Altitude sickness (or Acute Mountain Sickness) is a condition caused by ascending too quickly and not allowing the body time to adjust to the reduced oxygen and changes in air pressure. This causes hypobaric hypoxia: a lack of oxygen reaching your body’s tissue. Symptoms typically begin to show above 2,500m if a person has not allowed their body time to adjust to the change in altitude. Symptoms of mild altitude sickness include dizziness, fatigue, headaches, nausea and vomiting, loss of appetite, a rapid pulse, and/or shortness of breath. More serious symptoms can include chest tightness, confusion, coughing, social withdrawal, trouble maintaining consciousness, a change in complexion or skin colour, difficulties walking, and eventually the risk of coma or death.