My serum creatinine result is 46 umol / l. what does it mean?

Normal, look at eGFR: It is just above 1.0mg/dL and is well within the normal range. You may wish to look at the estimated glomeular filtration rate (eGFR) which takes age, race and gender into account. If your eGFR is above 90 there is no cause for concern.

Creatinine: Creatinine ia a break -down product of creatinine phosphate from muscle and is used as a clinical marker for renal function due to its high filtration in the kidneys with little excretion. Decreased level could be explained by decreased muscle mass.