To successfully master the art of dosing insulin, it is often helpful to start with a scientific mindset. No matter if you are using an insulin pump or manual injections, there are a few basic elements to successful treatment: basal insulin, meal boluses and correction boluses.
Basal insulin is either delivered by injections of long-acting insulin or by infusion of short-acting insulin by an insulin pump. The dose should be adjusted to cover the basic need of insulin of all cells in the body while resting. If the dose is too low, cells will not get enough energy. If the dose is too high, you may risk hypoglycemia.
Meal boluses are ideally meant to cover the macronutrients in a meal, mainly carbohydrates. The dose needed to cover a meal is depending on the amount of carbs, but also affected by large amounts of protein. The types of carbs in the meal (as measured by the glycemic index) determines when you need to take your insulin. If the meal contains sugar and the glycemic index is high, you may need to bolus ahead of time (pre-bolus). If the meal contains very complex carbs and fat that slows the uptake in your bowels, you may need to add a second bolus after an hour or two. Most people dose their meal boluses by either remembering how much insulin they need for a specific meal, or by assessing how many grams of carbohydrates are in the meal, and dividing that sum by their carb ratio. If your carb ratio is 10, that means you need 1 unit of insulin for 10 grams of carbs.
Since it is very difficult to exactly assess how much insulin to take, it is sometimes necessary to take extra short-acting insulin to correct for high blood sugar. To calculate how much insulin to take, you can use your correction factor. If your correction factor is 50 mg/dL, you would expect your blood glucose to drop by 50 mg/dL when you take 1 unit of insulin.