Hello,
Resting heart rate should be between 60-100 bpm; numbers much lower than 60 can be caused by a couple of things. One, people that are very cardiovascularly fit have lower resting heart rates. People that have longstanding heart disease, can also have lower resting heart rates. Drugs, like digoxen and metoprolol, can also slow your heart.
While your heart rate is not terribly slow, if you are not a fit athlete, you should discuss with your physician your concerns regarding your heart rate.
To your health,
Neil MD