While it is nothing to sneeze at a lot of things can impact creatinine. Although I must say it's generally more stable than BUN. Here are a few things I'd say (I'm no experts like the others but have an advanced degree and sold diabetic supplies for years)....
1. Look at creatinine over the course of time. Ex: I have been 1.45-1.55 for 15 years. That is not as concerning as someone who has been 1.0 for 10 years and suddenly is at 1.75.
2. Are you taking medications? I take an ace inhibitor/diuretic combo for blood pressure and that will raise creatinine 10-20%.
3. How is the totality of your bloodwork and health? Meaning when we look at someone whose bloodwork is normal up and down the line I'm talking lipids, liver values, uranalysis (if you got that), blood pressure and all other blood markers it is likely there is not a major kidney issue. I guess what I mean is I've seen a shit load of patients in kidney failure and their bloodwork, even in early stages most of them have a lot of jacked up numbers.
4. Training, diet and hydration: This does have an affect on your readings although not to the extent many act like it does. I will say if I don't fast, eat an assload of meat, train very hard and don't drink enough while still taking my ace inhibitor/diuretic I can make my BUN go sky high and my creatinine go up another 10-15%. In the other hand we often act like waking a mile will be the reasoning our alt and ast are 150 and not the 150mgs of anadrol we just took
Not a bad idea to do a urinalysis or 24 hour urine screen.
I know how this goes hell when I was 20 yrs old a doc sent me to the ER and they were sending me to a person to get on the di or list as my creatinine was 1.58. Went to a kidney specialist and they are and were 100% healthy.
15 years later and I am still 1.45-1.55.