The club have released no further details on the condition of the 49-year-old former Tottenham defender.
An Orient statement read: “Leyton Orient can confirm head coach Justin Edinburgh was taken to a local hospital on Monday morning after being taken ill unexpectedly.
“The club will be making no further comment at this time and requests that the family’s privacy is respected.”
Edinburgh, who has also managed Newport, Gillingham and Northampton, took over at Orient in November 2017 and guided the club to promotion back to the Football League last season.
Tottenham tweeted: “Everybody at the Club sends their best wishes to our former defender Justin Edinburgh after he was taken ill earlier this morning.”
Edinburgh played for Tottenham 10 years and has been managed at Orient since 2017.
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