I just did a really intense aerobics class and now i have a headache. This is probably the most intense that i have ever worked out in recent times. (years).

I seriously doubt it's from dehydration because i drink a TON of water before/during/after workout and all through the course of the day.

My face was REALLY red after the class and stayed red a little longer. (which isn't totally normal for me... for it to be red a longer period of time after working out)

Did i just overexert myself? Any ideas?

I've had that happen when I've worked out at a high intensity and not eaten enough. Did you eat anything before your workout?

I keep a nutrition bar in my gym bag, and once or twice I've even taken a break during my workout to fuel when I've started feeling "off". I'd rather have to pause for a bit than end up with a splitting headache that takes hours to subside!

I had two slices of peanut butter toast and a banana before! Maybe it was just too long before... about 3 hours.

Hi
hope this helps, some other things besides hydration may cause a headache - a couple are to be sure to warm up and cool down and eat something sweet about a half hour before you start- like an orange or a tablespoon of peanut butter also help.
One other safety measure is to check with your doctor.

I have a doc appointment this coming Thursday to talk about blood sugar issues, so i will be sure to bring this up as well! Thanks for the input!

Have you checked your blood pressure? Red face, headache? That means high blood pressure to me. I wouldn't exercise again until I had my pressure checked first.

I get headaches after swim workouts if I'm not cautious about warming up & cooling down properly but it is due to the super controlled breathing involved. Is it possible you were not breathing enough?

Might it be caused by low electrolites (spelling :S)? I only tend to get a headache after i've been sweating loads and gone bright red when riding and i come away with a headache. Also drinking water won't replace them unless its that sports water stuff that has them added and drinking only water will only dilute them further. Perhaps talk to the aerobics instructor?