Blood results - fbun, creatinine, e gfr

[JimB]

Rip

Quick question. 40 year old male, 6’1 250 lbs with significant lifting history (565 squat, 450 bench, 610 deadlift). I continue to train hard and take creatine.

Recently got blood work with following results - any concern?

Fbun 26 mg/dl
Fcreatinine 1.64 mg/dl
De-gfr 54 ml/min

Thanks

Jim

[Mark Rippetoe]

What are the reference ranges for these values? Total testosterone levels?

[JimB]

Mark

Reference ranges included below. Also to note - among the tests run, no other out of range values.

FBUN 6-20 (mg/dL)
FCreatinine 0.67-
1.31 (mg/dL)
Fe-gfr >or=60 (mL/min
)

They didn’t run total test

[Mark Rippetoe]

Looks like your "doctor" thinks a guy like you with big muscle mass eating a lot of protein and taking creatine should have kidney problems, even if you don't. They have calculated a proxy GFR number based on a value that will be elevated due to your muscle mass and diet. Don't bother asking about the test. Maybe drink more water after you get up in the morning, and make sure that the next time they draw blood you're hydrated and 3 days past your last workout. Get a better doctor, and good luck with that.

[JimB]

Thank you. The better doctor one is definitely a challenge. Appreciate you taking the time to review this

[Jason Donaldson]

The question is, who ordered this blood work, why, and how are they reacting?

I've seen similar on my routine physical blood panels,...and my PCP didn't bat an eye, because of how the levels are consistent with protein intake, creatine supplementation, and heavy training. He's very happy I'm training...he's a DO, so I don't know if that helps. I've heard they're generally better locked on in multiple ways, but my n=1.

[Mark Rippetoe]

The majority of PCPs don't even know what GFR is, and can't actually pronounce the word. They have memorized some values, and that is all.

Influence of Muscle Mass and Physical Activity on Serum and Urinary Creatinine and Serum Cystatin C - PMC

Despite the important influence of muscle mass on serum creatinine, the different equations used to predict GFR do not include parameters of body composition such as lean mass.

[JimB]

Incredibly helpful, thank you.

May I ask - I’m in the wonderful city of New York. Would you happen to know of any doctors (virtual or otherwise) that might be better? Certainly if not appropriate to discuss here, just let me know. However, as you can imagine, it is very difficult to find someone good

[Railbob1776]

If you're concerned about the eGFR request a cystatin-c test. The cystatin-c test is a reliable kidney function test whereas the eGFR number is just the result of a formula that tries to give an indication on kidney function. I had a "low" eGFR once (under 60) and the cystatin-c test said I was fine and my last metabolic panel had my eGFR in the 80's. Silliness.

[dalan]

Exactly what Mark said. My eGFR has been mostly in the 60's for the 17 or 18 years I've been keeping track. It's gone as low as 54 and then the next time a few months later it was 68, probably due to the factors Mark mentioned - hydration and not training for a few days so that absolutely makes a difference. I've also had a urine test for protein in the urine and that was clean so between that and the fact that my eGFR has been consistent and not getting worse for going on two decades, I'm probably doing ok despite not having great "numbers" on blood work.