eGFR (Kidney)

eGFR (estimated glomerular filtration rate) estimates how well your kidneys filter blood, calculated from your creatinine, age, and sex — it's the number that actually reflects kidney function, not creatinine alone.

Reference range

Watch points

Critical: at or below 30 mL/min
High: at or below 60 mL/min

Same thresholds apply to men and women in this table.

Why hard-training athletes watch it

Because creatinine runs naturally higher in muscular athletes, an eGFR calculated from the standard formula can underestimate true kidney function in lifters — a known limitation worth raising directly with your clinician.

When to retest

Retest alongside creatinine and, if your clinician recommends it, a cystatin-C-based eGFR calculation, which is less affected by muscle mass.

Talk to your clinician

Stay well hydrated and discuss kidney function with your clinician. If your eGFR reads low but you're a lean, muscular athlete with no other kidney symptoms, ask your clinician specifically about the muscle-mass limitation of the creatinine-based formula.