The 44-year-old, who played for Aston Villa and Middlesbrough and was capped by England on four occasions, received medical attention at Tottenham's Enfield training base before he was transferred to hospital in an ambulance.
According to reports, Ehiogu suffered a suspected heart attack.
Tottenham said via their Twitter account on Thursday: ''We can confirm that Ugo Ehiogu is currently in hospital after collapsing at our Training Centre earlier today.
''Our Under-23's coach received immediate treatment on site from our medical staff before being transferred to hospital by ambulance.
''Everyone at the club sends their best wishes to Ugo and his family. We shall continue to provide updates when we have further information.''
England manager Gareth Southgate played alongside Ehiogu at Villa and Boro and the Three Lions led the messages of support to the former defender on Thursday evening.
"Sending our thoughts and best wishes to former #ThreeLions defender Ugo Ehiogu," they tweeted. Aston Villa, who Ehiogu played for during a nine-year spell with the Birmingham club, added: "Get well soon, @UgoEhiogu! Everyone at #AVFC wishing you a speedy recovery."
Ehiogu began his career as a trainee at West Brom before he was taken to Villa by Ron Atkinson in 1991. He went on to feature in more than 300 matches for Villa and played in their FA Cup final defeat against Chelsea in 2000.
Ehiogu joined Middlesbrough for a then club-record £8million fee later that year, and in 2001 he scored his only goal for England in Sven Goran-Eriksson's first game in charge, a 3-0 friendly victory against Spain.
Knee injuries plagued the final years of Ehiogu's career at the Riverside Stadium.
He joined Leeds on loan in 2006, and also had short spells with Rangers and Sheffield United before he retired from football in 2009. Ehiogu subsequently moved into coaching and has been with Tottenham for the past three seasons.
