Another risk from repeated sub cutaneous (sc) injections (i.e any injection into the fatty tissue under the skin which does not go into either a vein - iv - or muscle - im) are lumps of scar tissue which can accumulate with time. These can be painful and disfiguring. As far as I am aware, they only really occur in cases where you are being injected more than once a day, every day but it is best to be careful. I have them all over my thighs and stomach (not so much in the arms) and have been told that the only way to get rid of them is to not inject in that location for at least 6 months (practically impossible for me as a diabetic...) so that the damaged tissue can be repaired. You are more likely to get them if you are clumsy with the needle.

One sign that you have this is when a particular, favoured location for injecting into becomes less painful to inject into and there is a definte lump under the skin. Though, on the breast, you have to be careful you are not mistaking this for something more sinister (get any lump checked out by a doctor).