10th July 2026

Assessing renal function

GFR is the most widely used proxy for renal function when prescribing medications. Serum creatinine levels are used as a surrogate for renal function, though this is affected by creatinine production as well as GFR. The GFR can therefore be overestimated in those with low body mass and the elderly population. 

The most used formula for estimated GFR (eGFR) is the Modification of Diet in Renal Disease (MDRD), which uses age, gender, and serum creatinine levels. However, there are several limitations:

• eGFR is unreliable at extremes of bodyweight, leading to underdosing of large patients and overdosing of small patients.
• eGFR is not authorised to be used in children or pregnant women.
• reductions in eGFR due to a rise in serum creatinine can lag behind the actual deterioration of GFR in acute kidney injury.