Creatine Kinase (CK)
Creatine kinase (CK) has a wide, right-skewed distribution in US adults, and its median is higher in males than in females in every age group.
Unit: U/L · 22 slices · age and sex; race/ethnicity and sex · 1 source
Filed under panels: Muscle Enzymes · topics: Metabolic
Creatine kinase (CK) is an enzyme found mainly in skeletal muscle, with smaller amounts in heart muscle and brain. NHANES measured it in serum as part of the standard biochemistry profile. These percentiles describe the full US adult population, not a screened healthy group or a clinical laboratory interval. The pages show CK by age and sex, and separately by race and Hispanic origin and sex.
Population Distribution
By age
By race and ethnicity
Browse by Demographic
By age
| Age (years) | male (U/L) | female (U/L) |
|---|---|---|
| 20-29 | 65.9-670.2 (160) | 44-268 (87) |
| 30-39 | 70-533.6 (157) | 41-257.5 (83) |
| 40-49 | 67.8-549.6 (147.3) | 38-225.7 (82) |
| 50-59 | 64-452.1 (146) | 40-251 (89) |
| 60-69 | 50-355 (125) | 41.4-234.5 (86) |
| 70+ | 41-321.8 (104) | 38-200 (73.9) |
By race and ethnicity
| Race/ethnicity | male (U/L) | female (U/L) |
|---|---|---|
| Mexican American | 57-436.7 (156.8) | 39.5-189.4 (78) |
| Other Hispanic | 65.1-607 (161.6) | 44-276.5 (87.6) |
| Non-Hispanic White | 52-411 (131) | 38-212.7 (78) |
| Non-Hispanic Black | 91.7-808.1 (235) | 56.8-368 (125) |
| Non-Hispanic Asian | 65-501 (145.7) | 47.1-212.5 (86) |
Frequently Asked Questions
Why does CK vary so much between people?
CK enters the blood from skeletal muscle, and recent physical activity can raise it for days afterward. NHANES did not record recent exercise at the blood draw, so these distributions include that variation, which widens the upper tail.
Why is CK higher in males?
Males have more skeletal muscle on average, and CK levels track muscle mass. In these NHANES data, the male median is higher than the female median in every age group.
Why are there separate pages by race and ethnicity?
CK differs markedly across NHANES race and Hispanic origin groups, so these groups are shown separately. The groups are NHANES categories based on self-reported race and Hispanic origin. These pages pool all adults aged 20 and older and are not age-standardized, so part of any difference between groups reflects differences in age composition. The site reports the observed distributions and makes no claim about their causes.