Direct-to-Watch CGM Architectures

Direct-to-Watch CGM Architectures

A direct-to-watch CGM doesn't put a glucose sensor inside the watch. The sensor on the skin still does the measuring; in direct-to-watch mode it sends readings over Bluetooth straight to a smartwatch, so the phone can stay behind [1]. As of October 2026, the only version we could confirm is Dexcom's Direct to Watch for the Dexcom G7 and Dexcom G7 15 Day sensors, and Dexcom says Apple Watch is the only smartwatch that supports it [1] [2]. The phone hasn't left the system, though. It still pairs every new sensor and steps in whenever the direct link drops [3].

Three ways glucose reaches a watch

When we sorted the watch features we could find, they fell into three designs. Only two of them involve an FDA-authorized sensor.

• Sensor to watch. The CGM sensor keeps its own Bluetooth connection with the watch, which is how Dexcom describes Direct to Watch [1].
• Phone relayed. The sensor talks to a phone app, and the phone forwards readings to a watch app. In Dexcom's version, Standard Smartwatch mode, the phone has to stay within 20 feet for readings to keep reaching the wrist [4].
• Watch-based sensing. The watch or ring claims to measure glucose itself, with nothing piercing the skin. The FDA warned in February 2024 that it has not authorized any smartwatch or smart ring that measures or estimates blood glucose on its own [5].

The first two designs share a sensor and its numbers. Only the data's path differs, and with it what breaks when a link goes missing.

How Dexcom's Direct to Watch works

Here's the detail that made the design click for us. A Dexcom G7 sensor has three Bluetooth channels: one for the smartphone (which feeds the Clarity and Follow apps), one for a smartwatch, and one shared by a Dexcom receiver or a connected automated insulin delivery (AID) system. Dexcom says these run at the same time and independently [6]. Direct to Watch simply puts the smartwatch channel to work.

The hardware list is narrow. As of October 2026, Dexcom lists Apple Watch Series 6 through Series 11, the second- and third-generation Apple Watch SE, and the Apple Watch Ultra models through Ultra 3, all running watchOS 10 or later [7]. Setup also needs an iPhone on iOS 17 or later [8] and Dexcom G7 app version 2.2.1 or later [9]. The watch doesn't need a cellular plan, because the sensor link is Bluetooth [9].

On the wrist, Direct to Watch shows the current reading, the trend arrow, the trend graph and alerts. Tap the graph and it shows the past 1, 3 or 6 hours [10].

What still runs through the phone

We expected "direct" to mean the phone was optional. Dexcom's own support pages show it isn't, for at least four jobs.

• Pairing. Each new G7 sensor has to be paired with the watch through a compatible phone, and a sensor pairs with only one smartwatch [3].
• Settings. The watch copies its settings from the phone app, so changes carry over only when the watch app is opened with the phone nearby [3].
• Fallback. An orange phone icon beside the reading means Direct to Watch is temporarily not working and the watch is copying data from the phone instead [3]. A gray phone icon means Standard Smartwatch mode [4].
• Sharing. Since the G7 app's 2.7 release, the watch can send readings to Followers, but only over Wi-Fi, never cellular. With no Wi-Fi and no phone in range, Followers see nothing until a connection returns, then the missed data fills in [11]. Real-time data to partner apps such as Sugarmate stops while the phone is left behind [12].

Water is a separate limit. Readings may not arrive until the wearer gets out; afterward, the watch's graph can fill in up to 6 hours of missed readings, against up to 24 hours on the phone app or receiver [13].

Phone-relayed watch displays

The older design keeps the phone in the middle. Dexcom says that before Direct to Watch, an Apple Watch depended on the iPhone for glucose values and had to stay within Bluetooth range of it [14]. The Dexcom G6, which Dexcom is phasing out in favor of its G7 sensors and stopped manufacturing after July 1, 2026, never got Direct to Watch [15] [16]. Its Android watch face, for example, shows readings only while glucose data is showing in the G6 Android phone app [17].

Abbott's Libre app for Watch is phone-relayed too. As of October 2026, Abbott says it's available only for Apple Watch, and the Libre phone app behind it works with the FreeStyle Libre 2 Plus and Libre 3 Plus sensors [18]. The fine print spells out the architecture: glucose reaches the watch only when the phone is in range of both the sensor and the watch, and watch notifications are mirrored from the phone [18].

Pumps, AID and the watch

Because the watch has its own channel on a G7 sensor, Dexcom says a Direct to Watch user can stay connected to an AID system at the same time [6]. The catch is that the receiver and the AID system share one channel, so the sensor connects to one or the other [6]. The watch only displays readings; pump and AID settings are a decision for you and your care team. Our article on interoperability with automated insulin delivery covers how CGMs and pumps connect.

Watch-based sensing is not authorized

The third design is what many people picture when they hear "glucose on a watch," and no authorized product does it. The FDA's 2024 warning covers any smartwatch or smart ring, regardless of brand, that claims to measure blood glucose without piercing the skin; the agency says these devices don't directly test blood glucose [5]. Its concern is concrete: inaccurate readings can lead to errors such as taking the wrong dose of insulin [5]. The same warning draws the line this article does, separating those devices from watch apps that display data from an FDA-authorized CGM [5]. Our article on non-invasive [glucose monitoring technologies](/continuous-glucose-monitoring/non-invasive-glucose-monitoring-technologies/) covers the research.

What the watch doesn't change

Accuracy belongs to the sensor, not the screen, and so does the evidence. In the DIAMOND randomized trial (JAMA, 2017), 158 adults with type 1 diabetes on multiple daily insulin injections were assigned to CGM or usual care, and the CGM group's A1C fell more over 24 weeks [19]. It tested CGM use, not where the reading was displayed.

Both manufacturers keep the fingerstick meter in the picture. Dexcom's watch pages say a blood glucose meter should be used for treatment decisions when readings don't match symptoms or expectations [4], and Abbott says its smartwatch app shouldn't be used to make treatment decisions at all [18]. How to act on any reading is a decision for your care team.

As of October 2026, the only true sensor-to-watch link we could confirm covers one CGM family and one watch brand. It still leans on the phone for pairing, settings, and sharing away from Wi-Fi, and Dexcom says Apple Watch remains the only smartwatch it supports [2].