Your health data belongs to you.

This policy explains what information the Sustain app ("Sustain," "we," "the app") collects, how it's used, and what choices you have. Sustain is a personal medication and nutrition tracker for people using GLP-1 medications, built around one principle: your health data belongs to you, not to us.

The short version

Sustain requires a free account, created with Sign in with Apple or Continue with Google, and backs up your health data, dose logs, weight, protein intake, and side-effect notes, to your own account so it's available if you switch phones or reinstall. We don't sell or share it with advertisers, we don't use it to train any AI model, and only you can ever access your own data. Several optional AI features (described below) send limited data to our AI provider only when you actively use them.

Information we collect

Account information. Sustain requires a free account, created with either Sign in with Apple or Continue with Google, so your data can be backed up and made available if you switch phones or reinstall the app. This means we receive an email address (your real one, or, if you choose Apple's "Hide My Email" option, a private relay address that forwards to it) and a unique account identifier. Both are used only to authenticate you and keep your data linked to your own account, never for marketing, and never shared with anyone else. If you sign in with Google, we do not read or store your name or profile photo, only the email address and account identifier Google's sign-in provides. Signing in with a different provider than you used before creates a separate account, since Apple and Google identities aren't linked automatically; Settings → Account & Sync → Sign-in methods lets you link both to one account if you'd like either to work.

Health and medication data you enter. Medication name, dose amounts and dates, injection site, titration plan, weight entries, protein intake, and side-effect logs. You control all of this, nothing is collected unless you type it in or (for weight/protein) sync it from Apple Health.

Apple Health data. If you grant permission, Sustain reads and writes your body weight and dietary protein entries to Apple Health, so the two stay in sync and you don't have to log the same thing twice. This data is exchanged directly between the app and Apple's HealthKit framework on your device, it does not pass through any server we operate.

Photos, only when you use the AI photo-estimate feature. If you choose to snap or select a photo to estimate a meal's protein content, that image is sent to our AI provider (Anthropic, maker of the Claude models) solely to generate the estimate. The photo isn't stored by Sustain after the estimate is returned, and per Anthropic's own API terms, data submitted through their API isn't used to train their models. See Anthropic's privacy policy at anthropic.com/privacy for how they handle data submitted to their API.

Photos, only when you use lab result import. If you choose to photograph a lab or bloodwork report, that image is sent to our AI provider (Anthropic) solely to transcribe the printed values (test name, number, unit) so you can review and save them. Sustain does not interpret, flag, or evaluate any value — it transcribes what the report says, nothing more. The photo isn't stored by Sustain after the values are extracted, and the same no-training terms described above apply. Progress photos, a separate feature, are stored on your device only and are never sent anywhere — they aren't part of this.

Weekly AI summary data, only when you use that feature. If you use the optional "your week" AI recap, a small set of already-aggregated numbers (your dose adherence, average protein intake, and weight trend for the past 7 days, not raw logs) is sent to our AI provider to generate the written summary. The same no-training terms apply.

Chat messages, only when you use the AI chat coach. If you ask the chat coach a question, your typed question and that same weekly summary of your dose, protein, and weight figures are sent to our AI provider to generate a response. Nothing is saved after the conversation ends; Sustain does not keep a chat history.

Photos, only when you use the AI body scan. If you use the optional body-fat estimate, the two photos you take (front and side) are sent to our AI provider to generate the estimate, then discarded, the same no-storage handling as the other AI photo features above.

AI feature usage. So we can tell whether the AI features above are actually useful to subscribers over time, we record which of them you've used and when, and share that (tied to your subscriber account) with RevenueCat, our subscription-billing provider. This is never the content of anything you asked or logged, just which feature and when. It's never shared with advertisers or used to track you across other apps or websites.

App usage analytics. We use TelemetryDeck, a privacy-focused analytics provider, to understand how people use Sustain at a basic level: which onboarding steps are reached, whether a session was opened, which screen led to a paywall being shown, and whether an AI feature attempt succeeded or was blocked. TelemetryDeck doesn't use advertising identifiers and doesn't need Apple's App Tracking Transparency permission, because it isn't used for tracking. Your account identifier is hashed on your device before it's sent, and hashed and salted again when it arrives, so the value TelemetryDeck actually stores can't be reversed back to your account. We never send message content, photos, health values, medication names, weight, or dose amounts to TelemetryDeck, only which screen or feature was involved. See TelemetryDeck's own privacy documentation at https://telemetrydeck.com/privacy for how they handle this data.

Basic device and diagnostic information. Standard crash and performance diagnostics collected automatically by the operating system (not by us directly) if you've opted into sharing this with app developers in your iOS settings.

What we don't collect

We don't collect your name, precise location, or any advertising identifiers. We don't use tracking technologies to follow you across other apps or websites, and Sustain doesn't show ads and never will.

How your data is stored

Your logged data (doses, weight, protein, side effects) is stored on your device and synced to your Sustain account, so it's backed up and available again if you switch phones, reinstall the app, or sign in on a new device. It's stored on our infrastructure provider's servers (Supabase) and protected with row-level security, so only your own signed-in account can ever read or write your data. We don't sell it, share it with third parties, or use it for anything beyond providing Sustain's own features to you.

You can permanently delete your account and all of the data linked to it at any time, from within the app, at Settings → Account & Sync → Delete account. This actually deletes the underlying account and its data, not a deactivation you could later undo.

Subscriptions

Sustain+ is an optional subscription that unlocks full history, the AI features, and a few other conveniences. Subscription purchases are handled by Apple's App Store billing system, Sustain does not receive or store your payment information; that relationship is between you and Apple, governed by Apple's own privacy policy.

Your choices

You can decline HealthKit permission at any time and Sustain will simply rely on manual entry. You can avoid the AI features entirely and use Sustain purely for manual logging, which is always free. Because your data is backed up to your account, deleting the app from your phone does not delete it. To permanently delete your data, delete your account instead, from within the app at Settings → Account & Sync → Delete account. If you'd like a copy of what limited information we do process (e.g., logs related to a specific support request), contact us at the email below.

Children's privacy

Sustain is not directed at children and we do not knowingly collect information from anyone under 13 (or the relevant minimum age in your region). If you believe a child has provided us information, contact us and we'll address it.

Changes to this policy

If we change what data Sustain collects or how it's used, we'll update this page and, for material changes, make that clear within the app itself.

Contact us

Questions about this policy or your data can be sent to support@hearthlyapps.com.