T1D glossary

Closed loop (automated insulin delivery, AID)

Also called artificial pancreas, hybrid closed loop, looping.

A closed-loop system links a CGM, an insulin pump and an algorithm that raises or lowers insulin delivery based on CGM values. The FDA uses the names artificial pancreas, closed-loop and automated insulin delivery for the same idea. Hybrid systems give some insulin automatically, and the user still enters carbs at meals. Open-source systems such as Loop exist too. (FDA; NIDDK (NIH); ADA Standards of Care 2026, section 7)

Worked example

Overnight, glucose drifts from 140 to 190 mg/dL (7.8 to 10.5 mmol/L) and the system delivers more insulin; as it falls toward 90 mg/dL (5.0 mmol/L) it delivers less. At dinner, the user still enters the 50 g of carbs.

Related terms

• Continuous glucose monitor
• Basal insulin
• Bolus
• Insulin on board
• Carbs on board
• Nightscout

Sources, quoted

• FDA: “Sometimes an artificial pancreas device system is referred to as a "closed-loop" system, an "automated insulin delivery" system, or an "autonomous system for glycemic control."”
• NIDDK (NIH): “The program calculates how much insulin is needed and signals the insulin infusion pump when insulin needs to be delivered.”
• NIDDK (NIH): “Three devices make up an artificial pancreas system.”
• NIDDK (NIH): “An artificial pancreas automatically monitors your blood glucose level, calculates the amount of insulin you need at different points during the day, and delivers it.”
• NIDDK (NIH): “Most artificial pancreas systems require you to count and enter the amount of carbohydrates you consume at mealtime.”
• NIDDK (NIH): “These are called “hybrid” artificial pancreas systems, because some of the insulin is given automatically and some is given based on the information you enter.”
• ADA Standards of Care 2026, section 7: “Diabetes technology now also includes automated insulin delivery (AID) systems that use CGM-informed algorithms to modulate insulin delivery.”
• ADA Standards of Care 2026, section 7: “Loop, an open-source model predictive control algorithm, is implemented on iPhones as an app.”

Every quote above is checked against its source page before each update of this site; last checked 2026-10-06. The worked example is our own arithmetic. This page explains a term; it is not advice for a person's treatment.