As you gain altitude, your red blood cells can't hold as much oxygen, which means once you start getting into the thousands of feet above sea level, you may get easily winded, have a headache, and feel nauseated. Go really high—like, say, 20,000 feet and up—and your head might feel like it's going to implode, you might puke, your lungs might fill with fluid, and you might die. Eight-time Everest summiter Dave Hahn and expedition doctor Deirdre Galbraith share some pointers on going up the right way.
(1) TAKE YOUR TIME: Nothing is proven by initial displays of physical prowess; walk at a pace that allows conversation and comfortable breathing. Your sleeping altitude shouldn't increase by more than about 1,000 feet a day; plan on active rest (like light exercise around camp) every third day.
(2) DRINK UP: It's crucial to take in plenty of fluid when the air is dry and your lungs are working overtime. Drink three liters a day; you should be peeing pale and frequently.
(3) CHOW DOWN: Appetite tends to decrease at altitude, but you've got to eat regularly to maintain strength, endurance, and warmth. A high-carb diet of 4,000 to 6,000 calories a day works best.
(4) PAY ATTENTION: If you develop symptoms of altitude sickness, take a rest day to allow your body to acclimatize. If you experience extreme symptoms, head to a lower elevation immediately.
(5) PARTY NON: Booze up top is a bad idea. It will hurt acclimatization and increase your risk of dehydration.
(6) JUST SAY MAYBE TO DRUGS: There isn't yet some magical cure for altitude sickness, but Diamox can be used responsibly and effectively. For instance, 125 mg at night before you sleep can help ease breathing and allow for more rest.