Creatine Kinase

Other marker

Creatine Kinase

Category: Other
Unit: U/L

Enzyme found predominantly in skeletal muscle, cardiac muscle, and brain. The most sensitive marker of skeletal muscle damage, used to diagnose rhabdomyolysis and myopathies.

PED Notes

Heavy resistance training routinely elevates CK to 500-2000 U/L within 24-72 hours. This is physiological, not pathological. AAS can potentiate exertional rhabdomyolysis — case reports document AAS-induced myopathy with extreme CK (>10,000 U/L). Trenbolone is particularly associated with higher muscle damage. Athletes on statins (prescribed for AAS-worsened lipids) face compounded CK elevation risk. Always draw CK after 48-72 hours of rest for a meaningful baseline.

Interpreting CK levels in athletes:

  • <500 U/L (resting): Normal for trained athletes
  • 500-2000 U/L (post-training): Expected after heavy resistance training
  • 2000-5000 U/L: Monitor hydration, reduce training volume, recheck in 48-72 hours
  • >5000 U/L: Rhabdomyolysis risk — medical evaluation and aggressive hydration required
  • >10,000 U/L: Emergency — high risk of acute kidney injury (AKI). Dark/cola-coloured urine is a red flag

Supplements:

  • CoQ10 (Ubiquinol) -- 200-300mg/day: Supports mitochondrial function, reduces exercise-induced CK. Critical if on statins (which deplete CoQ10)
  • Magnesium (Glycinate or Taurate) -- 400-600mg/day: Supports muscle relaxation, ATP production
  • Taurine -- 2-3g/day: Stabilises muscle cell membranes, may reduce exercise-induced damage
  • Omega-3 (EPA/DHA) -- 3-4g/day: Anti-inflammatory, may reduce muscle damage markers

Lifestyle:

  • Implement deload weeks every 4-6 weeks (reduce volume by 40-50%)
  • Avoid combining maximal eccentric training with new AAS cycles
  • Avoid NSAIDs during peak CK elevation (can worsen renal stress)
  • Never combine heavy training with alcohol (independent rhabdomyolysis risk factor)
  • Monitor kidney function (creatinine, eGFR) alongside CK if persistently elevated
  • If on statins: discuss with prescribing physician if CK is persistently >5x upper limit

References:

  • Mougios, V. (2007). Reference intervals for serum creatine kinase in athletes. British Journal of Sports Medicine, 41(10), 674-678. DOI: 10.1136/bjsm.2006.034041
  • Baird, M. F., Graham, S. M., Baker, J. S., & Bickerstaff, G. F. (2012). Creatine-kinase- and exercise-related muscle damage implications for muscle performance and recovery. Journal of Nutrition and Metabolism, 2012, 960363. DOI: 10.1155/2012/960363
  • Cervellin, G., Comelli, I., Benatti, M., et al. (2017). Non-traumatic rhabdomyolysis: background, laboratory features, and acute clinical management. Clinical Biochemistry, 50(12), 656-662. DOI: 10.1016/j.clinbiochem.2017.02.016

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Reference Ranges

Standard Range

30 - 200 U/L

VitalMetrics Range

80 - 500 U/L

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