Creatinine

Since creatinine production is relatively constant (based on muscle mass), rising blood levels signal declining kidney function. Elevated creatinine often occurs without symptoms until kidney function is significantly impaired. Early detection allows interventions to protect remaining kidney function through blood pressure control, diabetes management, and avoiding kidney-damaging medications.

Creatinine is part of standard kidney screening and most adults benefit from checking it once a year. If you have hypertension, diabetes, or take medication processed through the kidneys, your clinician may want it every three to six months. After starting a new nephrotoxic medication, 2 to 4 weeks is the typical recheck window.

At baseline / for screening: Once every 12 months from age 30 as part of a kidney panel. More frequently, every 3 to 6 months, if you have hypertension, type 2 diabetes, chronic kidney disease, or take medication processed through the kidneys.

When monitoring an intervention or change: Retest 2 to 4 weeks after starting a new medication that affects the kidneys (ACE inhibitor, ARB, SGLT2 inhibitor, diuretic, NSAID, certain antibiotics) to confirm stable function. After a meaningful change in blood pressure or diabetes control, retest at 3 months. Hydration on the morning of the draw can shift creatinine-based numbers, so reproduce conditions for reliable trend tracking.

Note: Creatinine reflects muscle mass and rises after intense resistance training. Wait 48 to 72 hours after heavy training before testing; after starting a nephrotoxic medication, retest at 2 to 4 weeks regardless of the routine cadence.