egfr and creatinine 3 weeks apart

[iron lifter]

I had two diff docs pull labs for their own reasons, and i noticed a difference between these values.

3 weeks ago

egfr was 81
creatinine 1.0

today it was
egfr 72
creatinine 1.11

so i am like how can this be, i always take 2 days off training and no red meat/creatine so why would they change. i only did one thing differently i drank 1.5 liters of water
this time 1.5 hours before the draw. it looks like according to the link below - acute water intake lowers egfr values, interesting.

https://jasn.asnjournals.org/content/19/6/1041

Water ingestion can acutely affect GFR, although not necessarily in the direction one might expect. Using 12 young, healthy individuals as their own controls, Anastasio et al.8 found increased water intake actually decreases GFR. It might therefore seem that any “toxin” removed purely by glomerular filtration is cleared less efficiently in the setting of increased water intake; however, it is not certain such changes in GFR persist over time. Indeed, GFR was unchanged during a 6-mo randomized trial of increased water intake in older men who had benign prostatic hypertrophy.9 Of course, the populations in the two studies are different, and the main goal of the randomized trial was to evaluate bladder function rather than kidney function; as an aside, the study did show some improvement in bladder function, although the clinical significance of the findings is unclear.10

 

[whacked]

Well that’s interesting for sure. I would have definitely guessed the more hydrated the better.

 

[Type-IIx]

Dehydration negatively impacts kidney function (and therefore, eGFR). If the second test was euhydrated (i.e., your normal and also healthy level of water intake) it might actually be more reflective of actual kidney function. The take-home point is really to stay hydrated... some people do end up with kidney problems, chronic and acute, due to dehydration. If you're training hard, make sure you're getting plenty of sodium/salt/electrolytes and staying hydrated.

 

[qbkilla]

As far as I know it looks like a normal number in range nothing to worry about. I wouldn't expect it to be exactly the same. Your Blood pressure isn't going to be exactly the same every time it is taken, im surprised it is as close as it was the first time.

I wish they would stop giving EGFR like its a separate reading. Your EGFT is just your creatinine plugged into a formula, the only number that matters is the creatinine ignore the EGFR.

 

[iron lifter]

the first test was mid day after several meals and water, the second test was when i was fasted before the test. but I just read this only happens when you are fasted and than hydrate before blood work.

https://pubmed.ncbi.nlm.nih.gov/11473658/

Conclusions: In fasting adults, high hydration lowered GFR and increased natriuresis. After a meat meal, GFR increased only in the high hydration regimen and natriuresis only in the low hydration regimen. Hydration affects GFR and natriuresis under fasting conditions and after a meat meal.

 

[qbkilla]

But it's in range

If I get blood work 3 days in a row it might say 1.2, 1.1, 0.9.

If it jumped from 1 to 1.4 that might not be great, but it barley moved. Tomorrow it might be 1.2, 1.0, 1.11, 0.98 etc I wouldn't expect it to be exactly the same.

 

[Golden]

But it's in range

If I get blood work 3 days in a row it might say 1.2, 1.1, 0.9.

If it jumped from 1 to 1.4 that might not be great, but it barley moved. Tomorrow it might be 1.2, 1.0, 1.11, 0.98 etc I wouldn't expect it to be exactly the same.

This^

You’d assume there has to be natural fluctuations within the body as the systems are never static. Also there will be some room for manoeuvre with regards to lab testing, how long they had the sample before testing, etc.

 

[specter]

i have blood work done over several years and my EGFR goes from 110 and down to the lo 70's depending on alot of things, but as long as its above the limit im not worried.

 

[M@NU]

i had the same "issue" and was shocked by myself the last BW i did.
I made a topic called RBC and HCT where ive also asked this question.
creatinine june 0,9, august 1,1, septembre 1,0, octobre first BW 1,26 then 1,3
for me, my heart insufficiency medication changes those values quite heavily.
higher diuretics = higher creatinine
entresto = higher creatinine
...
so many factors affect creatinine imo.
from now on, i will probably switch to cystatin C since its way more accurate as far as i know

 

[Rudygreg]

I had two diff docs pull labs for their own reasons, and i noticed a difference between these values.

