My latest blood results showed: Serum creatinine level 47 umol/L [49.0 - 90.0]
Below low reference limit so what does this mean? I have been having lower back ache for some time?
Creatinine levels depend on body size and diet just before the test. Typically, if you eat more protein before the test you will get a higher number and larger people have higher values then smaller people. Strenuous exercise just before the test can also raise creatine levels. Thus you can get good deal of variance between tests. A low creatine level like yours is usually not a problem unless it persists.
I’m pretty sure it has nothing to do with your back.