What are some causes of off and on weakness?

I sometimes get really weak either just sitting there at work, or when walking around the city. At other times, I feel fine doing the same activities.





I consider myself reasonably in shape. I run, walk, do martial arts, and am fairly active. But, some days-- or even parts of a day-- I get really weak for a while. It goes away after resting for a while.





Any suggestions for building stamina? Anyone experienced this?

What are some causes of off and on weakness?
It doesn't seem like stamina is oyur problem. The most likely reason you get this way is that your bloodsugar levels are too low. Next time you feel like that, try drinking orange juice or eating a popsicle or sugary candy. Turkey can also help with weakness as it a very good source of protein. If the problem does not go away, you start to develop headaches or muscle aches, see a doctor.
Reply:Low blood sugar is the reason that it happens to me. I usually ride it out. After a long rest, I go back to before I got weak.