DOSBTS — a DOS amber terminal for your glucose

DOSBTS

DOS On Sugar · Built To See

A personal iOS app that reads Libre CGM sensors and shows them as a 1985-style amber phosphor terminal. I have Type 1 diabetes; this is the app I wanted, so I built it — and I wear it every day.

SIMULATOR 09:41

112 mg/dL →

IOB 1.4U · TIR 78% · 5 min ago

⚠ Personal, experimental project. Not a medical device, not FDA/CE-cleared, not medical advice. Never dose from software alone.

Standing on GlucoseDirect

DOSBTS is a fork of GlucoseDirect, Reimar Metzen's excellent open-source SwiftUI CGM app for Libre sensors. Everything that makes DOSBTS work — the sensor stack, the calibration, the architecture — is his, under MIT. I re-skinned it into a terminal and added the things I wanted on top.

If DOSBTS is useful to you, please support the upstream project first — the foundation this is built on is enormous.

Inherited from GlucoseDirect

◂Libre 1 / 2 / 3 + Bubble + LibreLinkUp sensor stack
◂Sensor calibration math
◂Nightscout upload
◂HealthKit + Apple Calendar export
◂The Redux-like app architecture
◂18-language localization

Added in DOSBTS

＋DOS amber CGA re-skin — CRT scanlines, phosphor widget
＋AI food logging — photo, text & barcode (Claude)
＋Guided hypo treatment — the "Rule of 15", lock-screen safe
＋Insulin-on-Board decay model + stacking warnings
＋Meal impact overlay + PersonalFood glycemic scores
＋Ratio Lab — ICR/ISF estimated from your own data
＋Clinic Report — PDF/CSV summary for appointments
＋Day/night alarm profiles + predictive low alarm
＋Daily digest with an AI insight
＋Event marker lane + tight-control streaks

Built to be read

GLUCOSE

Real-time, at a glance

A 24-hour amber chart with an insulin-on-board overlay, a predictive-low projection, and a stale-data guard so you never dose off a frozen reading.

FOOD

Log a meal three ways

Snap a photo, type it in plain language, or scan a barcode. The app estimates carbs with Claude and learns your foods from your corrections.

TREATMENT

It walks you through a low

A guided "Rule of 15" workflow: treat, a 15-minute countdown, recheck, and repeat if needed — driven from notifications, even on the lock screen.

RATIOS

Learn your own numbers

Ratio Lab estimates your insulin-to-carb ratio and correction factor from your own clean meals and corrections — every figure shipped with its sample size. Reference only, never a dose.

REPORTS

Clinic-ready in two taps

Export a clinician-readable PDF or CSV over 14 / 30 / 90 days — time-in-range, GMI, a 24-hour pattern and event counts — to share at your appointment.

FEEL

An instrument you own

Amber phosphor, monospace type, sharp corners, and exactly the right amount of CRT nostalgia. Diabetes UX that feels like a dedicated device, not a service you rent.

Ten months of amber

DOSBTS ships as TestFlight builds, changelog-first, in the open. The longer story — the decisions, the dead ends, the compound learnings — lives on the dmnc.tech devlog.

Feb 2026 Forked GlucoseDirect. First amber pixel on a black screen.

Builds 2–105 The re-skin, food logging, insulin-on-board, the treatment cycle, the daily digest.

Builds 106–128 Day/night alarms, meal-impact scoring, Ratio Lab, tight-control celebrations.

Builds 129–131 Empirical ISF from corrections, the Clinic Report export, cleaner chart markers.

Now Build 131 on TestFlight — and on my wrist every day.

Read the devlog →

Join the TestFlight

DOSBTS isn't on the App Store and never will be — it's a CGM app, and that's a regulated place I'm deliberately not going. It's open on TestFlight instead: install Apple's TestFlight app, tap the button, and you're in. You'll need a FreeStyle Libre 2 sensor to see live data.

The link opens Apple TestFlight. This site sets no cookies and collects nothing about you — beta enrolment is handled by Apple. See the privacy notice.