If You Are Headed to Higher Altitudes to Avoid the Heat, You Should Know About High Altitude Illness

Many years ago, while en route to Everest Base Camp, a fellow hiker began to experience headache, nausea, and lightheadedness. By the time he reached Lobuche (elevation 16,110’) he was having difficulty breathing. Fortunately, other members of the group recognized the symptoms of high altitude illness (HAI) before they progressed further, and he was taken to a lower elevation to recover.

Travelers to extreme altitudes such as the Himalayas are usually aware of the risk of developing HAI, but HAI can occur at much lower altitudes. Mild HAI symptoms can develop at elevations as low as 5000’ and mild to moderate HAI becomes common above 8200’. Severe HAI can also occur at this elevation but it is more common above 9800’.  For comparison, Phoenix is at an elevation of 1,086′, Tucson is 2,388′, Prescott is 5367’, Show Low is 6345’, Flagstaff is 6906’, the Grand Canyon (North Rim) is 8,297’, Mt. Lemmon is 9,160’, Mt. Baldy is 11,409’, and Humphries Peak is 12,637’.

As Summer temperatures in the lower regions of Arizona rise, recreationalists often seek the cooler temperatures of higher elevations for hiking, camping, mountain biking, and other outdoor activities. HAI can affect anyone who travels to a higher altitude without giving the body sufficient time to adjust to changes in air pressure and oxygen levels. The more rapid the change in altitude, the more likely HAI will occur. HAI also is more likely to develop with activities that require exertion. People who live at lower elevations and are not used to higher altitudes have a greater risk of HAI. If you are heading to higher altitudes to escape the Summer heat, it is important to know the signs and symptoms of HAI and how to prevent and treat it.

Mild symptoms of HAI include headache, nausea, vomiting, lightheadedness, fatigue, loss of appetite, and difficulty sleeping. Symptoms appear 12 to 24 hours after exposure to high altitude and lessen after a few days as the body adapts to the decreased oxygen. Moderate HAI is characterized by worsening of  the previous symptoms, plus weakness, shortness of breath, tightness in the chest, and loss of coordination. Normal activities may become difficult. Moderate HAI can usually be resolved by a few days at lower elevation, after which returning to higher elevations can be safely attempted. Symptoms of severe HAI include increased shortness of breath, a productive cough, inability to walk, confusion, and edema of the lungs and brain. Severe HAI is an emergency and requires immediate return to a lower altitude.

The best way to prevent HAI is by increasing altitude slowly to allow the body time to acclimate. Other preventative measures include avoiding tobacco, alcohol, or any drug that reduces respiratory rate; drinking at least 3 quarts of water a day; and eating a diet that includes 70% carbohydrates. If you experience symptoms of HAI, move to a lower altitude until they resolve.

While the primary treatment for HAI is returning to a lower elevation, mild HAI symptoms can be treated with over-the-counter medication. Acetazolamide, a prescription medication that increases respiratory rate, can also be used to treat minor symptoms of HAI. Moderate HAI should improve within 24 hours at a lower elevation and resolve completely within 3 days. Severe HAI requires immediate medical attention and usually hospitalization. If traveling above 10,000’, dexamethasone can be carried for emergency treatment of edema of the lungs and brain.


Carod-Artal, F.J. (2014). High-altitude headache and acute mountain sickness, Neurología (English Edition), 29, 533-540. doi.org/10.1016/j.nrleng.2012.04.021.

Gallagher, S.A., Hackett, P., & Rosen, J.M. (2015). High altitude illness: Physiology, risk factors, and general prevention. Uptodate. Retrieved from https://www.uptodate.com/contents/high-altitude-illness-physiology-risk-...


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