A spokesperson for GMB told Yahoo UK: "Susanna has a pre-planned week off this week and is due back on Monday 27th June 2022."
The 51-year-old TV presenter - a single mother to three teenage sons Sam, Finn and Jack - has remained quiet on social media.
Reid worked throughout the coronavirus pandemic presenting Good Morning Britain under social distancing restrictions with former host Piers Morgan, and his subsequent roster of replacements after he quit the show in March 2021.
She is most often absent from the show during the school holidays and does not work on Fridays.
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One viewer tweeted: "Where is Susanna, this morning I just hope she’s okay so fabulous absolutely sensational lovely Susanna Reid?"
Another said: "No beautiful Susanna Reid this Monday morning, she is usually on presenting with Richard. I truly hope she is ok, she is missed by a lot of us GMB viewers."
Another GMB viewer joked: "Ok..where's m'Reid? Double checked, it's Monday, don't think it's school hols yet.. I'm all discombob'd! Ranvir's great, not that but is Susanna ok? It's definitely Mon& not Fri isn't it or have I slept through the week, missed my birthday & probably sacked?!"
Madeley, 65, is most often Reid's co-host on Good Morning Britain, but since Morgan left the show he has not been given a permanent replacement.
Instead Reid is joined by a rota of various presenters, including self-proclaimed Money Saving Expert Martin Lewis, Adil Ray, former politician Ed Balls, Ranvir Singh, Richard Bacon, Kate Garraway and temporarily former BBC Breakfast host Bill Turnbull.
Morgan, 57, is now hosting his own show Piers Morgan Uncensored, on global channel talkTV from Rupert Murdoch's News Corp.
While the outspoken TV presenter has signed a three year contract, viewing figures for his show have plummeted since it launched in April.