Is there a particular rare kidney disorder that creatine is contraindicated for? Because kidney disease is not rare, something like 14% of US adults have kidney disease.

My lay person understanding is that supplemental creatine screws with a common lab test to screen for kidney problems. Let your physician know if you are taking any supplements so they can interpret your lab test results appropriately or order different tests.

https://www.kidney.org/kidney-topics/creatinine

I don't know the specifics beyond the fact that your kidneys play a key role in both synthesizing natural creatine and filtering out creatine from your body, and as thus is generally not recommended as a supplement if you have any sort of kidney disorder.

Creatine raises creatinine in kidney function tests. For a healthy person, this isn't a problem, but if you already have high creatinine (from a kidney problem), it makes it harder to interpret test results.