Serum creatinine and glomerular filtration rate (GFR) are currently used to measure kidney function in clinical practices. The baseline GFR does not reflect full kidney function as kidney does not work at its maximum capacity under normal conditions. GFR increases acutely after heavy protein load and the increase represents recruitment of reserve. This increase is called renal functional reserve (RFR). It has been shown that measured GFR in normal individuals of Indian ethnicity is lower than that in Western population. It is not known whether that is physiological or pathological. Plasma clearance of iohexol is the current gold standard for measurement of GFR. We have already established procedures for measurement of GFR by plasma clearance of iohexol. Assessment of RFR, using most accurate reference method to measure GFR such as plasma disappearance of iohexol, is important to ascertain significance of low normal GFR in Indian population. The proposed study aims to evaluate RFR of healthy Indian subjects after protein load using standard method of measurement of GFR i.e. using plasma iohexol clearance. We propose to measure the RFR in prospective living renal donors who are extensively worked up to assess normality of clinical status. Pre and Post protein loading GFR will be measured by multiple sample plasma clearance of iohexol. Iohexol will be analyzed by HPLC. We aim to analyse association of RFR with post kidney donation renal function at 6 months in living renal donors.