My fasting story is not related to a blood draw, but a knee surgery I had in 2010 (severely torn meniscus with a floater piece). My surgery was at 1:00 PM and they required me to fast after dinner, which I believe was around 6:30 PM, but the kicker was no fluids either because of the anesthesia. All I could do was brush my teeth and rinse whenever the dry mouth got unbearable.
Long story short, by the time they tried to find a vein during pre-op, I was so dehydrated that the nurse kept switching arms, even got frustrated over the struggle. After they were finally successful (took probably 5 - 6 times, but felt like 25) I asked why they made me stop fluids after dinner with my afternoon surgery time. The nurse said that they always require that! So I asked about if my surgery would have been at 8 :00 AM, would I still stop fluids right after dinner. They replied, Yes, of course, we want at least 12 hours without food and fluids to lessen the chance of vomiting due to the anesthesia.
No reasoning with the nurse after my surgery about the vast difference in morning and afternoon surgery start times leading to increased dehydration could be understood. You would think at the least the “Where Waldo” search for a usable vein would have caused an AHA! moment, but unfortunately, it never seemed to.
To this day I have never been so thirsty and miserable in my life. Now, years later, I never go anywhere (whether on work days or the weekend) without my large water bottle in tow, no matter the season or temperature!