The U’s head coach felt light-headed and dizzy during the final half an hour of the draw at home against Derby County on Tuesday night, and left the stadium soon after the full-time whistle.
Buckingham was well-rested overnight and felt better on Wednesday, when United’s players and coaching staff were on a pre-planned rest day.
He then took training as per usual yesterday, as the U’s prepare for their trip to Championship pacesetters Sunderland this weekend.
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Buckingham said: “I’m alright, I’m okay. I went a little bit light-headed on Tuesday and chose to remove myself, and sit back in the dugout a little bit more than I would in the second half.
“I didn’t want to make a scene if I fell over in the technical area, but I managed to get through the game and then just decided not to hang around afterwards, just to make sure everything was done the way it should be and not be in the way of it.
“I removed myself and checked myself out, and had a good night’s sleep. I was looked after well and then came back in.”
League leaders Sunderland have won their last two games, both on the road, with a 1-0 victory at Hull City on Sunday backed up with a 2-1 win at Luton Town on Wednesday night.
Buckingham said: “It’s another big one, and one we’ll try and enjoy. It’ll be a wonderful atmosphere up there, and they’ve come off the back of two good away wins, and they’re a good team. They’ve shown that.
“We’ve shown already we’re sitting in a good place in the league, and we’ve shown the type of football we want to play, and we’ve shown when we play against teams like Sunderland that we try to give as best account of ourselves as we can.
“We’ll do exactly the same going up there in front of what will be a very good crowd.”
He added: “I think the table will keep chopping and changing every week. We’re seeing that with how tight the table actually is.
“Sunderland are on a good run, we know that, but I think in context, so are we.
“What I’ve been pleased with when we’ve come up against some of the teams like Burnley and West Brom, we’ve given a good account of ourselves, and that’s all I can ask going into this weekend.
“We know it’ll be a tough ask, but they’re all tough asks, and that’s the excitement at working at this level.”