The global population is ageing, and increasingly developing long-term conditions and comorbidities associated with functional changes, reduced quality of life and reduced life expectancy. Diabetes mellitus is a common long-term condition in older people, with many individuals experiencing microvascular and/or macrovascular complications, alongside frailty and dementia. Symptoms of conditions such as hypoglycaemia and hyperglycaemia may change as a result of older age and long duration of, and complications associated with, diabetes; therefore, such symptoms can be challenging to recognise in older people. Consequently, treatment might be delayed, which can result in further deterioration and harm for older people. Managing diabetes is often challenging for older people with the condition and their family carers and nurses. One of the main challenges for healthcare professionals is deciding safe blood glucose and glycated haemoglobin ranges for the individual to avoid over-treatment that can lead to hypoglycaemia or under-treatment that can lead to hyperglycaemia and associated adverse effects. This article outlines the issues that nurses should consider when caring for older people with diabetes, and emphasises the importance of personalised care.