The only people who should EVER look at creatinine for kidney health are people with very little muscle mass. I can do nothing and still read a 1.5, because I have a FFMI of over 30. Even if I had the best kidney function in the world it wouldn't be able to filter all the creatinine my muscles produce from NEAT alone.
Same here, 1.5 is my norm. I have blood work that dates back decades and the lowest I have been was 1.35 and as high as 1.6
About 10-15 years ago my GP said he wanted to me to see a nephrologist just in case. Three visits, two different 24 hr urine test that came back around the 1.5 mark with a conclusion that I'm fine.
My first conversation with the nephrologist was, "Why is the range for women lower than men?" (Knowing the answer) He said because men have more muscle mass and creatinine is a by-product of muscle metabolism. "Well if I'm carrying a fair amount more muscle than the average guy, wouldn't you expect it to be higher? His reply was, probably.
I do think you should always have it checked and pay attention to your creatinine levels. It's not so much the number itself but the tracking of the number if it starts to slowly increase. If you're seeing an increase, it's time for a better look.