I am a 71 year old male. My serum creatinine recently rose to 1.4mg/dl (eGFR = 55.3ml/min) from 1.3mg/dl. My internist says that this means I am in stage 3 of chronic kidney disease (this is scary). He prescribed lisinopril, since my BP was 125/75 and he said it should be < 120 systolic. I am OK with that. My micro albumin test showed an albumin of 5mg/l and a urine creatinine of 175mg/dl, which is quite high. I am rather large, over 6 feet, exercise a lot, including weights, and I am more muscular than average. I have impaired fasting glucose, but my HbAIC is 5.5%. I was taught that muscular individuals have a higher serum creatinine, so I asked him if there is a more accurate way of determining GFR, and he said yes, but they didn’t do that anymore and just went by the serum creatinine. I went home and checked my medical records that I keep. At age 31, I had gross hematuria after a 3 mile run and got a complete renal workup for that. My creatinine then was 1.2mg/dl (eGFR at that age 80ml/min). Therefore they did a creatinine clearance test, with 24 hour urine which gave a GFR of 127ml/min. I suspect my GFR is now lower with age, but I doubt it is as low as 55. I don’t want to be my own doctor, but should I ask him to order a creatinine clearance test? A cystatin-C test? Should I see a nephrologist? I am very active and don't want to think about dialysis in my future. Sorry for the US units. I should have converted them for you. Thanks.