Every couple of years, I have blood drawn and sent for fairly comprehensive testing through the Life Extension Foundation to which I subscribe. The price is a couple of hundreds bucks for complete chemistry, cbc, lipids, PSA, total and free testosterone, estradiol, C-reactive protein, homocystine, and glucose. My total testosterone was up a couple of hundred points to 777 on a lab interval of 241-827. Being 60 years old, I was quite pleased with this reading. I ascribe it to losing some belly fat, cutting refined carbs and sugar, the right kind of exercise and more sleep than I used to get in the former career. Lipids were 196 total cholesterol with HDL at 58 which is down a bit from the last time though the ratio still yields a < .5 risk level for CHD. One reading that was new was glomerular filtration rate, estimated. Rich, I am hoping you know how this estimate is made. My serum creatinine is 1.1 which is normal for me (I eat a lot of protein and lift fairly heavy weights) and, as I said, I am 60. The lab didn't have my weight. My estimate was <59 mL/min/1.73. the normal interval is 60-137. So, how is this "estimate" calculated is what I am wondering.