at any age, or focus the chart and use the arrow keys, to read both sexes in words.

Use the left and right arrow keys to read each age. Shift moves five years.

Reference data derived from CDC/NCHS National Health and Nutrition Examination Survey (NHANES), cycles 2015-2016, 2017-March 2020 (pre-pandemic), August 2021-August 2023. Analysis by bloodtesttracker.com; not endorsed by CDC, NCHS or HHS.

Explore CK by age and sex: every percentile as a table, with a download.

What can affect your result

  • Recent exercise: hard workouts can raise CK for several days, with a peak anywhere from 1 to 5 days afterward
  • Sex: men usually run higher than women
  • Ancestry: people of African ancestry often have higher usual levels
  • Age: levels in men tend to fall over the years
  • Muscle mass and fitness level
  • Muscle injury, surgery and shots into a muscle
  • Medicines such as statins, fibrates and some HIV medicines
  • Hard exercise in the days before the draw can raise CK, and the rise can last several days.
  • Muscle injury, surgery, falls and shots into a muscle can raise CK.
  • Statins, fibrates, some HIV medicines and angiotensin receptor blockers can raise CK.
  • Grossly hemolyzed samples are rejected by labs such as Quest and ARUP.
  • Tubes with oxalate, fluoride or any anticoagulant other than heparin are rejected by labs such as Quest and ARUP.

After muscle injury CK starts to rise within hours, peaks in 1 to 3 days, then falls by roughly 40% a day once the injury stops.

When to talk to a clinician

Get care promptly for severe muscle pain, swelling or weakness, especially with dark, tea-colored urine or very little urine, or after extreme exercise, a crush injury, a long time lying on the floor, heat illness or a seizure. Doctors often define rhabdomyolysis as symptoms plus a CK above 1,000 U/L or more than 5 times the top of the lab's range. If you also have chest pain, trouble breathing, confusion or fainting, call 911 or your local emergency number.

Questions you could ask

  • Is this level typical for someone with my sex, age and background?
  • Could recent exercise or a minor injury explain this, and should we repeat the test after some rest?
  • Could any of my medicines or supplements be contributing?
  • Should my thyroid or kidney function be checked?

Questions people ask

Can a hard workout really raise my CK?

Yes. Hard workouts, especially lifting and downhill running, can raise CK for several days, and levels often peak between one and five days afterward. If your result is unexpectedly high, a clinician may suggest a few days of rest and a repeat test.

My CK is above the lab's range, but my clinician isn't worried. Why?

Lab ranges come from groups of people, and many healthy people sit above them. CK runs higher in men, in people with more muscle and in people of African ancestry. In one large US study, younger African American men had a typical (median) CK above the standard upper limit. Your clinician weighs the number against your symptoms and history.

What is the difference between CK and CK-MB?

Total CK adds up all forms of the enzyme. CK-MB is the form found mostly in heart muscle. Other tests, such as troponin, are usually used to check for heart injury now, so CK-MB is ordered less often than it once was.

Show the science and sources

Units

  • 1 U/L = 1 U/L
  • 1 U/L = 0.01667 µkat/L
  • 1 U/L = 16.67 nkat/L

Open the CK unit converter

Is a change real?

CK naturally varies about 14.5% from test to test in the same healthy person. Between two results from the same lab, a change of roughly 40% or more is unlikely to be day-to-day noise or lab variation (95% reference change value). Source: The European Biological Variation Study (EuBIVAS): a summary report.

For clinicians and researchers

CK is a dimer of M and B subunits. CK-MM is the main form in skeletal muscle and heart, CK-MB is concentrated in the heart, and CK-BB is found mostly in brain and smooth muscle. Any of them raises total CK, and macro-CK forms can too, which isoenzyme testing can separate. Quest measures total CK by spectrophotometry. After muscle injury CK begins to rise about 2 to 12 hours later, peaks at 24 to 72 hours, then falls by about 39% of the previous day's value each day (Ulster Med J 2021). Reference limits are method-, sex-, age- and ancestry-dependent. In a pooled analysis of 11,346 adults with high cholesterol, median CK was 135 U/L in African American men and 73 U/L in African American women, versus 64 and 42 U/L in white men and women (Neal 2009). In a Dutch population study of rested adults, the 97.5th percentile limits were 2 to 5 times higher than the assay manufacturer's limits, and 13% of white European, 23% of South Asian and 49% of Black participants had CK above the manufacturer's limits (Brewster 2007). Rhabdomyolysis is commonly defined as compatible symptoms with CK above 1,000 U/L or above 5 times the upper limit of normal; a statin-specific definition uses CK above 10 times the upper limit with renal impairment and muscle symptoms, or above 50 times the upper limit. In randomized trials, muscle symptoms without a raised CK were only slightly more common on a statin than on placebo (a difference of under 1%), and serious statin-related muscle injury is under 0.1% (AHA 2019). Labcorp lists a default critical limit of above 10,000 U/L; the Quest and ARUP test pages list none. Reference limits differ widely between labs (Quest, UW Medicine and Labcorp intervals for adult men all differ), so use the range on your own report.

LOINC 2157-6 (primary). Specimen: serum-or-plasma.

Sources

  1. Creatine Kinase (CK), Total (test code 374), Quest Diagnostics
  2. Creatine Kinase, Total, Serum or Plasma (test 0020010), ARUP Laboratories
  3. Relationship of ethnic origin, gender, and age to blood creatine kinase levels, The American Journal of Medicine (2009)
  4. Distribution of creatine kinase in the general population: implications for statin therapy, American Heart Journal (2007)
  5. Rhabdomyolysis: Revisited, Ulster Medical Journal (2021)
  6. Creatine-kinase- and exercise-related muscle damage implications for muscle performance and recovery, Journal of Nutrition and Metabolism (2012)
  7. Statin Safety and Associated Adverse Events: A Scientific Statement From the American Heart Association, Arteriosclerosis, Thrombosis, and Vascular Biology (2019)
  8. Approach to asymptomatic creatine kinase elevation, Cleveland Clinic Journal of Medicine (2016)
  9. Creatine phosphokinase test, MedlinePlus (National Library of Medicine)
  10. Critical (Panic) Values, Labcorp (2024)
  11. Creatine Kinase Total Activity (CK), UW Medicine Laboratory Test Menu

AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.

Related markers