Understanding Kidney Markers: Creatinine vs Cystatin C

TropicStrength · Post by **TropicStrength** » Fri Jan 23, 2026 2:30 am

My creatinine is 1.4 mg/dL and my GFR is 65. The doctor is worried about Stage 2 Kidney Disease. I have 220lbs of lean mass. Should I be worried?

MedellinMuscle · Post by **MedellinMuscle** » Fri Jan 23, 2026 3:15 am

Creatinine is a byproduct of muscle mass. High muscle mass = high creatinine. Standard GFR equations fail for bodybuilders.

AndeanLifter · Post by **AndeanLifter** » Fri Jan 23, 2026 4:00 am

Run a Cystatin C test. It is independent of muscle mass and gives a much more accurate GFR for athletes.

LatinoBulk · Post by **LatinoBulk** » Fri Jan 23, 2026 4:50 am

I bet your Cystatin C GFR will be over 90. Most doctors don't understand this nuance.

CaliFlex · Post by **CaliFlex** » Fri Jan 23, 2026 5:40 am

Do you supplement with Creatine? That also bumps creatinine numbers.

TropicStrength · Post by **TropicStrength** » Fri Jan 23, 2026 6:25 am

Yes, 5g daily. I didn't stop it before the test.

MedellinMuscle · Post by **MedellinMuscle** » Fri Jan 23, 2026 7:10 am

There is your answer. Muscle mass + Creatine = False High Creatinine.

AndeanLifter · Post by **AndeanLifter** » Fri Jan 23, 2026 7:45 am

Check your Urea/BUN as well. High protein diets will always keep BUN near the top of the range.

LatinoBulk · Post by **LatinoBulk** » Fri Jan 23, 2026 8:25 am

Don't let them put you on meds until you get the Cystatin C result.

TropicStrength · Post by **TropicStrength** » Fri Jan 23, 2026 9:05 am

I'll order it privately. Thanks for saving me from a panic attack.