You should visit your doctor and dentist for a check-up prior to taking your trip to Bhutan and seek specific advice. The following is a rough and basic guide for immunization. Upon advance notice, your doctor will be able to administer all the above vaccinations.
Lhasa - Mt. Kailash - Guge Kingdom
Lhasa, Everest Base Camp and Kathmandu
Sacred Yatra of Kailash and Mansarovar (Heli)
Nam Tso Lake and Nyenchen Thanglha