McMahon Score (Rhabdomyolysis Risk)
McMahon Score for rhabdomyolysis (McMahon 2013): predicts in-hospital death or AKI needing renal replacement from admission values.
Open the calculator → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- Age
- 60 years
- Sex
- Female
- Initial creatinine
- 2.5 mg/dL
- Initial calcium
- 7.0 mg/dL
- Initial CPK / creatine kinase
- 50000 U/L
- Cause: benign (seizures/syncope/exercise/statins/myositis) or other
- Other cause
- Initial phosphate
- 5.0 mg/dL
- Initial bicarbonate
- 18 mEq/L
Result: McMahon 16/19 — very high risk.
The tool opens with these values already filled in. Replace them with your own.
What the result means
- < 6
- Low risk of death or renal replacement.
- Two cut-offs
- The derivation cut at 5 (below 5: about 3% risk, negative predictive value 97%). Later validation and a trauma consensus statement settled on 6 or more, which is what this uses.
- >= 6
- high risk; consider renal-protective therapy regardless of the CPK. Scores > 10 carry substantially higher risk.
What you enter
- Age (years)
- Sex (female adds 1 point)
- Initial creatinine (mg/dL)
- Initial calcium (mg/dL; < 7.5 adds 2)
- Initial CPK / creatine kinase (U/L; > 40,000 adds 2)
- Cause: benign (seizures/syncope/exercise/statins/myositis) or other (adds 3)
- Initial phosphate (mg/dL)
- Initial bicarbonate (mEq/L; < 19 adds 2)
How this is calculated
- Points
- age (1.5/2.5/3) + female (1) + creatinine (1.5/3) + calcium <7.5 (2) + CPK >40,000 (2) + non-benign cause (3) + phosphate (1.5/3) + bicarbonate <19 (2) = 0-19.
McMahon GM, Zeng X, Waikar SS. A risk prediction score for kidney failure or mortality in rhabdomyolysis. JAMA Intern Med. 2013;173(19):1821-1828. Read the source ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.