Hi. 2 to 3 units doesn't seem to be way off for a 3-year old and they will be taking it in steps. I only have 9 units a day of long-acting at 60Kg. I suspect your wife may be a bit higher in weight and need more insulin due to some insulin resistance? I'm only guessing but it might explain some of the difference. Daily insulin units are normally related to body weight. Although 19mmol is much higher than it should be, you would normally need to be into the 20s to start being at risk of ketoacidosis. I was sometimes in the 20s when just on tablets. I suspect your son's blood sugar levels will drop quite well over the next few days, so don't panic. I guess you will be needing to ask the nurse about short-acting insulin being added if it hasn't been already, carb counting etc. Your wife's experience will help a great deal.