More accurate test  is GFR (glomerular filtration rate). Normal GFR is 90-120 ml/my/1.73 meter surface area. In old age GFR may be less .there may be little variation in normal GFR in different laboratory. Creatine is metabolic products of nitogenous food, restriction of heavy exercise,restriction of heavy protein diet especially red meat helps in keeping creatine under control.take more fibres,, Upper level of normal creatinine is 1.4-1.5 in different laboratory