[header] How to treat mild altitude illness [title] Descend to a lower altitude. [step] If you start to experience any symptoms of mild altitude sickness, such as a headache, lightheadedness, or lung pain, you should descend by at least 500 m or 1 , 600 feet. This will give your body time to acclimatize to the altitude and relieve your symptoms. 
[substeps] You should avoid attempting to go to higher altitudes for two to three days, or until your symptoms have disappeared. Severe altitude sickness can be fatal, so if you notice your symptoms getting worse, make sure you descend to a much lower height.