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Understanding Kidney Markers: Creatinine vs Cystatin C
Posted: Fri Jan 23, 2026 2:30 am
by TropicStrength
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?
Re: Understanding Kidney Markers: Creatinine vs Cystatin C
Posted: Fri Jan 23, 2026 3:15 am
by MedellinMuscle
Creatinine is a byproduct of muscle mass. High muscle mass = high creatinine. Standard GFR equations fail for bodybuilders.
Re: Understanding Kidney Markers: Creatinine vs Cystatin C
Posted: Fri Jan 23, 2026 4:00 am
by AndeanLifter
Run a Cystatin C test. It is independent of muscle mass and gives a much more accurate GFR for athletes.
Re: Understanding Kidney Markers: Creatinine vs Cystatin C
Posted: Fri Jan 23, 2026 4:50 am
by LatinoBulk
I bet your Cystatin C GFR will be over 90. Most doctors don't understand this nuance.
Re: Understanding Kidney Markers: Creatinine vs Cystatin C
Posted: Fri Jan 23, 2026 5:40 am
by CaliFlex
Do you supplement with Creatine? That also bumps creatinine numbers.
Re: Understanding Kidney Markers: Creatinine vs Cystatin C
Posted: Fri Jan 23, 2026 6:25 am
by TropicStrength
Yes, 5g daily. I didn't stop it before the test.
Re: Understanding Kidney Markers: Creatinine vs Cystatin C
Posted: Fri Jan 23, 2026 7:10 am
by MedellinMuscle
There is your answer. Muscle mass + Creatine = False High Creatinine.
Re: Understanding Kidney Markers: Creatinine vs Cystatin C
Posted: Fri Jan 23, 2026 7:45 am
by AndeanLifter
Check your Urea/BUN as well. High protein diets will always keep BUN near the top of the range.
Re: Understanding Kidney Markers: Creatinine vs Cystatin C
Posted: Fri Jan 23, 2026 8:25 am
by LatinoBulk
Don't let them put you on meds until you get the Cystatin C result.
Re: Understanding Kidney Markers: Creatinine vs Cystatin C
Posted: Fri Jan 23, 2026 9:05 am
by TropicStrength
I'll order it privately. Thanks for saving me from a panic attack.