Elevated creatinine levels (in absence of supplementation) is a sign of kidney issues. There are many studies showing no reverse link i.e. supplementing creatine damaging kidneys

https://link.springer.com/content/pdf/10.1186/s12882-025-045...

Okay but logically kidney issues leading to high creatine does suggest that creatine is not all that good for the body, no? else why would the kidney keep it under control?

Would you suggest that white blood cells are "not all that good for the body" because they're amped up during a bout of sickness?

Maybe they aren't! But you can't infer that from the mere correlation. Hence that phrase about its relationship to causation.

No, elevated creatinine levels is only a sign of kidney disease if all else remains equal. Consuming more creatine will naturally increase production of creatinine because creatinine is a byproduct of the kidneys processing creatine.

In other words, it's not a very reliable signal for kidney disease. There is a more reliable blood test called a "Cystatin C" test.