Sherbrooke Lodge Care Home in Pollokshields was graded "weak" and "unsatisfactory" in all areas - the two lowest grades inspectors can award.
The Care Inspectorate has served a formal Improvement Notice on the home, with particular concerns raised about staffing and the nutrition and hydration of residents.
The report said the health and wellbeing of residents was being "compromised" due to a lack of urgency by the management team.
Inspectors raised serious concerns about the home last August following a previous inspection and made 24 improvement recommendations. But in a snap inspection in February, they found that only two had been met.
During the latest inspection, staff found the quality of management and leadership had deteriorated even further, leading to the home being graded "unsatisfactory" or "weak" in all areas .
Dr Robert Peat, Director of Inspection, said: "We identified a lack of urgency in the approach of the management team, with key areas not prioritised.
"Residents' health and wellbeing were compromised as a result.
"We could not find evidence that there was adequate management and monitoring of the home.
"This was particularly concerning given the outcomes of the last inspection. We have therefore taken urgent action to support the home to improve and our inspectors are in the home this week.
"We are working closely with the local authority and health colleagues to support improvement but will not hesitate to take further action if improvement is not made and sustained quickly."