DexcomKit

A modern Swift package for connecting directly to a Dexcom G7 sensor and streaming glucose readings — designed to run alongside the official Dexcom app on the same phone.

⚠️ Not a medical device. DexcomKit is a community project, not affiliated with Dexcom. Never make treatment decisions based on data from this library — use the official Dexcom app for therapy.

How it works

The G7 accepts multiple simultaneous BLE connections and doesn't encrypt its real-time or backfill glucose streams. DexcomKit acts as a follower: the official Dexcom app (or a receiver) pairs with the sensor and runs the session; DexcomKit connects as a second listener — with no pairing, no bonding, and no pairing dialog — waits for the sensor to report an authenticated session, and decodes the readings.

The sensor advertises roughly every 5 minutes when it has a new reading, stays connected for a few seconds while it delivers data (including backfill for any gap while you were out of range), then disconnects itself. DexcomKit rides that cycle and rescans between readings.

The protocol implementation follows the reverse engineering done by LoopKit/G7SensorKit and xDrip4iOS — credit to those communities.

Installation

dependencies: [
    .package(url: "https://github.com/kylebshr/DexcomKit.git", from: "0.1.0")
]

Quick start

import DexcomKit

@MainActor
final class GlucoseStore {
    let monitor = G7SensorMonitor(
        configuration: G7Configuration(
            restoreIdentifier: "com.example.myapp.dexcomkit"
        )
    )

    func start() throws {
        try monitor.start()

        Task {
            for await reading in monitor.readings() {
                guard reading.isUsableForTreatment, let glucose = reading.glucose else { continue }
                print("\(glucose) mg/dL, \(reading.trendArrow?.rawValue ?? "steady"), at \(reading.date)")
            }
        }
    }
}

G7SensorMonitor is @Observable, so SwiftUI views can bind directly to monitor.connectionState, monitor.latestReading, and monitor.session — ideal for powering Live Activities. events() and readings() each return an independent stream per call, so any number of consumers (UI, Live Activity updater, storage, logging) can listen concurrently.

App configuration

In your app target:

• Info.plist: NSBluetoothAlwaysUsageDescription
• Info.plist: UIBackgroundModes including bluetooth-central
• Pass a stable restoreIdentifier so iOS relaunches your app for sensor events after termination (force-quit excepted — that's system behavior)
• Optional: UserDefaultsStore(suiteName:) with an App Group so widget and Live Activity extensions can read the followed sensor's session

The sensor must already be running a session with the official Dexcom app. With the default .automatic selection DexcomKit adopts the first sensor that proves it has an authenticated session; use .nameSuffix("8T") (the last two characters of the pairing code) to target a specific sensor.

Logging

Everything DexcomKit does is visible in the unified log under the subsystem com.kylebashour.DexcomKit:

log stream --predicate 'subsystem == "com.kylebashour.DexcomKit"' --level debug

Glucose values and sensor identifiers are .private by default; operational data (states, opcodes, timings) is .public. See the Diagnostics article in the documentation for the category map, a healthy-session log signature, and in-app log export via OSLogStore.

Documentation

The DocC catalog covers getting started, the full reverse-engineered G7 BLE protocol (UUIDs, opcodes, byte layouts), and diagnostics. Build it locally:

xcodebuild docbuild -scheme DexcomKit -destination 'generic/platform=iOS'

Development

The package is pure Swift 6 (strict concurrency) with CoreBluetooth hidden behind a protocol seam, so the entire state machine — parsing, adoption, backfill assembly, reconnect behavior — is unit-tested with scripted mocks and byte-exact fixtures. swift test runs natively on macOS; CI covers both macOS and the iOS simulator. State restoration and real advertisement cadence can only be validated on a physical device.

License

MIT — see LICENSE.