I have started going to the gym, but twice now i have became dizzy, feeling sick, and if i stand up seeing all black, even if i don't excersice a lot?

? dehydration: Make sure you hydrate before, during and after you exercise. If this issue continues it needs to be evaluated by a doctor.

Vasovagal response: Not sure whether this is occurring after you're running, lifting weights, going from lying to sitting, or sitting to standing, but these are extreme symptoms that need to be addressed by your doctor, so you can be safe while exercising. Seeing all black means you're not getting blood circulating to your eyes or head possibly ; if you're lifting heavy weights this could potentially be a problem.