The former England worldwide made the announcement at United's press conference on Monday ahead of the Champions League last-16, second-leg match against Sevilla.
"There comes a time when as much as you don't like it, it's time to stop playing football", Carrick told a press conference ahead of United's Champions League round-of-16 second leg against Sevilla.
"That's pretty much where I am at".
The 36-year old joined Manchester United in 2006 from Tottenham Hotspur for £18m has played only four times this season due to a heart trouble. We're still talking about it, to be honest, so there's nothing totally confirmed as yet.
"It's kind of been sorted", added Carrick.
He also confirmed that working under Mourinho next season was "looking likely".
European Union sanctions over Ukraine prolonged until Sept 15
It said the measures were due to "actions undermining or threatening the territorial integrity, sovereignty and independence of Ukraine".
Carrick underwent a procedure earlier in the season to treat an irregular heart rhythm.
"There were two or three times when I wondered whether it was worth still playing, but I soon got over that".
"I understood that I wouldn't be playing as many games, but I've been training hard and trying to keep fit".
"I wanted to finish on my own terms so I was determined to get back fit".
He has scored a total of 24 goals for Manchester United, who are now placed at the second position in the league, 13 points behind leaders Manchester City.