"Amy was admitted to the UCLH this morning, suffering from severe exhaustion. She was discharged this afternoon and has been advised to take complete rest. All scheduled performances are now postponed," the Daily Mail quoted Shane O'Neill, a spokesperson for the star's record label Island/Universal, as saying.
Winehouse initially sparked concerns for her health after she cancelled a string of concerts last month, citing "exhaustion" and was ordered by doctors to take rest.
The Rehab singer was lined up for the Oya music festival in Oslo, Norway, on August 7.
Organisers of the Oslo festival said they were told of the latest cancellation only a few hours before she was due to perform.