Travel insurance is the most important things you should have before start travelling. A travel-insurance policy that covers lost & theft, medicals, evacuation from high altitude, adventure activities etc are the basic things you should have. There are a wide variety of policies available, so please make sure you check the small print carefully. Since you reach above 4000 meters on quite a few treks in Nepal, it is the best way of choosing a policy that covers medical and emergency evacuation, including helicopter evacuation and medical treatment. Also understand that most medical treatment and facilities/hospitals must be paid at the point of delivery of the patient. So it’s wise to choose a policy that pays doctors or hospitals directly rather than you having to pay on the spot and claim later.