What is the estimated glomerular filtration rate (GFR) threshold for stage 1 kidney disease?

• A. 60-89
• B. 30-59
• C. 90 or higher
• D. <15

Answer: (C)

Stage 1 CKD is defined by a normal or near-normal filtering rate accompanied by evidence of kidney damage. The filtering rate threshold that marks stage 1 is a GFR of 90 or higher, typically expressed as ≥90 mL/min/1.73 m². The important point is that this stage isn’t diagnosed by the GFR alone; there must also be signs of kidney damage, such as albuminuria, structural abnormalities on imaging, or abnormal histology.

So, the threshold itself is 90 or higher, but stage 1 only applies when there’s additional evidence of kidney damage. If there’s kidney damage present with a GFR in the 60–89 range, that would be stage 2. Lower GFR ranges correspond to later stages (stage 3, stage 4, and stage 5) reflecting progressively reduced kidney function.