Could Over Dosage Of Codeine Be A Matter Of Concern?

Was taking 1mg prednisolone for polymyalgia, having gradually reduced dose. Doc rang today to confirm blood test shows it s returned so prescribed 15mg in form of 5mg tabs. I was so desperate to start new dose as I ve been struggling to function with muscle stiffness so instead of fetching new prescription itook 15 of the 1mg tablets! By total mistake I had taken 15 codeine (well 12 actually as three were still in my hand). They were iin samekind of pack and same size. I been drinking loads of water all day and apart from feeling a bit sickly on and off I been absolutely fine . Should I be worried or won t it do any harm as a one off mistake? Not taken any other medication today as didn t want to upset my system anymore!