A Close Look of the Closed-Loop System

TL;DR: The close-loop system uses both CGM readings and an insulin pump to simulate very closely how the pancreas works.

For people without diabetes, the pancreas has a way of "detecting" glucose, and it secretes insulin when it "detects" that glucose is going too high. For people with diabetes, a technology that does virtually the same thing has emerged, known as the "close-loop" system or an artificial pancreas.

There are two parts of the close-loop system: the continuous glucose monitor (CGM), and the insulin pump. The CGM, much like the insulin pump, sticks a big needle into you, before retracting that and putting a much smaller needle into the incision. This much smaller needle has a sensor attached which can measure glucose levels in interstitial fluid, the fluid that surrounds cells and is generally a good indicator of blood glucose. Every few minutes or, with some CGMs, whenever the user desires, the CGM reads the glucose level and sends it to your phone or insulin pump. If the insulin pump receives the data, it may use the numbers and trends to determine how much "background" insulin to give - basically acting like long-acting insulin, but "personalized" to glucose data.

Today, there are several insulin pumps that have a closed-loop feature. They include the Omnipod 5 and the Tandem t:slim with Control IQ. Although they do offer background insulin "personalized" to your glucose data, they're not perfect because insulin takes time to act, quite unlike the insulin your body naturally generates. Simply relying on the background insulin given by these pumps guarantees poor glucose control since the insulin just isn't fast enough to keep your glucose in check! So although the close-loop system is a great way to improve your diabetes regimen, it's not a cure. Until a cure is found, it's important to keep counting carbs and giving appropriate amounts of insulin.