McMahon Score
| Variable | Score |
| Age, years | |
| >50 to ≤70 | 1.5 |
| >70 to ≤80 | 2.5 |
| >80 | 3 |
| Female | 1 |
| Initial creatinine, mg/dL | |
| 1.4–2.2 | 1.5 |
| >2.2 | 3 |
| Initial calcium <7.5 mg/dL | 2 |
| Initial CPK (Creatine Phosphokinase) >40 000 U/L | 2 |
| Origin not seizure, syncope, exercise, statins, or myositis | 3 |
| Initial phosphate, mg/dL | |
| 4.0–5.4 | 1.5 |
| >5.4 | 3 |
| Initial bicarbonate <19 mEq/L | 2 |