What cause dizziness like you want to pass out?

Usually cardiac: Usually either a drop in blood pressure or irregular/ too fast heart beat. Not enough blood flow to the brain = not enough oxygen to the brain = uh oh i don't feel so good and i feel like i could pass out.

Low BP: Loss of consciousness is due to low blood flow to the brain. Usually as a result of decreased blood volume (blood loss or dehydration) or expansion of the blood vessels ( spinal shock, sepsis, etc) or failure of the pump ( decreased heart output - rate or contraction problem). Often it is a combination problem.