You pre-program your insulin pump to deliver a tiny amount of insulin every few minutes in a cycle of 24 hours. This is known as a basal rate pattern.

The basal rate replaces the insulin that your body is not producing or producing enough of naturally.  The basal rate Provides a low, continuous level of insulin that controls glucose overnight and in between meals.  The rate is programmed as unit(s) per hour. You can program different patterns to meet different needs. Some examples that might prompt additional programming are: weekend or shift work, exercise, hormonal fluctuations, or travel.  In a basic pump the basal infusion occurs automatically; it just keeps delivering insulin in the pre-programmed pattern until you decide to change the rate.   In systems integrated with continuous glucose monitors (CGMs), the basal rate may be adjusted automatically by the pump according to the glucose trends.

Bolus insulin

You can also pre-program your insulin pump with the bolus settings, including the insulin to carbohydrate ratios, bolus infusion profiles, and insulin sensitivity factor, or correction factor.

Insulin-to-carbohydrate ratio is programmed as 1 unit of insulin per number of carbohydrate grams. This means that 1 unit of insulin will dispose of so many grams of carbohydrate. Multiple insulin-to-carbohydrate ratios may be set for different meals – breakfast, lunch, dinner, snacks, etc. For example, if 1 unit of insulin disposes of 10 grams of carbohydrates, it is expressed as the ratio 1:10 grams of carbohydrate.

On certain pumps settings also can be pre-set to deliver an extended bolus, insulin for food that is divided and delivered over a specified period of time. This only availabel while in manual mode and not option while a closed loop system is active.  The proportion of the immediate versus prolonged delivery, the overall time duration of the delivery, and the insulin to carbohydrate ratio can be varied depending on fat content and other digestion considerations.  Check with your pump manufacturer for specifics.

Insulin sensitivity factor, or ISF, refers to how much or how many points (mg/dl) the blood sugar will drop in response to one unit of insulin. It is also known as a high blood sugar correction, and is set as one unit of insulin to lower a specific amount of glucose (in mg/dl). Different ISFs can be pre-programmed for different times of the day. A common example would be 1:50. This means that 1 unit of insulin will drop blood sugars 50 points.

Unlike the basal insulin infusion, bolus infusions are NOT necessarily automatic.  In all pumps, you need to announce carbohydrates when eating.  In a closed loop system, correction boluses may be automated as well as deliverable by the pump user.

The insulin pump or continuous subcutaneous insulin infusion device (CSII)  continuously administers rapid acting insulin into the fatty tissue beneath the skin. The insulin pump is especially suited to covering different patterns of insulin resistance or sensitivity throughout the day. The pump may also have multiple methods to deliver a bolus such as: standard, dual wave, and extended boluses.  This is dependent upon the make and version of the insulin pump, check for features specific to your make and version pump.

Target blood glucose

You can program your pump with your individual target or desired blood glucose level usually 100-150 mg/dl depending on which pump you  are using.

Insulin on Board (IOB)

What is it?

IOB is the piece of program that keeps track of how long a bolus of insulin is working, so you can adjust your next insulin bolus to prevent overlapping insulin effect from multiple boluses.  You set your IOB for a certain amount of time or an indicated by the type of algorithm that is active.  Depending upon the dose of rapid-acting insulin (analog insulin), it is usually set for 3-5 hours.  Your provider will help determine what might be suggested for you.

What are the benefits of the IOB feature?

• Helps prevent “stacking” insulin, or excessive correction of a high glucose, that can result in hypoglycemia
• Helps avoid giving too little insulin in treating high glucose for fear of hypoglycemia