Mild hypoxia occurs at which altitude?

• A. 5,000 ft
• B. 10,000 ft
• C. 15,000 ft
• D. 20,000 ft

Answer: (B)

As you rise, the air has less oxygen, so the body’s oxygen delivery to tissues starts to drop. Mild hypoxia means the first noticeable impairment in function from that reduced oxygen delivery. In aviation training and many practice tests, this early stage is considered to begin around 10,000 feet. At about this altitude, people often notice subtle effects such as slight headache, reduced alertness, or mild difficulty concentrating, especially with effort or fatigue. It marks the point where performance can begin to be affected but is typically not life-threatening with prompt recognition and rest or supplemental oxygen. Higher altitudes, like 15,000 feet and above, bring more pronounced symptoms (moderate to severe hypoxia) that impair function more significantly.