What is perscribed per the doctor fallowed pharmicopia and very effective, is 500mg 2x a day.
I have no doubt that 1000 mg/day is "very effective". Necessary for avoiding AMS at altitude is another matter altogether. Acetazolamide is a drug with very noticeable side effects, and the prescribed dosage is typically based on use with glaucoma patients. Most people who get a scrip simply to go above 12K' without incident find a nice balance with 62.5 or 125 mg twice a day: AMS is generally avoided without peeing every 20 minutes or feeling like your extremities are buzzing like a live wire (or having that celebratory beer taste like crap). These side effects can occur even at low dosage, but 500 mg at a shot is almost guaranteed to make your hike miserable without providing any additional protection from altitude sickness.
Bob Pickering's advice is sound: the best dose of any drug is the lowest at which it is effective. Your mileage may vary, but for the purpose of going high taking 1000 mg per day is serious overkill for most people.
