Fletcher was diagnosed with ulcerative colitis in November 2011 and has played just 13 matches since then as he continues to battle against the condition.
The 29-year-old has undergone several operations in that time, including his most recent procedure in January, and has been put on a strict dietary regime in an effort to return him to action.
Fletcher returned to training last week and was able to play 67 minutes in the United youth team's 2-2 draw with Fulham this evening.
"I've been training for a few weeks now and the next progression is to get some match-time. I enjoyed it," Fletcher told MUTV.
"The plan was to get to half time and see how I felt. Then get to 60 minutes and take it from there and, although I felt I could have gone on a bit longer, the plan was not to play more than that so I'm better sticking to the plan and not upsetting the sports science lads."
The Scotland international also paid tribute to the club and his family for keeping him going during the tough period.
"They've been great, especially the doc Steve McNally. He's worked closely with me, getting myself right and back, and the support from the club has been fantastic - from Sir Alex Ferguson to the new manager and David Gill. Everyone at the club. I couldn't ask for anything better.
"It's been tough. Luckily, I've got a great family around me - my wife, children, mum, dad and sisters. It's a great family and, if it was not for them, I wouldn't be standing here today.
"They keep me going, keep me motivated and lift me when I'm down. All these factors contributed to me standing here today on the road to recovery."
Fletcher joined United in 2002 and has made 312 appearances for the club in all competitions.