Creatinine

Measured in mg/dL

A muscle waste product your kidneys filter out — useful for kidney function, but heavily influenced by how much muscle you carry.

What it is

Creatinine is a waste product made at a fairly steady rate as your muscles do their normal work; healthy kidneys filter it into urine, so the amount left in blood is used as a window into kidney filtering. Its biggest caveat is that it depends on muscle mass: someone very muscular can run higher without any kidney issue, while someone with less muscle mass may read deceptively low. It's read alongside BUN and eGFR (which is calculated from it), and it can also shift temporarily with intense exercise, a large meat meal, dehydration, or certain medications — so it's usually interpreted as a trend rather than a single snapshot.

Typical range

  • Male0.74–1.35 mg/dL
  • Female0.59–1.04 mg/dL

Source · Mayo Clinic (Creatinine test) (2026)

Reference ranges vary between laboratories, and what is normal for you depends on your own history. Your own lab’s range is the one printed on your report.

Worth asking your clinician

  • Given my muscle mass and activity level, how should my creatinine be interpreted?
  • Could my hydration, recent exercise, or anything I'm taking have affected this value?
  • Would tracking my creatinine over time, or looking at another kidney marker like cystatin C, add useful context?