Health note: This page is general education, not diagnosis or treatment advice. Do not change medicines, supplements, fluid targets, or a prescribed diet based on this page alone.
The numerical difference is straightforward: stage 3a corresponds to eGFR 45–59, while stage 3b corresponds to 30–44. The clinical picture is more nuanced than that dividing line.
Why the split exists
Lower eGFR generally corresponds to greater loss of kidney filtering function, but risk assessment also uses other information. A result near a boundary should not be interpreted in isolation.
Useful next steps
Learn how eGFR is estimated, review the broader CKD stages, and prepare questions for your healthcare appointment.