Hello, I am hypothyroid and have B12 deficiency that I have regular jabs for. I have been trying to get fitter and bought a Fitbit. I have started to notice that my resting heartrate is around 47, but when I exercise (run mainly) it ends up around 170-180. Doing little things like up and down stairs can leave me really out of puff but running I can do! I'm not really fit by any standards so can hardly be referred to as an athlete! Should I be concerned about such a low resting heartrate?