Sanskrit mantras for healing have been used for centuries for healing purposes. Here are a few powerful ones:
ॐ लं वं रं यं क्षं हं सं मातंगिनी स्वाहा ( ॐ Lam Vam Ram Yam Ksham Ham Sam Matangi Svaha )
You can simply recite this mantra for yourself or you can recite it over water and have the person who needs healing drink that water. In some cases the person may experience complete relief from illness, in others the intensity of the health problem may be reduced. You should always use healing mantras in conjunction with recommendations from your medical practitioner.