What Your Insulin Pump's Day-to-Day Patterns Can Tell You About Control

Modern hybrid closed-loop insulin pumps—like the MiniMed 780G—use algorithms to make automatic insulin adjustments throughout the day. The Automated Correction Index, or ACI, is a way to measure how much of your total insulin is being delivered automatically by the pump versus how much you're manually entering yourself.

Until now, researchers and clinicians mostly looked at the *average* ACI: the mean percentage of automated corrections over time. But a new study suggests that focusing only on that average might miss part of the story.

Researchers at multiple diabetes centers studied 330 people with Type 1 diabetes using the MiniMed 780G system. They looked not just at average ACI, but at how much the ACI *varied* from day to day over a 30-day period—a metric they call ACI-V%.

They found something unexpected: people with higher day-to-day variability in their ACI actually had better glucose control. Specifically, higher ACI-V% was linked to more time in the target glucose range (70–180 mg/dL) and less time running high. There was no meaningful connection between ACI-V% and time spent low, however.

The data also showed that ACI-V% and average ACI move in opposite directions: when the average automated correction amount was lower, the day-to-day variability tended to be higher.

The researchers identified a potential benchmark: patients whose ACI varied by 32.6% or more from day to day were more likely to achieve the common target of spending at least 70% of their time in range. This doesn't mean the threshold is a guarantee—the sensitivity and specificity of this cutoff were moderate—but it suggests a possible starting point for clinical conversations.

It's important to note that this is early, exploratory research. The threshold and its predictive strength will need to be confirmed in other studies before it could be used as a clinical tool.

If you use a hybrid closed-loop system, this research suggests that the day-to-day rhythm of your pump's behavior may reveal something useful about how well it's working for you—something different from just looking at average settings.

Your healthcare team may eventually use ACI-V% as part of understanding whether your pump algorithm is functioning optimally. For now, this finding offers a reminder that glucose management is never exactly the same from one day to the next—and that variability in how your pump responds isn't necessarily a problem. It might even be a sign that your system is adapting well to your changing needs.

If you're curious about whether this metric might apply to your own system, it's a great question to discuss with your diabetes care team.

Source: Diabetes research and clinical practice. Evidence type: PubMed indexed literature. Type1Cure is an information and intelligence hub, not a medical advice service. This article summarizes published research and does not provide diagnosis, treatment, or personal medical guidance. Always talk to your own care team before changing anything about your Type 1 diabetes management.