Health officials are now trying to trace where Dorries contracted the virus and who she has been in contact with, she added.
Dorries, who helped craft the legislation to fight the coronavirus, is the first British politician to be diagnosed with COVID-19, raising immediate concern about whether she has spread the infection.
The Times newspaper reported that she had been in touch with hundreds of people, including Prime Minister Boris Johnson.
She fell unwell on Friday while signing the document that declared coronavirus a notifiable disease, meaning companies could obtain insurance cover, said the paper, adding she was now believed to be on the road to recovery.
"I would like to thank ... the wonderful NHS staff who have provided me with advice and support," she said, referring to Britain's National Health Service.
The shock news is likely to increase calls to suspend parliament, despite the government's reluctance to do so in the middle of a health crisis.
Six people have died in Britain from the virus, with 373 confirmed cases.
Meanwhile, the Bank of England cut its key interest rate by 0.5 percent to 0.25 percent on Wednesday, as an emergency measure in response to the outbreak of COVID-19.
The central bank said the move would "help support businesses and consumer confidence at a difficult time".
The UK is due to announce more measures to support the economy in a budget later on Wednesday.