The pair, played by Georgia Taylor and Ben Turner, will both make their departures later this year and show bosses have promised that they have a dramatic exit storyline in store.
Ruth and Jay bow out before Christmas and their final episode has been billed as "explosive and heart-stopping", holby.tv reports.
Meanwhile, a Casualty spokesperson told Digital Spy today: "After four action-packed years playing Dr Ruth Winters in Casualty, Georgia Taylor has decided to leave the show.
"Georgia is a brilliant actress and we cannot thank her enough for her fantastic work portraying Ruth's numerous highs and lows. We wish her the very best for the future and, although we know our viewers are going to miss her, we don't think they'll be disappointed with the character's extremely dramatic exit later this year!"
"Casualty is currently introducing a wave of new talent to the show including Michael Obiora, Madeleine Mantock, Charlotte Salt and Oliver Coleman and there will be some very exciting changes to Holby's emergency department as the programme switches to HD in the New Year."
Casualty continues tomorrow at 9pm on BBC One.
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