3 weeks ago

egfr was 81
creatinine 1.0

today it was
egfr 72
creatinine 1.11

so i am like how can this be, i always take 2 days off training and no red meat/creatine so why would they change. i only did one thing differently i drank 1.5 liters of water
this time 1.5 hours before the draw. it looks like according to the link below - acute water intake lowers egfr values, interesting.

https://jasn.asnjournals.org/content/19/6/1041

Water ingestion can acutely affect GFR, although not necessarily in the direction one might expect. Using 12 young, healthy individuals as their own controls, Anastasio et al.8 found increased water intake actually decreases GFR. It might therefore seem that any “toxin” removed purely by glomerular filtration is cleared less efficiently in the setting of increased water intake; however, it is not certain such changes in GFR persist over time. Indeed, GFR was unchanged during a 6-mo randomized trial of increased water intake in older men who had benign prostatic hypertrophy.9 Of course, the populations in the two studies are different, and the main goal of the randomized trial was to evaluate bladder function rather than kidney function; as an aside, the study did show some improvement in bladder function, although the clinical significance of the findings is unclear.10

The difference is miniscule, nothing to worry about. You were fasted, that's why. Don't get overly particular about subtle changes in lab reference values. Anything over 50-60 on gfr is normal.

 

[iron lifter]

thanks for the input guys appreciate. it

 

[MR. BMJ]

Yes, GFR will vary day to day for a host of different reasons. I would not worry about that.

 

[nicocujo]

Your numbers are good. I wouldn't worry about them.

 

[Killer.7]

Bumping this thread because I too have noticed my serum creatinine fluctuation quite heavily over time. Sometimes its lower sometimes its higher. This most recent blood work shows my creatinine at

128	67-117	umol/L
Glomerular Filtration Rate (eGFR)		63

This was after only 1 rest day off from the gym before doing these bloods.

I did bloods in June of this year and my creatinine was 120 and my egfr was 69

I really dont know how it could have went down other than not taking enough time off from the gym. Additionally Cystain C levels seem to be a much better indicator for us weight lifters when it comes to measuring kidney function. In 2019 I did tons of test and lots of 24 hour urine tests to determine what my real GFR was and it always came back better than normal.

Again the serum creatinine stuff really puzzles me.

 

[buck]

Numbers fluctuate. Water, samples being set to different labs can have different numbers etc. Unless they are far out of range there is usually no issue. Trends over time matter more i find.
And 10's of millions or errors are made by labs every year.

Results From Your Lab Test: How Accurate Are They? - GoodRx

Lab tests can be inaccurate more often than you think. The results depend on the type of test, where it is performed, the manufacturer, and how common the disease is.

www.goodrx.com

 

[tornquad201]

Definitely dehydration can effect this .

 

[Mountolympus]

I have try private lab and medical service , the difference was embarrassing. This because in this private lab using a method to evaluate egfr that it's not for bodybuilders

 

[Reno911]

I'd get a Cystatin C done.

 

[Flex500]

I had two diff docs pull labs for their own reasons, and i noticed a difference between these values.

3 weeks ago

egfr was 81
creatinine 1.0

today it was
egfr 72
creatinine 1.11

so i am like how can this be, i always take 2 days off training and no red meat/creatine so why would they change. i only did one thing differently i drank 1.5 liters of water
this time 1.5 hours before the draw. it looks like according to the link below - acute water intake lowers egfr values, interesting.

https://jasn.asnjournals.org/content/19/6/1041

Water ingestion can acutely affect GFR, although not necessarily in the direction one might expect. Using 12 young, healthy individuals as their own controls, Anastasio et al.8 found increased water intake actually decreases GFR. It might therefore seem that any “toxin” removed purely by glomerular filtration is cleared less efficiently in the setting of increased water intake; however, it is not certain such changes in GFR persist over time. Indeed, GFR was unchanged during a 6-mo randomized trial of increased water intake in older men who had benign prostatic hypertrophy.9 Of course, the populations in the two studies are different, and the main goal of the randomized trial was to evaluate bladder function rather than kidney function; as an aside, the study did show some improvement in bladder function, although the clinical significance of the findings is unclear.10

your creatinine fluctuating 0.11 over the course of 3 weeks is completely normal. You could get it tested in 3 weeks and maybe it would be 0.99 or maybe 1.21 and that could have your egfr move from like 91 to 60 with no actual change in kidney function.

There are tons of kidney threads on here and I've had my own lab scares. I've seen my creatinine at 1.67 only to follow up a week later with a 24 hour urine clearance to be normal, creatinine to be normal (literally a week later), and cystatin c totally normal.

As far as the study I think the point most make is that you do not want to be dehydrated when you give bloods. Most of us are also training hard and we tend to lean to a state of dehydration so it's important to ensure we are well hydrated but not to over hydrate when you are already adequately hydrated.

 

[Killer.7]

Did labs again, check this.

Creatinine		116	67-117	umol/L
Glomerular Filtration Rate (eGFR)		71