Diabetic dog

[Sammymac]

Hi everyone, my lab cross collie who is only 22 months old was diagnosed with diabetis about a month ago. I just wondered if anyone else has experience of this illness with their dogs. He was started on insulin injections once a day but that didnt stabalize him so he is now on 10units twice a day but what im finding difficult is the timing. He has food in the morning at 7am and then usually after his afternoon/evening walk which is about 5.30 to 6pm but the vet said his insulin should be given at 12 hr intervals after food, and im finding it very difficult to not feed him until 7pm - does anyone know if there is any leway in the times ie how long after food is safe to give the injection?