Integration of BGM/CGM into Automated Insulin Delivery (AID)

Integration of BGM/CGM into Automated Insulin Delivery (AID)

In an automated insulin delivery (AID) system, the continuous glucose monitor (CGM) drives the insulin pump, but the blood glucose meter (BGM) never fully leaves. What differs between systems is how a fingerstick reading gets in and what it changes once it's there. On the MiniMed 780G, a linked meter sends readings to the pump wirelessly, and the system uses each one to calibrate the sensor [1]. On the Omnipod 5 and the Tandem t:slim X2, you type the number in [2][3]. With the implanted Eversense 365 sensor, fingerstick calibrations are scheduled through the whole year of wear [4]. Here we cover the meter's side; our CGM hub covers the sensor side in Interoperability with Automated Insulin Delivery (AID).

Pairing: the 780G links to its own meter

The 780G has a matched meter. FDA lists the Accu-Chek Guide Link meter and Accu-Chek Guide test strips as part of the 780G system, and the meter sends blood glucose values to the pump over Bluetooth low energy [1]. Roche markets the Guide Link as exclusive to the 780G and the earlier MiniMed 770G [5]. A linked meter saves typing, but it also means that meter's strips feed straight into the sensor's calibration.

Ascensia sold its Contour Next Link and Contour Next Link 2.4 kits, packaged with Contour Next strips, as wireless blood glucose monitoring systems. As of October 2026, FDA's device identifier database lists every one of those kits as no longer in commercial distribution, the last with an end date of May 2026 [6].

Insulet's Omnipod 5 guide lists all FDA-cleared blood glucose meters as compatible, and you enter a reading by hand on the Enter BG screen or in the bolus calculator's glucose field [2]. Tandem's guide for the t:slim X2 running Control-IQ+ says calibration values go into the pump by hand, from any commercially available meter [3].

Calibration: when a strip reading changes the sensor

Whether a fingerstick changes what the sensor reports depends on the sensor. On the 780G with the Guardian 4 or Simplera Sync sensor, calibration isn't required, but the system is designed to use every meter reading, typed in or sent from the linked meter, to calibrate the sensor [1].

The Dexcom G7 and G7 15 Day sensors are factory calibrated, and users may enter an optional calibration [7]. Dexcom's guide says to enter it in the phone app or the receiver, not both [8]. A t:slim X2 user can also enter a G7 calibration on the pump [3], while the Omnipod 5 guide points Dexcom users to Dexcom's own instructions [2].

The FreeStyle Libre 3 Plus and 2 Plus sensors are factory calibrated and can't be calibrated by the user [9]. With either one, a meter reading is a check, never an adjustment.

The Eversense 365 sits at the other end. After a 24-hour warm-up it needs four fingerstick calibrations spaced 2 to 12 hours apart, then one a day through day 13 and one a week from day 14 [4]. During that first phase, if 8 hours pass without a calibration entry, the system stops displaying glucose data [4]. Sequel's twiist AID System works with the Eversense 365 [10].

What a bad strip reading does to a calibration

Here's what surprised us: Dexcom's own guide says calibrating "can make the G7 more accurate or less accurate compared to the lab result," because calibration pulls sensor readings toward the meter value [8]. Put plainly, the sensor takes on the meter's error. Tandem's guide says the accuracy of the meter used for calibration may affect sensor accuracy [3]. It goes on to warn that entering incorrect values, old values or sensor readings as calibrations could mean missing severe low or high glucose events [3]. It also says to calibrate with the meter you routinely use and not to switch meters mid-session, because meter and strip accuracy vary between brands [3].

On an AID system, sensor error doesn't stay on the screen. FDA's review of the 780G notes that a falsely high sensor reading could lead to over-delivery of insulin through automated dosing, and a falsely low one to under-delivery [1].

The calibration instructions read like a strip-handling checklist. Both guides say to wash and dry your hands first, use a fingertip sample because blood from other sites may be less accurate and not as timely, and enter the value within 5 minutes [3][8]. Tandem adds that strips should be stored properly and not expired [3]. Dexcom suggests waiting to calibrate while glucose is changing rapidly, since blood glucose changes a little before interstitial fluid glucose [8]. Even a meter built to FDA's 2020 guidance for over-the-counter use is expected to put 95% of results within 15% of a reference method, and 99% within 20% [11]. Every calibration carries that margin with it.

Typing a reading into a bolus calculator

Not every meter entry is a calibration. The Omnipod 5 SmartBolus Calculator suggests a bolus from the most recent sensor reading, or from a blood glucose reading when you use a fingerstick [12]. Insulet's guide says a reading typed straight into the calculator expires after 5 minutes, and one saved to history can be used for up to 10 minutes [2].

On the t:slim X2, CGM values fill the bolus calculator's glucose field automatically while Control-IQ+ is on. When readings don't match symptoms, Tandem's guide describes swapping in a meter value for that calculation [3]. One detail we didn't expect: a calibration entry on the t:slim X2 can double as a bolus input. With Control-IQ+ turned off, a calibration value above target brings up a correction bolus prompt; with it on, the pump simply returns to the CGM screen [3].

The iLet Bionic Pancreas goes furthest. FDA cleared its software to take manually entered meter values and keep dosing for a limited time when CGM input isn't available [13]. Our article on Closed-Loop Control Algorithms (Artificial Pancreas) walks through what each system does when the sensor stops.

The meter as backup

Dexcom's rule of thumb is "when in doubt, get your BG meter out." Its guide sends G7 users to the meter when there's no number or no trend arrow, or when readings don't match symptoms [8]. The 780G labeling treats sensor readings in Manual Mode as adjunctive, meaning confirmatory meter readings should be used for treatment decisions [1]. And the American Diabetes Association's 2026 Standards of Care say people who use a CGM must also have access to blood glucose monitoring [14].

Put together, strip use tracks the sensor more than the pump. A Libre 3 Plus wearer uses strips only for checks and backup. A G7 wearer can add optional calibrations, a 780G user calibrates with every reading entered, and an Eversense 365 user calibrates on a schedule. How many strips to keep on hand, and when to trust a fingerstick over the sensor, are decisions to make with your care team.