Several people have reported creatine related headaches before in this forum and elsewhere.

Yes, there may be a direct correlation between Creatine use and headaches due to taking high doses of creatine and not consuming enough fluids throughout the day.

The more creatine that is stored in the muscles, the more water is drawn into and stored in the muscles. Your body's need for water increases, as does your chance of becoming dehydrated. The onset of a headache is a common symptom of dehydration.

Maintaining hydration throughout the day can help prevent the development of headaches due to creatine use. You should drink water frequently throughout the day. Thirst alone is an inadequate indicator of dehydration. Caffeine is a diuretic that aggravates dehydration, so you should avoid consuming caffeinated products if you take creatine and suffer from headaches. Taking high doses of creatine can also be a factor in dehydration, so be sure to take only recommended doses.