On once daily injection, it was my legs. Twice daily, it was my backside for the larger injection in the morning and the upper arms for the smaller injection in the evening. Basal/bolus was backside for the basal so that it would work slowly and the arms again for most of the bolus. I only ever used my tummy for the bolus if my bg was a bit high which wasnt too often. Thankfully, I can insert infusion sets in my tummy ok because of that