(HealthDay News) -- Altitude sickness is triggered by the significantly lower amounts of oxygen in the air at higher altitudes. The condition often affects people who live at lower altitudes who travel to altitudes of 8,000 feet or higher.

The most common symptoms of altitude sickness are dizziness, lightheadedness, headache, weakness, insomnia and an upset stomach, says the American Academy of Family Physicians. People with severe symptoms should try to move to a lower altitude as soon as possible.

The academy suggests gradually climbing to a higher altitude, letting your body adjust to the difference in oxygen over several days. You should also try to sleep at an altitude that is lower than your altitude during the day, the AAFP advises.