Creatinine flagged high on my panel again, is it the gear, the creatine, or just being a big lifter?

Got my metabolic panel back and creatinine is flagged over range again, second time now, and the eGFR came out low alongside it. Im sitting around 240lb, lift heavy 5 days a week, been on creatine for years and eat a ton of protein daily. Doctor took one look and started talking about kidney function which put the wind up me a bit. Is this actually my kidneys packing in or is it just the muscle mass and the creatine throwing the number off? Anyone else big get flagged for this and how did you actually work out whether it was real or not?

Creatinine is a breakdown product of muscle, so big lifters run higher than the lab range which is built around average blokes. One reading over range with everything else clean is usually just your mass, not failing kidneys. Two things skew it further, creatine supps and being dehydrated on the day, so drop the creatine a week or two before bloods and turn up well hydrated. If you actually want to know your kidney function get a cystatin C done, it doesn't depend on muscle mass so it cuts through the noise the creatinine adds. The real red flags are protein or blood in the urine and a creatinine that keeps climbing run after run, not one number slightly over.

Good points already in here. The one thing I'd add is to check your own baseline rather than the lab range, a muscular bloke with creatinine just over range and everything else clean is almost always fine. If you genuinely want certainty on the kidneys, a cystatin C plus a urine albumin test settles it, since neither is thrown off by muscle mass.

That flag is one nearly every big lifter sees at some point. Creatinine is a muscle breakdown product so the lab range, which is built around average sized people, reads you high just for carrying more muscle. If youre on creatine and eating high protein that pushes it up further, and being even a bit dehydrated on the day inflates it more. eGFR is only an estimate calculated off that same creatinine, so it looks artificially low when your creatinine is muscle inflated. Before you panic get a cystatin C, it doesnt depend on muscle mass, plus a urine albumin test. The real kidney red flags are protein or blood in the urine and rising blood pressure, not one number sat just over range with everything else clean.

Creatinine is a breakdown product of muscle so big lifters basically always run over the lab range, it is built around average sized people. One reading high with everything else clean is almost always mass, not failing kidneys. Two things skew it further, creatine supps and a high protein diet, so drop the creatine for a week or two before bloods and make sure you are properly hydrated on the day. If you actually want to know your kidney function get a cystatin C, it does not lean on muscle mass the way creatinine and the eGFR estimate do. The real red flags are protein or blood in the urine and blood pressure creeping up, watch those far more than one number sitting just over range.

Muscle mass throws creatinine every time, the lab range is not built for lifters our size. Stay hydrated, drop the creatine before your next draw and look at the trend over a few runs, not one flagged number.

Before you panic get a cystatin C run, it doesnt care about muscle mass the way creatinine does so it gives you a far cleaner read on actual kidney function. eGFR is just calculated off creatinine, so if your creatinine is muscle inflated the eGFR reads low even when the kidneys are fine. Stop the creatine for a couple weeks and hydrate properly the day before your draw, and ask for a urine albumin while youre at it. One number just over range with everything else clean on a big lifter is almost always nothing.

Creatinine reads high in muscular guys because it is a muscle breakdown product and the lab range is built around average people, so one reading slightly over with everything else clean is almost always mass not failing kidneys. Two things skew it further, creatine supps and a high protein diet both push it up, so drop the creatine for a week or two before bloods and make sure you are properly hydrated on the day. Your eGFR looks low because it is just calculated off creatinine, so if that is muscle inflated the eGFR reads artificially low, ask for a cystatin C test which does not depend on muscle mass if you actually want to know. The real red flags are protein or blood in the urine and a creatinine that keeps climbing run after run, not one number just over range.

Worth adding, if that number is bothering you get a cystatin C run alongside it. Creatinine is muscle dependent so a big lifter reads high off that alone, and eGFR calculated from it then looks artificially low. One creatinine slightly over range with urine and blood pressure clean is very rarely the kidneys.

Single high creatinine with everything else clean is almost always muscle mass, the lab range is built around average people not guys carrying serious muscle. Stop creatine for a week or two before your next panel and make sure you're hydrated, both skew the number up on their own. If you want the real picture ask for a cystatin C and a urine albumin, cystatin C doesn't depend on muscle mass so it won't get thrown off the way eGFR does.