Ibrahim Halawa has told his family he is waiting on the death rope in jail in Egypt.
The 19 -year-old Dubliner has revealed he has been on hunger strike for more than 20 days.
He is been awaiting trial for over two years after being arrested in Cairo at a time when protests were taking place in the city.
He is due back in court next Month.
Ibrahim's sister Somaia has said the letter is a direct appeal to the Irish and Egyptian Government's for help.
She also said her family is increasingly concerned about his welfare.