Had episode of lightheadedness 6 days ago while standing and talking. Had to put head between legs and sit. Got up to walk home and had to sit 3 x to get home -next door. I then laid down and put legs up and felt better but shakey. Husband took me to Dr....they kept me overnight checking cardiac enzymes...didn t check cbc,thyroid,b.s. etc. but they did do normal ekg, chest x-rays and postural blood pressures... they decided I was dehydrated as they had trouble getting in I.V. and tried 6 times... Still having episodes of extreme dizziness, seems worse in mornings and better toward evenings... I take vitamin b, vitamin c and nothing else daily. I am 43, healthy, exercise 3xweekly and do not sit all day. The day this occured I had worked out, and just went for walk around block at 10pm and was just standing talking... What could I have wrong ?