Adapted from http://islam.about.com/od/prayer/qt/DuaSickness.htm
A’oodhu billaahi wa qudratihi min sharri maa ajidu wa uhaadhiru.
I seek refuge in Allah and in His power from the evil of what I experience and of what I guard against
allahuma rabbi-nas adhhabal ba’sa, ashfi wa anta al-shafi, la shifa’ illa shifa’uka shifa’ la yughadiru saqama.
Oh Allah! The Sustainer of Mankind! Remove the illness, cure the disease. You are the One Who cures. There is no cure except Your cure. Grant us a cure that leaves no illness.
Rabbana aatinaa fid dunya hasana wafil aakhirati hasana wa qinaa ‘adhaaba al-naar.
Oh Allah! Our Lord and Sustainer! Grant us good in this world and good in the Hereafter, and save us from the fire of Hell.
Asalu Allah al ‘adheem rabbil ‘arshil adheem an yashifika.
I ask Allah, the Mighty, the Lord of the Mighty Throne, to cure you.