Normal GFR values vary with age. Newborns typically have a lower GFR, which gradually increases as they grow. For instance, a full-term infant may have a GFR of around 20-40 mL/min/1.73m², which increases to adult levels of about 90-120 mL/min/1.73m² by the age of two. It's essential to interpret GFR values in the context of age-specific norms.