should I be concerned about kidneys?

Hi all!
My GP's office has an electronic chart that routinely lets me know when new test results are posted. I usually don't look at them now since I've been feeling better but out of curiosity i checked out the ones that came to me today. It said my GFR was 69. for the past year at least it has been in the 90s but in november it dropped to 80s then december/january 70's and now 60's. Does anyone know if this fluctuation is normal? When i look at the report's guidelines it says that above 90 is normal and I would fall in the mild kidney damage range. Could all my medications (remicade, 6MP) be causing problems? My doctor hasn't brought it up so I'm not sure if its an issue or not.

Thanks Scifigal! Ill see if it's mentioned at any of my follow ups.