eGFR fluctuation and the creatinine denominator problem

On the subject in the title: eGFR fluctuation and the creatinine denominator problem Working notes rather than a conclusion.

General question, not a request for advice about my own care — I know the difference and I would rather be told to see my prescriber than get an answer that pretends otherwise.

I have a panel in front of me with one value outside the reference interval and everything else within it. My instinct is that a single out-of-range result on a single draw is close to uninformative, and I would like to understand how the people who read these professionally think about that.

What I am actually asking is how to tell an interesting result from an uninteresting one before booking an appointment about it.

I read the opening post twice before replying, because I had assumed the opposite.

Time of day: some biomarkers vary across the day. Cortisol in the morning differs from cortisol in the evening. Comparing results from different times of day is comparing things that are not the same.

For anyone arriving from a search: the marked solution above is the direct answer, and the replies underneath it add the caveats that make it safe to use.