When GFR is over 60

Your GFR is a measure of how well your kidneys are filtering waste from
your blood, and it can be estimated from a routine measurement of creatinine
in your blood.
Creatinine is a waste product formed by the normal breakdown of muscle cells. Healthy kidneys take creatinine out of the blood and put it into the urine to leave the body. When kidneys are not working well, creatinine builds up in the blood.
As people age, GFRs drop. However, a low GFR with a value below 60 suggests that significant kidney damage has occurred. This means that your kidneys are not working at full strength.

It is extremely important for you, especially if you are at high risk, to see your doctor or other healthcare provider once a year and ask about your GFR. Your doctor will use your GFR as a clue toward determining how well your kidneys are working. Other factors include protein (albumin) in your urine and the possibility that you may have diabetes or high blood pressure.

When GFR is over 60

GFR over 90mls/min/1.73m2 is normal unless there is other evidence of kidney disease, in which case CKD is stage 1. Other evidence of kidney disease may include:

Proteinuria or haematuria

A genetic diagnosis of kidney disease (e.g. known to be have a disease such as polycystic kidney disease)
Evidence of structurally abnormal kidneys (e.g. reflux nephropathy, renal dysgenesis).
If any of these are present, CKD stage is 1.
If GFR is 60-90 mls/min/1.73m2, the definition of CKD also requires one of the above features to be present, in which case CKD stage is 2. Because eGFR estimation is not very accurate at near-normal levels of kidney function, many labs only report eGFR >60, in which case it is not possible to tell apart stages 1 and 2 CKD. This doesn't matter as the things to do are just the same for stages 1 and 2. More about Stages 1 and 2 CKD.
Where any CKD stage classification is based on eGFR (estimated GFR):
Remember that eGFR is an estimate
Was race included in the estimation? (if not, add 21% if black)
About CKD stagesGFR>60
Stages 1+2 CKDGFR 30-59
Stage 3 CKDGFR<30
Stages 4+5 CKD

Patient information

Normal kidney function is a GFR of about 100, but eGFR results may only be shown as >60 or >90 (more than 60 or more than 90). Other abnormalities such as having blood or protein in the urine on testing may lead to a diagnosis of CKD despite normal or nearly-normal GFR.
Normal kidney function - EdREN
See foot of the CKD eGuide home page for more info links about CKD

See more in http://www.kidneyhospitalchina.org/gfr/