There are many symptoms that should be cause for concern and lead to prompt medical evaluation, including:
A body temperature of 103 degrees Fahrenheit or higher
Skin that is hot, red, dry or particularly damp
Headache
Dizziness
Nausea and vomiting
Confusion
Loss of consciousness
Severe muscle cramping
Even if these symptoms are mild but last more than an hour, you should call your doctor or seek medical care.