The James Paget Hospital in Norfolk has received its third official warning about the standard of care within the last year.
The Care Quality Commission's raised concerns about how well the trust was assessing the needs of patients.
The CQC also said the trust wasn't doing enough to make sure patients are receiving appropriate treatment. The James Paget has until the end of May to improve.
Cathryn Barmham, from the Care Quality Commission, said: "There are a number of actions we can take in respect of enforcement but the trust are making improvements and they are realising the significance of the concerns they have and as you are aware there have been personnel changed recently."
More top news
Anglia Weather: Frosty start with sunshine later
Becoming clear and frosty overnight. Bright and dry on Monday.
An Essex councillor is appealing for help to find out what happened to her "beautiful, much-adored" daughter after she was found dead.