Acclimatization at High Altitude

How Much Do You Know About Altitude Acclimatization?

Altitude Acclimatization Takes Time…

At sea-level, healthy people have an oxygen saturation (SpO2) level in the blood of 98-99%. When one goes to high altitude, the percentage of oxygen in the bloodstream goes down quite significantly—and prolonged exposure to these lower blood oxygen levels is the primary cause of the effects of altitude.

The major cause of altitude illnesses is going too high, too fast. Given time, your body can adapt to the decrease in oxygen molecules at a specific altitude. This process is known as acclimatization and generally takes 1-3 days (per atmosphere) at that altitude. For example, if you hike to 10,000 feet (3,048 meters), and spend several days at that altitude, your body acclimatizes to 10,000 feet (3,048 meters). If you climb to 12,000 feet (3,658 meters), your body has to acclimatize once again.

The Acclimatization Process

A number of changes take place in the body to allow it to operate with decreased oxygen:

  • • The depth of respiration increases.
  • • Pressure in pulmonary arteries is increased, “forcing” blood into areas of the lung not normally used during breathing.
  • • The body produces more red blood cells to carry oxygen.
  • • The body produces more of a particular enzyme that facilitates the release of oxygen from hemoglobin to the body tissues.
Oxygen Levels at High Altitude

How Long Does it Take to Become *FULLY* Acclimatized?

From sea level, here is the average amount of time it takes to become FULLY acclimatized to altitude:

  • 6,000 ft (1829 m) — 3 Weeks
  • 8,000 ft (2438 m) — 4 Weeks
  • 10,000 ft (3048 m) — 5 Weeks
  • 12,000 ft (3658 m) — 6 Weeks
  • 14,000 ft (4267 m) — 7 Weeks


Source: CDC – High Altitude Travel Directory