How to Prevent Altitude Sickness When at High Altitudes

Some people have problems with altitude sickness when traveling at high altitude destinations in South America such as Cusco, Lake Titicaca, Uyuni Salt Flats and the altiplano areas in Chile and Argentina - and sometimes even when in Quito, which is at about 9,000 feet. Cusco is at about 11,000 feet and other areas mentioned can be up around 14,000. The best viewpoint at Rainbow Mountain, which is becoming more popular, is at about 17,000 feet. You can get up to 13,000 feet and higher on treks from Cusco.

I've never had a problem in Cusco, but my wife did. I did have a headache at Lake Titicaca though after too much walking on my arrival day. Luckily my guide gave me a pill that helped.

Rapid ascent to heights exceeding about 8,000 above sea level can cause oxygen saturation of hemoglobin in the body to decrease.  Breathing and heart rate increase immediately, and the heart beats faster. For most people, that's the worst of it since their bodies adapt and the concentration of red blood cells increase. For others, that feeling of breathlessness soon leads to a pounding headache, nausea and vertigo.

What can you do to try to prevent this, or at least make it more tolerable?

• Consult with your physician before your trip to see whether you should come prepared with a prescription of acetazolamide (Diamox). Taking doses of 125 mg twice daily, starting a full day before you travel to high altitude, will help you to metabolize the thinner air. Acetazolamide is also available over the counter in Peru for pretty cheap. (Be sure to choose one of Peru’s major chain pharmacies — Inkafarma, Pharmax, Boticas Arcangel, etc. to make sure you get the real thing. But acetazolamide is not for everyone, including those allergic to sulfa drugs — another reason to first consult your doctor.
• Consider Sorojchi High Altitude Pills, a Bolivian-made, over-the-counter remedy, containing 325 mg of aspirin, 160 mg of acetaminosalol (Salophen) and 15 mg of caffeine. For many people, a Sorojchi Pill every eight hours, particularly in combination with 400 mg of ibuprofen (Advil, Motrin, Nuprin), can help ward off the worst symptoms of altitude sickness.
• Take it very slow and easy at first. Over exertion can trigger altitude sickness
• Drink lots of bottled water or herbal or coca tea.
• many hotels offer oxygen, particularly in Cusco.
• don't eat heavy meals or drink alcohol, which can dehydrate your system. Wait a day or two. 
• Travel to lower altitude if you’re sick. If you’ve got altitude sickness or feel it coming on, going to the Sacred Valley can provide some quick relief if you're in Cusco.