This is a single centre, double-blind, randomised, three-period crossover phase 1 trial in subjects with type 1 diabetes mellitus (T1DM). Each subject will be randomly allocated to a sequence of three treatments, i.e. two single subcutaneous doses of BioChaperone® Glucagon (BC Glucagon) formulation 1, BioChaperone® Glucagon formulation 2 and GlucaGen® HypoKit®, each at the fixed doses of 50 µg and 1 mg on 3 separate dosing visits.