Woodside House Care Home, in Ayrshire, was found to have an "unsatisfactory" level of care in every area inspected.
The Care Inspectorate has served a formal Improvement notice on the home in Mauchline, East Ayrshire.
It is currently closed to new admissions and the Care Inspectorate is working closely with the home to make the required changes. A spokesman said: "Our inspectors found several areas of significant concern.
"The quality of care was simply not acceptable.
"Every person has the right to safe, high-quality, compassionate care that meets their needs and respects their rights.
"We require significant improvements to the medication system within the next six weeks, including storing medicines safely."