Need Help?
If you're experiencing issues with D3-Sync, have a feature request, or need help managing your subscription, please reach out to us.
FAQ
How is Vitamin D calculated?
The app uses the Holick synthesis model considering current UV index from Apple WeatherKit, the time you spend outdoors, your Fitzpatrick skin type, and how much of your skin is exposed.
Is passive tracking accurate?
Passive tracking relies on iOS significant location changes to detect when you step outside. It's an estimation. For the highest precision, we recommend using the manual Active Tracking timer.
How do I cancel my Pro subscription?
Subscriptions are managed directly by Apple. Go to Settings on your iPhone > [Your Name] > Subscriptions, tap D3-Sync, and select Cancel Subscription.