The CQC carried out an unannounced focused inspection in March of York Hospital to follow up on significant safety concerns received about the standard of care patients were receiving.
It has told York and Scarborough Teaching Hospitals NHS Foundation Trust it must make urgent improvements and served it with a warning notice.
The hospital is used by many Scarborough-area patients and visitors.
The CQC issued the trust with a warning notice in response to its ineffective systems for managing patient risk assessments, nutrition and hydration, pressure area care and falls prevention.
Sarah Dronsfield, the CQC's head of hospital inspection said hospital staff were found to treat patients with "compassion and kindness" but did not always respect their privacy and dignity.
She continued: "The service didn't have enough nursing staff with the right skills, training and experience to keep patients safe and to provide the right care and treatment. It was disappointing that managers didn’t regularly review the situation and change the staffing arrangements to accommodate this.
"We found staff didn't always complete and update risk assessments for each patient or minimise risks to them.
"Also, staff didn't always make sure patients had enough to eat and drink, including those with specialist nutrition and hydration needs. This could put people at serious risk of harm, and we raised this with the trust at the time of inspection.
"Due to our findings, we have served the trust a warning notice so its leaders are clear about what changes must be made to improve patient care and safety. We will continue to monitor the service to ensure people are receiving safe care."
• The service did not always have enough staff on wards to allow them to take account of patients' individual needs, or help patients understand their conditions.
• Staff were unable to deliver fundamental standards of care within a timely way. Also, they were not appropriately or consistently assessing and managing risks to patients.
• Governance systems and processes failed to mitigate the risks identified in relation to nutrition and hydration, pressure area care and falls.
• Although staff had training in key areas including safeguarding, they did not always make referrals when required.
• Staff did not always support patients to make informed decisions about their care and treatment. They did not always follow national guidance to gain patient consent or make decisions in the best interests of those who lacked capacity.
The service was not rated and its rating has been suspended. The overall rating for the Trust remains "requires improvement".