As far as Bhutan and Nepal is concerned, you don’t have to worry as you will be travelling well below 3000m. In Nepal the highest point you will reach is Sarangkot Hill(1600m), and in Bhutan the highest elevation you will hike to is Taktsang Monastery at 3100m. You will be spending very little time at these places, so you won’t face any discomfort. Tibet, known as the world’s highest country, lies above an elevation of 3,500m. Thus it is natural to feel out of sorts immediately after your arrival as the air in Tibet is thin. In order to let your body adjust, we have not included any activities on the first day. You need to rest at your hotel. Drink lots of water as dehydration triggers altitude sickness.  If you have difficulty in breathing you can ask for medical advice and take supplementary oxygen (available at almost all hotels and pharmacies). Our tours are comfortably paced and physically not strenuous. Having said that it would be advisable for you to consult your physician before you book this trip, especially if you suffer from respiratory or heart disorders.