Medicine Buddha Mantra by Khenpo Pema Chopel Rinpoche
The mantra, or even the name of the Medicine Buddha (Skt: Bhaisajyaguru, Tib: Sangye Menla, Chin: Yaoshi-fo, Jap:Yakushi) is beneficial.
Ven. Thrangu Rinpoche has said that a mantra is essentially an elaboration on the deity's name, and that any mantra is the shortest possible form of the sadhana. The Sanskrit mantra of Medicine Buddha is:
Tayata, Om, Bhaishaye Bhaishaye Maha-Bhaishaye Raja Samudgate, Svaha.
or, pronounced the Tibetan way:
Tayata, Om, bekandzeh, bekandzeh maha-bekandzeh, radza samungateh. Soha.
'May all beings benefit from the sublime love and power of Sangye Menla' is often given as the meaning but it is not a literal translation.
Since the practice of Medicine Buddha is considered a Sutrayana practice (i.e., based mainly on scripture) no empowerment is necessary, but it is good to attend one or to ask for one when you have an opportunity.
Khenpo Karthar has said that the practice of Sangye Menla also has been found beneficial in cases of mental illness. And it is said that even hearing the name Sangye Menla only once has benefits for subsequent rebirth, for the Medicine Buddha made 12 vows describing the various ways he can help sentient beings with their sufferings.