If you've properly acclimatized yourself to altitude, you are no longer feeling the dizziness, headache and loss of appetite that altitude sickness can bring. However, the physiological changes themselves continue: You're breathing more rapidly. Lower air pressure means that moisture is evaporating more quickly from your skin. Your kidneys are working harder, so you're urinating more frequently; also, your body is depleting your glucose stores faster than at sea level [source: Askew].
To avoid dehydration, you'll need to take in more fluids than normal. This doesn't mean you should load up your pack with soda and beer, however. In fact, you should avoid alcohol and caffeine altogether since they can be dehydrating. Symptoms of dehydration mimic symptoms of altitude sickness. If you start feeling lightheaded or headachy, increase your water intake and take a break before continuing to a higher elevation.
You'll also want to stick to a high-carbohydrate diet to refuel glucose stores. Gorp, a carb-loaded blend of nuts, seeds, dried fruit and chocolate) is a great snack to pack and can be found at most camping stores. Once you've decided what to munch on the mountain, it's time to select a camp site and get cooking. In the next section, we'll tell you how to keep your tent from blowing away.