The symptoms of altitude sickness

Mild altitude sickness (mild AMS)

The symptoms of mild AMS are not dissimilar to the symptoms of a particularly vicious hangover, namely a thumping headache, nausea and a general feeling of lousiness. An AMS headache is generally agreed to be one of the most dreadful headaches you can get, a blinding pain that thuds continuously at ever decreasing intervals; only those who have bungee-jumped from a 99ft building with a 100ft elasticated rope will know the intense, repetitive pain AMS can cause.

Thankfully, the usual headache remedies should prove effective against a mild AMS headache. As with a hangover, mild AMS sufferers often have trouble sleeping and, when they do, that sleep can be light and intermittent. They can also suffer from a lack of appetite. Given the energy you’ve expended getting to altitude in the first place, both of these symptoms can seem surprising if you’re not aware of AMS.

Moderate altitude sickness (moderate AMS)

Walking slowly on the mountain can delay/prevent the onset of AMS.

Moderate AMS is more serious and requires careful monitoring of the sufferer to ensure that it does not progress to severe AMS. With moderate AMS, the sufferer’s nausea will lead to vomiting, the headache will not go away even after pain-relief remedies, and in addition the sufferer will appear to be permanently out of breath, even when doing nothing.

With moderate AMS, it is possible to continue to the summit, but only after a prolonged period of relaxation that will enable the sufferer to make a complete recovery. Unfortunately, treks run to tight schedules and cannot change their itineraries mid-trek. Whether you, as a victim of moderate AMS, will be given time to recover will depend largely upon how fortunate you are, and whether the onset of your illness happens to coincide with a scheduled rest day or not.

Severe altitude sickness (severe AMS)

With severe AMS, on the other hand, there should be no debate about whether or not to continue: if anybody is showing symptoms of severe altitude sickness it is imperative that they descend immediately. These symptoms include a lack of coordination and balance, a symptom known as ataxia.

A quick and easy way to check for ataxia is to draw a 10m line in the sand and ask the person to walk along it. If they clearly struggle to complete this simple test, suspect ataxia and descend. (Note, however, that ataxia can also be caused by hypothermia or extreme fatigue. As such, ensure that the sufferer is suitably dressed in warm clothing and has eaten well before ascertaining whether or not he or she is suffering from ataxia, and what to do about it).

Other symptoms of severe AMS

Other symptoms of severe altitude sickness include mental confusion, slurred or incoherent speech, and an inability to stay awake. There may also be a gurgling, liquid sound in the lungs combined with a persistent watery cough which may produce a clear liquid, a pinky phlegm or possibly even blood. There may also be a marked blueness around the face and lips, and a heartbeat that, even at rest, may be over 130 beats per minute. These are the symptoms of either HACO and HAPO, as outlined in the next section.