Hi Dawnybee - sorry to hear your blood test result have given you a shock - it's good that you're spotting it early. Your GP sounds on the ball and that's really good. I don't know much about eGFR rates because mine has been fairly stable over the past 6 months since I started having regular blood tests. I've just had a look and mine does wobble about some months. I've looked online and this looked like a good link -
Love your kidneys - it's got good advice about lifestyle changes to diet etc. Especially important to drink plenty and avoid salt, (Also stop smoking and too much alcohol, but with RA you no doubt already have that sorted

!)
I think your GP may have said an
ACR urine test - this is a simple explanation that I found helpful. It sounds like it's a fairly routine test and presumably your GP will discuss treatment plans when the results come back.
Let us know how you get on, because I'm on the same MTX and folic acid as you, and it's always useful to know what sort of things to look out for.
Hope you're not too anxious - Sylvia xx
Be kinder than is necessary because everyone you meet is fighting some kind of battle