Are you talking about GFR or eGFR? For standard blood work the eGFR is an estimate -- that is what the "e" stands for. In looking through the literature, I found four different formulas for estimating GFR from standard blood work.
As I understand this, there are medical people in My Kidney who can correct me if I'm wrong, the GFR is a filtration rate for whatever that G thing is. The scale is 1 to 100. Thus, GFR is an estimate of the percentage of kidney function you have. During my last bloodwork, my eGFR was 57. One could say that my kidneys were functioning at 57% of a fully functioning kidney. What are we to make of this?
My nephrologist gave me a simple heuristic (buzzard meaning rule of thumb) to estimate "normal" GFR. For the average, healthy person, kidney functions remain at 100% until the age of 40. After that, the kidneys decline in capability about 1% per year.
I'll be 80 in a couple of weeks. That gives me 40 years of 1% decline or 40%. So, an eGFR for me of 60 (e.g. 100%-40%) would be normal. As mentioned, I'm at 57% and that is about normal given my age.
A nephrologist can run more sophisticated tests to better measure the actual GFR. So at what numbers should we start to worry?
My nephrologist told me that kidneys function well enough down to 10% before replacement is needed. So, I have another 37 years to go before worrying about a transplant.

he is right a GFR below 15 does not necessarily mean dialysis it depends on your symptoms but i agree a GFR in that range is scary i;m at a GFR of 50 still not happy so good luck to you

My doctor said as long as I stay above 20, I won’t need dialysis! Numbers matter but I think you need to take how you feel into consideration♥️

Mine said 10. But I will go by my symptoms.

No