A new report has revealed that poor training and screening sees one care home resident with diabetes admitted to hospital every 25 minutes.
The Diabetes UK report found that 60% of care homes with diabetic patients in England do not train their staff on the condition.
The report - titled Diabetes in Care Homes: Awareness, Screening, Training - also showed that new residents were screened for diabetes at just 23% of care homes.
Furthermore, just 28% conducted screenings of patients each year.
Taking the missed screening into account, it is thought that around 13,500 people living in care homes could have undiagnosed type 2 diabetes.
Diabetes UK Chief Executive, Barbara Young, said: "These report findings are an indictment of the standards of diabetes care provided by a worrying number of our country's care homes.
"Even the most basic training and awareness can have a huge impact on improving the quality of life for thousands of society's most vulnerable people by preventing the complications of diabetes as well as reducing costs to the NHS."
Basic training for care home staff should include how to identify symptoms, recognise and treat hypoglycaemia ('hypos'), measure and monitor blood glucose levels, administer insulin safely, and understand the importance of dietary timings and requirements as well as regular physical activity.
Diabetes UK is calling for care homes to implement the recommendations in its guidance document Good Clinical Practice Guidelines for Care Home Residents with Diabetes.
This includes screening new residents for diabetes on admission and all residents at two yearly intervals; for all people with diabetes in care homes to have an individualised care plan tailored to their needs; and for all care home managers to put in place appropriate diabetes-specific training for all staff.
The charity also wants the Care Quality Commission (CQC) to make diabetes training part of any care home's registration requirements, and for every local commissioner of services to make an assessment of their local population's needs with regards to effective diabetes management in care homes.