As a general rule: Assume acute mountain sickness (AMS) unless proven otherwise. AMS is potentially life threatening, so if you have symptoms related to AMS, do not ascend any further. If they do not get better, descend. Low altitude is not an indication against AMS which can occur above 2000m already. So the assessment should rely on your symptoms. Early symptoms of AMS are [\[1\]][1] - Difficulty sleeping - Dizziness or light-headedness - Fatigue - Headache - Loss of appetite - Nausea or vomiting - Rapid pulse (heart rate) - Shortness of breath with exertion Obviously, the last two occur anyway at high altitudes, so you have to judge whether it is pathological. To help asses how bad the condition is one can use the [Lake Louis Score][2]. This is not a definitive diagnosis, but a way to objectively judge your condition. This is fairly conservative, so if you follow this advice you should never get into a situation where you develop more advanced symptoms, High-altitude cerebral edema (HACE) or High-altitude pulmonary edema (HAPE). The latter two are actually symptoms of AMS which are directly live threating and therefore often referenced as conditions of their own. Advanced symptoms include: [\[1\]][1] - Blue color to the skin (cyanosis) - Chest tightness or congestion - Confusion - Cough - Coughing up blood - Decreased consciousness or withdrawal from social interaction - Gray or pale complexion - Cannot walk in a straight line, or walk at all - Shortness of breath at rest If you experience these, the condition is already life threatening and you need to descend asap. The usual case is, that you have a mild form of AMS not including any advanced symptoms and you need to make a decision on how to proceed. This depends a lot on logistical factors: Where are you, where do you want to go and how easy can you descend. If your plans allow it, the best option is always to stay and see how the symptoms progress. If you need to go on, you have to factor in escape plans. Assuming you can easily descend, going on is save, just keep track of the symptoms and react accordingly. If going on means committing for a push into an area where the only way out is walking, the save way to go is aborting. The symptoms can get worse fast and impact your ability to walk out severely. This means you will stay longer at high altitude which again makes the AMS worse. Source: \[1\] J. Heller, *Acute Mountain Sickness*, 18.10.2015, [https://www.nlm.nih.gov/medlineplus/ency/article/000133.htm][1]. [1]: https://www.nlm.nih.gov/medlineplus/ency/article/000133.htm [2]: http://www.treksafe.com.au/medical/documents/LakeLouisescore_000.pdf