Aims: β‐cell stress and dysfunction may contribute to islet autoimmunity and progression to clinical type 1 diabetes. We present a protocol of three randomised controlled trials assessing the effects of glucagon‐like peptide 1 (GLP − 1) analogue liraglutide in three early stages of type 1 diabetes. Methods: We will test 10‐ to 30‐year‐old people with multiple islet autoantibodies for their glucose metabolism and randomise participants with stage 1 (multiple islet autoantibodies and normoglycaemia), stage 2 (multiple islet autoantibodies and dysglycaemia) and early stage 3 (clinical diagnosis) type 1 diabetes, 10−14 persons in each, to a 6‐month intervention with liraglutide or placebo with 6‐month follow‐up in the stage 2 and stage 3 trials and 18‐month follow‐up in the stage 1 trial. Primary efficacy outcome in the stage 1 and stage 2 trials is a first‐phase insulin response in an intravenous glucose tolerance test and C‐peptide area under the curve in a 2‐h mixed‐meal tolerance test in the stage 3 trial. In addition, safety and tolerability of liraglutide treatment will be assessed. Conclusions: Most prevention trials of type 1 diabetes have targeted the immune system. Treatment with GLP‐1 analogue liraglutide supports the pancreatic β‐cells, which should likewise attenuate islet autoimmunity. Our innovative study design allows simultaneous investigation of an intervention in three groups of people who represent various early stages of type 1 diabetes and maximises the eligibility to participate. Trial registration: NCT02611232 (stage 1 trial), NCT02898506 (stage 2 trial), NCT02908087 (stage 3 trial). [ABSTRACT FROM AUTHOR]