Aw mama, ang stress at lack ng tulog talaga ang nagpapalakas ng anxiety, more than the biscuit and water you had, honestly, kasi fasting labs naman usually pwede pa ng fluids (pero confirm with the lab to be sure!). A few of us who've done fasting labs agreed na ang key talaga is mag-hydrate well the day before, get some rest if you can even just for an hour or two, at eat a good dinner the night before, kaya good thing you had something light. For the dizziness worry, just let the lab staff know you're anxious and hadn't slept well; they deal with this all the time and can have you sit a bit after if needed. Honestly mama, I think it's the stress and sleeplessness talking more than anything else, pero if you're really worried about how you'll feel, maybe best to double-check with your doctor beforehand so you go in with peace of mind, kaya one less thing to worry about.