Symptoms of altitude sickness may include headaches, vomiting, tiredness, confusion, trouble sleeping, and dizziness.

[2][4] Risk factors include a prior episode of altitude sickness, a high degree of activity, and a rapid increase in elevation.

Symptoms often manifest within ten hours of ascent and generally subside within two days, though they occasionally develop into the more serious conditions.

[citation needed] Those individuals with the lowest initial partial pressure of end-tidal pCO2 (the lowest concentration of carbon dioxide at the end of the respiratory cycle, a measure of a higher alveolar ventilation) and corresponding high oxygen saturation levels tend to have a lower incidence of acute mountain sickness than those with high end-tidal pCO2 and low oxygen saturation levels.

Symptoms include fatigue, severe dyspnea at rest, and cough that is initially dry but may progress to produce pink, frothy sputum.

Extreme hypoxemia may occur during exercise, during sleep, and in the presence of high altitude pulmonary edema or other acute lung conditions.

[11] The physiology of altitude sickness centres around the alveolar gas equation; the atmospheric pressure is low, but there is still 20.9% oxygen.

Some severe cases may require professional diagnosis which can be assisted with multiple different methods such as using an MRI or CT scan to check for abnormal buildup of fluids in the lung or brain.

Examples of pre-acclimation measures include remote ischaemic preconditioning, using hypobaric air breathing in order to simulate altitude, and positive end-expiratory pressure.

[17] Once above approximately 3,000 metres (10,000 ft) – a pressure of 70 kilopascals (0.69 atm) – most climbers and high-altitude trekkers take the "climb-high, sleep-low" approach.

This process cannot safely be rushed, and this is why climbers need to spend days (or even weeks at times) acclimatizing before attempting to climb a high peak.

[19] The drug acetazolamide (trade name Diamox) may help some people making a rapid ascent to sleeping altitude above 2,700 metres (9,000 ft), and it may also be effective if started early in the course of AMS.

[23] Acetazolamide, a mild diuretic, works by stimulating the kidneys to secrete more bicarbonate in the urine, thereby acidifying the blood.

This change in pH stimulates the respiratory center to increase the depth and frequency of respiration, thus speeding the natural acclimatization process.

[27] The CDC advises that Dexamethasone be reserved for treatment of severe AMS and HACE during descents, and notes that Nifedipine may prevent HAPE.

[29] Interest in phosphodiesterase inhibitors such as sildenafil has been limited by the possibility that these drugs might worsen the headache of mountain sickness.

[30] A promising possible preventive for altitude sickness is myo-inositol trispyrophosphate (ITPP), which increases the amount of oxygen released by hemoglobin.

Prior to the onset of altitude sickness, ibuprofen is a suggested non-steroidal anti-inflammatory and painkiller that can help alleviate both the headache and nausea associated with AMS.

[14] Indigenous peoples of the Americas, such as the Aymaras of the Altiplano, have for centuries chewed coca leaves to try to alleviate the symptoms of mild altitude sickness.

Stationary oxygen concentrators typically use PSA technology, which has performance degradations at the lower barometric pressures at high altitudes.

There are also portable oxygen concentrators that can be used on vehicular DC power or on internal batteries, and at least one system commercially available measures and compensates for the altitude effect on its performance up to 4,000 m (13,000 ft).

Increased water intake may also help in acclimatization[35] to replace the fluids lost through heavier breathing in the thin, dry air found at altitude, although consuming excessive quantities ("over-hydration") has no benefits and may cause dangerous hyponatremia.

The only definite and reliable treatment for severe AMS, HACE, and HAPE is to descend immediately until symptoms resolve.

[36] Attempts to treat or stabilize the patient in situ (at altitude) are dangerous unless highly controlled and with good medical facilities.

However, the following treatments have been used when the patient's location and circumstances permit: Tourists and mountain climbers are two groups of people who typically contract elevation sickness.

[43] A 2017 study found that contrary to Chile both the United States and Peru lacked legislation regarding altitude sickness in mining operations.