My glomerular filtration rate has been very high for years, urea is very low, creatinine is always around the lower range. Is this a renal problem?
No. eGFR (estimated GFR) is a number calculated from your serum creatinine and it is affected by the filtering function of your kidneys as well as other factors such as muscle mass. Low GFR (and high serum creatinine or urea) is a likely sign of abnormal filtering function of the kidneys. However, low serum creatinine does not indicate renal disease.