Hi Bea, The first thing is always to check the CO2 — it can change quickly. Our patients have a standing order and for a while, check electrolytes at least every 2 weeks (or if they feel like Diamox is not working as well as it used to). Only then, should you try to increase the dose to see if it is not as strong as you need. Please remember the evening dose is the most important, and needing 500mg at night is not unusual at all. Everything I know about making Diamox work (and keeping it working) is in the chapter on Diamox pearls in The Driscoll Theory. More advice is in some of the videos like this one: (cut and paste into your browser): http://prettyill.com/videos/watch/lets_talk_about_diamox_updated Good luck, my friend!