My temp. gauge climbs to HOT; not sure what to replace - Thermostat or Fan relay on 2002 Honda Civic Si

Driving along and my temperature gauge rises to hot. Sometimes it the temp. will drop on the gauge, some times it won't.

Asked by for the 2002 Honda Civic Si
3 answers
does the fan work? if fan works relay is good
I would try changing the t stat if that doesnt work then I would check the head gasket
Have you checked the coolant level (cold), in both rad. and reservoir?