There are frequent fluctuations in the blood sugar level, making it difficult to determine the quantum of insulin to be given to my wife. what should i do?

Food: What she eats and how much cause the variation in blood sugar. We don't eat the same thing in the same amount every time. Thus the need to check blood sugar regularly.

Several options: The biggest determinant of how blood sugar responds to meals is the amount of carbohydrate the food and the amount of meal Insulin (as NovoLog or humalog). Many patients will calculate the dose of mealtime Insulin using a ration (that is individual for them) of how many grams of carbohydrate a unit of Insulin may "cover.".

Need carb counting: I agree with both answers given so far. Many people tend to adjust the Insulin dose based on what their sugar is at the time they take insulin. However, the much more important factor is what is being eaten. Adjusting the dose of short acting Insulin based on carb intake is far more important than adjusting based on the sugar reading.