eGFR

What it is

eGFR (estimated glomerular filtration rate) tries to answer 'how well are my kidneys filtering?' — but it isn't measured directly; it's calculated, most often with the 2021 CKD-EPI equation from your creatinine plus age and sex. Because creatinine depends on muscle mass, eGFR inherits that limitation: it can read lower in very muscular people and higher in those with less muscle, and it's least reliable at the extremes and around a single borderline result. Notably, the 2021 equation removed the race coefficient that older versions used, and eGFR is typically read alongside creatinine and a urine test for protein (urine albumin-to-creatinine ratio), with trends over time mattering more than any one value.

Typical range

Reference ranges vary between laboratories, and what is normal for you depends on your own history. Your own lab’s range is the one printed on your report.

Worth asking your clinician

• Which eGFR equation was used for my result, and how well does it fit someone with my build?
• Would a cystatin C-based estimate or a urine albumin test add useful context to my eGFR?
• Is my eGFR trending over time, or is this a single snapshot we should confirm with a repeat test?