Duncan Bannatyne said he hoped to be discharged from hospital on Tuesday after being rushed in with a suspected heart attack.
The 63-year-old Dragons' Den star was in Darlington Memorial Hospital after he fell ill at the headquarters of his gym business in the town.
He was well enough to send messages from his bed to his 540,000-plus followers on Twitter, telling them: "Hi. In hospital attached to a few wires feeling tired but am sure I will be discharged tomorrow fit & well (fit as a pensioner can be anyway)."
And he followed it with: "Today was my first trip inside an Ambulance & with siren wailing. Hope it is the last. LoL"
Earlier a spokeswoman for the Bannatyne Group said: "Everyone at the company is very concerned and upset, but we know that Duncan is a very strong person and we are confident he will make a full recovery.
"Everyone wishes him well. We'd like to thank the quick and professional actions of the paramedics who attended to Duncan and thank the staff at the Memorial Hospital for his ongoing care."
Bannatyne, who lives on the exclusive Wynyard estate in the countryside north west of Middlesbrough, was born in Clydebank, Scotland and was raised in what he describes as "relatively modest circumstances".
His business interests now include health clubs, hotels, property, media and transport and he is best known as a tough-talking business angel on the BBC show Dragons' Den.
The former Royal Navy stoker began his empire with an ice cream van, rapidly expanding that business in tough competition before setting up a chain of care homes.
On his website he says he sold that for £26 million in 1996 and his children's nursery chain for £22 million.