Objective There have been concerns about the effects of antipsychotics on weight gain and the development of type 2 diabetes (T2DM). This article aims to provide an up-to-date review on the evidence addressing this issue and the practical implications for the management of people taking antipsychotics in the context of T2DM. Methods We carried out searches on MEDLINE/PUBMED and the ClinicalTrials.gov website in August 2017 using the terms ‘antipsychotic’ and ‘diabetes’ or ‘glucose’ citing articles published after 2006 preferentially. Results Antipsychotics are associated with T2DM and are likely to exert a causal effect of uncertain magnitude. Children and adolescents appear especially vulnerable to these metabolic effects; as T2DM is not common in healthy younger people, the relative risk is more apparent. Antipsychotics act on glucose and insulin homeostasis in a variety of direct and indirect mechanisms. To reduce the increasing health inequalities among individuals with mental illness screening, monitoring and prevention of T2DM is important, as is improved diabetes care in this population. Conclusion It remains unclear whether these antipsychotic medications exacerbate an underlying predisposition to the development of T2DM or have a direct effect. Potential risks need to be weighed up and balanced between improved and lasting mental health benefits and any detrimental physical health side effects. Achieving parity of esteem between mental and physical health is a worldwide priority if we wish to improve life expectancy and quality of life in people with severe mental illness.