Say you think there should be a 50% split between basal and bolus insulin. That means someone should get about 20 units of basal insulin, and 20 units of bolus insulin, if their average total daily dosage (TDD) is 40U. However, that is a simplified rule that conflates three different variables. The body needs a certain amount of insulin throughout the day: that’s basal insulin. If the blood sugar is elevated for some reason (leaving out food for a minute), such as stress, exercise, sickness, hormones, etc. - then it needs to be corrected with the “correction factor” or insulin sensitivity factor (ISF). Finally, the third ratio is for food: carbohydrate or “carb” ratio, for how much one unit of insulin will cover how many grams of carbohydrates. If someone eats more carbohydrates one day, they will need more insulin... and you shouldn’t decrease the body’s baseline insulin needs (e.g. basal) to balance that ratio. The ratio therefore gets distorted.