Creatine kinase optimal range and reference range
Compiled by Alina Radu, founder of Sera, from the published sources below · Last reviewed November 9, 2026
Sera's bands for Creatine kinase, which differ for men and women:
- Female: Optimal 0 – 200 U/L (0 – 3.33 μkat/L); out of range below 0 or above 200 U/L.
- Male: Optimal 0 – 320 U/L (0 – 5.33 μkat/L); out of range below 0 or above 320 U/L.
Evidence grade: Published reference interval. A band that primarily reflects a published adult laboratory or population reference interval. It is not necessarily applicable to every assay or laboratory.
All units
| Unit | Applies to | Optimal | Sufficient | Out of range |
|---|---|---|---|---|
| U/L | Female | 0 – 200 | — | below 0 or above 200 |
| U/L | Male | 0 – 320 | — | below 0 or above 320 |
| μkat/L | Female | 0 – 3.33 | — | below 0 or above 3.33 |
| μkat/L | Male | 0 – 5.33 | — | below 0 or above 5.33 |
No separate Sufficient band is currently defined for this marker.
What the evidence says
The band ends at 200 U/L in women and 320 U/L in men, the adult interval an NHS laboratory prints, and within the upper limits a 2025 European systematic review found for people of European and Asian ancestry. Where the client's sex is not recorded, the men's figure is used. Laboratories disagree widely, from 170 U/L for men in a US reference table to about 400 U/L in the Nordic interval, so the laboratory's own range takes precedence. A raised CK usually means muscle damage. Hard or unaccustomed exercise in the previous days, a muscle injury, an intramuscular injection and statins all raise it, so ask about each before reading a high result. People of African ancestry run much higher without disease, with upper limits of 520 to 810 U/L in Black men. A low CK is not flagged: it mostly reflects low muscle mass and has no published threshold. 1 μkat/L equals 60 U/L.
Sources
- Creatine Kinase (CK) — Exeter Clinical Laboratory International, Royal Devon University Healthcare NHS Foundation Trust, 2019 · Laboratory / reference-interval sourceNHS laboratory adult interval for serum CK: men 40 to 320 U/L, women 25 to 200 U/L. The page adds that the range is broad and skewed to the top, that CK falls with age, and that Black men run highest. Revised March 2019.
- Kreatinkinas, P- — Karolinska Universitetslaboratoriet (Karolinska University Hospital, Stockholm), 2025 · Laboratory / reference-interval sourceSwedish adult interval in microkat/L, taken from the Nordic NORIP reference project: women 0.6 to 3.5, men 18 to 49 years 0.8 to 6.7, men 50 and over 0.7 to 4.7 (about 210, 400 and 280 U/L at the top). Revised August 2025. Confirms the μkat/L reporting unit and that the men's upper limit is higher.
- Creatine kinase (CK) — University Hospitals Birmingham NHS Foundation Trust, Pathology, 2026 · Laboratory / reference-interval sourceAdult interval on the Abbott assay: women 29 to 168 U/L, men 30 to 200 U/L. States that CK is higher in men and in Black populations, and that exercise, muscle trauma and statins raise it. Updated August 2026. A tighter upper limit than Sera's proposal, cited to show how far laboratories differ.
- ABIM Laboratory Test Reference Ranges, January 2026 — American Board of Internal Medicine, 2026 · Laboratory / reference-interval sourceUS reference table used for internal medicine certification: total CK women 30 to 135 U/L, men 55 to 170 U/L. The tightest of the intervals found, cited as the North American comparison.
- What Are the Normal Serum Creatine Kinase Values for Skeletal Muscle? A Worldwide Systematic Review — Aleksovska K, Kyriakides T, Angelini C, et al. (European neuromuscular authors) — European Journal of Neurology, 2025 · Peer-reviewed publicationSystematic review of CK reference studies: upper limits of 227 to 440 U/L in Caucasian and Asian men and 520 to 810 U/L in Black men, and 135 to 248 U/L in women (up to 354 in Black women). The proposed edges of 320 and 200 sit inside the non-Black ranges.
- Creatine kinase in the U.S. population: Impact of demographics, comorbidities, and body composition on the normal range — George MD, McGill NK, Baker JF — Medicine (Baltimore), 2016 · Peer-reviewed publicationNHANES analysis: the 97.5th percentile of CK was 382 U/L in white men and 1001 in Black men, 295 in white women and 487 in Black women. Supports the note that people of African ancestry run well above a standard upper limit.
- Creatine Kinase — MedlinePlus, US National Library of Medicine, 2023 · Government / public-health guidanceStates that a raised CK usually means muscle damage, from disease, injury, certain medicines such as statins, or recent intense exercise, and that normal levels depend on age, sex and race. Gives no numbers.
What CK (Creatine Kinase) measures
An enzyme that muscle cells release into the blood when they are worked hard or damaged.
Raised after strenuous or unaccustomed exercise for several days, and with muscle injury, some statins and hypothyroidism. It also runs higher in men and in people of African ancestry, so a mildly raised value in an active client is usually exercise, not disease.