It is usually related to either a viral infection or food poisoning. One of the major complications of gastroenteritis is dehydration. Dehydration means that there are not enough fluids in your system to maintain your blood pressure and urine output.
Dehydration can cause a worsening of symptoms and additional feelings of weakness and dizziness.
If you cannot tolerate oral fluids, or cannot keep up with the fluid loss, intravenous fluids are sometimes necessary. The earliest tolerated fluid is usually in the form of ice chips, a few at a time. Add clear liquids over your ice chips and sip constantly. Popsicles, broth, and jello are usually tolerable. Omit aspirin and Advil which are stomach irritants.