INTRODUCTION: Type 2 diabetes (T2D) is a progressive disease with increasing prevalence in most countries. The majority of patients with T2D have inadequate glycaemic control, which increases the risk of diabetic complications later in life. New therapies with improved safety profiles are required to tackle the progressive nature of T2D. Areas covered: The efficacy and safety profile of IDegLira - a once-daily, fixed-ratio combination of insulin degludec and liraglutide, a glucagon-like peptide-1 receptor agonist (GLP-1RA), for the treatment of T2D - has been extensively evaluated. IDegLira's phase 3 clinical trial programme builds upon the clinical programmes of its mono-components, and their cardiovascular outcomes trials. The results are described here, focusing on different patient populations and compared with alternative insulin regimens. Expert opinion: IDegLira provides superior glycaemic control and mitigates the primary adverse effects associated with insulin therapy (weight gain and hypoglycaemia) and GLP-1RAs (gastrointestinal side effects) with no indication of additive effects. Accordingly, co-formulations such as IDegLira are likely to be increasingly preferred over stepwise addition and titration of the individual agents in the management of T2D.