gastroenteritis
"500mg (1 dose each day). 

When I took Doxycycline the first time, there was irritation along the back of my throat, followed by a slight headache.

The next day, I took my next dose and immediately my head felt tight and full of pressure. It took 9 hours to subside and almost double that to get rid of it completely. I looked up the side-effects on this site and apparently intra-cranial pressure is rare but can happen. This antibiotic may work wonders for some people but for me it was not a good experience.

I am now on a different antibiotic for my condition which is making me feel tired and hungry all the time. It's still better than crippling headaches.

Avoid Doxycycline if you feel ill with it. It's not worth the pain."