The 53-year-old was taken in this morning and received medical treatment. In a brief statement issued on the club website, Hearts said he is doing well but is still in hospital.
There is no timescale for Levein's recovery and his assistant, Austin MacPhee, has been placed in charge of the Hearts first team until the manager returns.
"Heart of Midlothian Football Club can confirm that manager Craig Levein was taken to hospital this morning," said the statement. "Having received medical treatment, Craig is now recovering well in hospital.
"No further comment will be made at this time and the club asks that Craig and his family’s privacy be respected, as we all wish him a speedy recovery."