Hi.As your father's leg is swollen and red,it could be Cellulitis
i.e. infection of subcutaneous layer and dermis of the skin .Because of the infection,the blood sugar levels are not coming to normal even after insulin
.In my experience,i prescribe broad spectrum antibiotic.If the symptoms are not relieved with Injectable antibiotics,Relaxing incisions
over the affected area are better which gives excellent results.Consult a Surgeon immediately as it may lead to septicaemia
, if delayed.All the best.