Hi. As your Mum is on one injection per day this will be what's called Basal or background insulin which lasts 18 to 24 hours. The problem your Mum had overnight may have been a Hypo where the blood sugar goes too low i.e. below about 4 on the glucose meter. If this is the reason, and I'm guessing a bit, then the GPs advice to drop the dose just a little may well be the right advice. A low-carb diet is always a good approach for diabetics as it keeps blood sugar down and minimises blood sugar swings. Also as the weight comes down so does any insulin resistance due to fat cells and this helps stabilise blood sugar when taking insulin. If your Mum finds using her meter (I assume she has one?) that her blood sugar is regularly into the teens then come back for more guidance. Do come back anyway with any questions.