I've always found it a bit difficult to fit 2 people in a toilet cubicle! I've never asked anyone to inject in a toilet while working as a nurse or at any other time. However, in the 14 years I've needed insulin (started several years after qualifiying as RGN, and after graduating with BSc in different topic), I have preferred, on occasions, to inject in private / out of sight of anyone else, eg soon after starting a new job and waiting for the right moment to tell colleagues, which often means a toilet or stockroom. However, I've also injected in the open air on many occasions - and it's only tricky when wearing salopettes and waterproof jacket, making it difficult to get to abdomen or thighs or arms.