I've done a couple of Yoga classes before and today was my first time experience Bikram - doing yoga in a really hot room (probably more than 100°F, or 40°C).
I made through it, even though I felt dizzy a few times during the hour. I grabbed my water, drank half of it and the dizziness went away. Well, not bad for a first timer. However, I started having some terrible headaches and nausea a few hours after the class. It might be because I was still dehydrated. I slept a few hours, drank a few bottles of water, and a few bottles of water mixed with electrolyte powder. After a few more hours, the headache started become lighter, phew.
Next time, I'll bring a huge water bottle, and drink plenty of water before, during and after the class. Dehydration, stay away from me.