Told docs i drink 3-5l/day b/c on topamax (topiramate) but they insisted i was dehydrated. i'd had about 1.5l that morning. is it really possible i was dehydrated?

Dehydration: In view of your fluid intake I doubt you were truly dehydrated unless you were losing vast amounts of fluids through sweating, vomiting, diarrhea or failure of kidney function. A simple indication of dehydration is a significant drop off of urination as the body mechanisms try to preserve the body's tissue and vascular fluid volume. Certain Blood chemistries tell you your body fluid status