Safety comes first. Normally when you go to high Himalayas, you have to be physically fit. It is good to do regular exercise at least 3 months in advance. On your arrival to Kathmandu also we brief you about altitude sickness in the case you go on high altitude. So, please follow the instruction carefully. On top guide suggests you while you are on field.
Following the instruction there is less chances of getting sickness but there is no guarantee. We also have days of acclimatization when you go high mountain. We hike up hill and come and rest in low altitude. Altitude sickness can be serious problem when you go on high mountain and in case you become sick. We will take the best measure to come down. We do all the evacuation whatever is appropriate but bill comes to you.
In the case you have some chronical disease. It is good to consult the doctor at home and inform doctor that you are going to trek in Himalayas and if possible give the highest point of your travelling.
No doubt Supporter Treks and Tours always provide you best service but in case of sickness and injuries we try help to solve the problem in your own risk. So, it is good to be insuranced before you travel to Nepal.