eGFR (estimated glomerular filtration rate)

What it means

Labs calculate eGFR from your creatinine level, a waste product from muscle, along with factors such as age and sex. Some labs also use cystatin C, which is less affected by muscle size and diet.

MedlinePlus gives these general ranges, which your clinician interprets for you:

• 90 or above: probably normal kidney function
• 60 to 89: may be early kidney disease, especially with other signs of damage
• 15 to 59: may be kidney disease
• Below 15: may be kidney failure

Kidney disease is generally diagnosed when eGFR stays below 60 for 3 months or longer, or when there are other signs of damage such as protein in the urine. A single low result can come from dehydration, a hard workout or a high-protein meal.

Because creatinine comes from muscle, very muscular or very frail people can get misleading results, which is one reason cystatin C testing exists.

Why it matters

Your eGFR helps decide safe protein targets and how closely kidney function is watched during GLP-1 side effects.