Acorn Park Care Home in East Kilbride, South Lanarkshire, was warned it must make a "significant improvement".
If not, it could face having its registration cancelled.
The privately-run home was served with a formal improvement notice by the Care Inspectorate and given until next month to make changes.
Seven areas of concern were listed after an inspection, with nutrition and hydration, personal plans for service users, environmental safety, staffing and administration of drugs all being criticised.
A spokesman for the Care Inspectorate said: "Everyone in Scotland has the right to safe, compassionate care which meets their needs and respects their rights.
"Where we have concerns, we do not hesitate to take action.
"Our first priority is always the safety and well-being of residents and this improvement notice sets out what we expect the service to do to ensure that the care provided to residents improves.
"We will be inspecting this service again soon to ensure that progress is being made."
An Acorn Park spokesman said: "We are working hard with the Care Inspectorate to meet their requirements within the timescales set."
A care home has been ordered to raise its standards after the industry watchdog criticised areas including infection control.