Hello,
Generally, a gastrointestinal illness manifests itself by liquid diarrhea, abdominal cramps, nausea and vomiting. It is also possible to have a slight fever or muscle pain. It should get better in a few days and take a week to resolve. If it doesn't, or if the symptoms get worse, it is recommended that you see a doctor.
To answer your question, in case of gastro, it is possible to feel dizzy, especially if hydration is not sufficient. Indeed, in the presence of vomiting or diarrhea, it is important to replace this fluid loss and drink an electrolyte-based solution, such as Pedialyte or Hydralyte.
Hopefully this answers your question,
Samantha Hui, pharmacy student
Under the supervision of Alexandre Chagnon, pharmacist