If you're heading for high places like the mountains, make sure you're prepared for the altitude change.
The decreased oxygen in the air at higher altitudes can cause altitude sickness. Symptoms can include headache, breathlessness with mild exertion, fatigue, nausea and disturbed sleep. To avoid this:

START SLOWLY. Begin at an altitude below 9,000 feet.

ALLOW TIME TO ADJUST. Rest a day after arriving to help you get used to the altitude.

TAKE IT EASY. High altitudes make normal activities more difficult. Slow down if you're out of breath or tired.

LIMIT ASCENT. Don't climb more than 3,000 feet in a day (1,000 feet if you're at 12,000 feet or above).

SLEEP AT A LOWER ALTITUDE. If you're above 11,000 feet during the day spend your nights at 9,000 feet or lower. At high altitudes your blood oxygen level may fall even lower when you sleep.

AVOID CIGARETTES AND ALCOHOL. Both can aggravate symptoms.

CONSIDER MEDICATION. Ask your doctor about acetazolamide (Diamox). This prescription medication my help prevent or lessen symptoms.

Altitudes sickness usually isn't serious. However, immediate descent and emergency medical care are necessary for sever altitude sickness.