Reference intervals for markers of renal function are critical in determining the point estimates for renal disease intervention before and during disease management. Estimates of glomerular function are becoming more practical than the traditional methods beset by insensitivity and high mean errors during estimation. Current tests for renal function tests diagnose renal insufficiency when less than a third of the nephrons are remaining in the both kidneys. Serum cystatin C and derived serum cystatin based estimated glomerular filtration rate are critical as a comparative determinant of values to distinguish diseased from health individuals being important markers for renal function which need to be diagnosed before the renal mass has been irreversibly diminished. However, reference intervals for the protein are not yet established amongst black in Southern Africa and it is necessary to determine these as it appears their usage in renal function estimation is becoming a viable alternative to traditional renal function markers.