The United Lincolnshire Hospitals NHS Trust has been told it must take action to be sure it is meeting standards of quality and safety.
The independent watchdog, the Care Quality Commission (CQC), said the trust must look at four areas.
These include patients sometimes waiting in unsuitable areas after surgery and also not being given help to take medication.
The trust said they have already begun to take action on the issues raised.
The CQC carried out an unannounced inspection in June to assess compliance with new quality and safety standards, which came into effect in April.
Inspectors found patients waiting up to four hours in the theatre recovery area with no access to toilets, due to high demand for beds.
They also highlighted incidents of staff who left medication at patients' bedsides and did not give them help to take it when needed.
The report added that not all staff were clear about what to do if they suspected a patient was being abused, and not all had received training on the protection of vulnerable adults.
But inspectors emphasised the issues were not "immediate risks" to safety, and examples of good quality care were noted, including adequate staffing levels, staff enjoying their work, and staff knowing what to do if a patient's condition deteriorated.
A statement from the trust said it welcomed the commission's review.
"We have already begun work to address the areas where action needs to be taken," the statement said.
"We are pleased that the CQC has recognised that patient safety is always the trust's foremost priority and that we provide safe care to our patients."
The trust has now been asked to provide an action plan for rectifying the issues raised.