Two ways to unlock Pro: $9.99 a year, or $19.99 once — yours forever with Family Sharing.
SolGlow turns your time outside into the number that matters: vitamin D — measured in IU, not just minutes.
And it's automatic: your Apple Watch's daylight is credited to your estimate by itself — no logging, no GPS trail — and every number can show the exact math behind it.
From your Time in Daylight, skin type, outfit, age, and your location's sun angle, SolGlow estimates the vitamin D you actually made today — and warns you before you burn.
Every estimate comes from a named, peer-reviewed model — Holick, Heaney/Veith, Fitzpatrick, Spencer. No black boxes.
TODAY, AT A GLANCE
• Live UV index and your personal IU-per-minute rate
• One daily goal, tuned to your life stage — celebrated when you hit it
• Burn-safe time remaining for your skin type, with alerts before you burn
• Morning Light: catch the first light that anchors your energy and sleep
AUTOMATIC, AND YOU CAN SEE WHY (FREE)
• True-D: SolGlow corrects the UV Index for ozone — because sunburn UV isn't vitamin-D UV — and shows the cited step whenever it changes your number (Kazantzidis 2009)
• Vitamin D from your Apple Watch's Time in Daylight, credited automatically — no GPS trail, no manual logging, no tracking
• Tap "See how this was calculated" and every number shows its math — the model, your real inputs, the studies on screen (Holick 2007, Spencer 1971)
• Ask Siri "How much sun did I get in SolGlow?" — plus a Best Sun Window widget for StandBy, Lock Screen, and Home Screen
OWN THE WINTER
• Winter Mode: when your latitude's noon sun can't make vitamin D, SolGlow shows where yours is coming from — and counts down to the sun's return
• Free Winter Countdown widget and Apple Watch complication — it even works offline
• Streak Shield: only physics can excuse a missed day — winter freezes your streak instead of breaking it
• One-tap supplement check-in from a notification, widget, Siri, or your watch
• Log UV-lamp sessions against your lamp maker's own limits (Pro) — the overexposure warning is free
• Back up to your own iCloud, encrypted before upload if you choose — still no SolGlow servers, ever
SUN SESSIONS (PRO)
• Live Activity on your Lock Screen and Dynamic Island: live IU counter, burn-safe countdown
• Sunscreen reapply timer with an "I reapplied" restart right from the notification
• Editable history, streaks, goal rings, and a shareable weekly recap — plus the Apple Watch app and complications
PLAN AHEAD (PRO)
• 7-day UV forecast with your personal best-sun windows
• Annual sun plan: which months actually make vitamin D at your latitude
• Trip Planner: destination UV outlook plus a research-based sleep-and-light schedule to beat jet lag (timing guidance, not medical advice)
PRIVATE BY DESIGN
No account. No sign-up. No analytics. No ads. Your health data, profile, and location history never leave your device.
FREE TO TRY — THEN PICK YOUR PLAN
Every feature free for 14 days. Then choose your SolGlow Pro: $9.99 per year, auto-renewing until you cancel — or $19.99 once, yours forever with Family Sharing included. The free tier keeps today's tracking and all safety alerts, always.
Requires iPhone (iOS 17.2+). Apple Watch (watchOS 10+) strongly recommended — it's the source of automatic Time in Daylight tracking.
SolGlow estimates are educational, not medical advice. Always consult your clinician about vitamin D supplementation and blood testing.
SolGlow Pro Annual is an auto-renewing subscription: $9.99 per year, charged to your Apple ID at confirmation of purchase. It renews automatically unless cancelled at least 24 hours before the end of the current period. Manage or cancel it any time in your App Store account settings. SolGlow Pro Lifetime is a one-time purchase and never renews.
Privacy Policy: https://twisteddatastudios.com/privacy.html
Terms of Use: https://www.apple.com/legal/internet-services/itunes/dev/stdeula/
Update after first use: I sat out in the sun at “prime time” for 47 minutes. I turned on the tracker- it told me recording. When done, I turned it off and checked to see how much vitamin D I got and it logged zero. Useless. This needs a tutorial. Granted I just downloaded but right off the bat, I don’t see where to find best time to be in the sun, The beginning tracking button should be right at the top- big and in your face, not a little tiny pencil under start tracking that’s needs to be scrolled down to. Not sure if I’ll keep this…
Choose how you pay. SolGlow Pro now comes as a yearly plan alongside the one-time unlock.
A NEW WAY TO GET PRO
SolGlow Pro is now $9.99 per year, auto-renewing until you cancel — or stay with the one-time $19.99 unlock, yours forever with Family Sharing. Same features either way. If you already own the lifetime unlock, nothing changes for you: you keep it, and you'll never see a renewal prompt.
A NEW LOOK ON LAUNCH
A redesigned app icon and an animated opening built from SolGlow's own sun mark — the same mark now used across every widget, the Lock Screen, and the Apple Watch instead of a generic system symbol.
As always: no accounts, no analytics, no ads. Your data stays on your device (and your own iCloud only if you enable backup). Estimates are educational, not a diagnosis — always consult your clinician about vitamin D and blood testing.
Version 1.8
The developer, Michael Smith, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .
Data Not Linked to You
The following data may be collected but it is not linked to your identity:
Location
Privacy practices may vary, for example, based on the features you use or your age. Learn More
Accessibility
The developer has not yet indicated which accessibility features this app supports. Learn More
Information
Seller
Michael Smith
Size
8.6 MB
Category
Health & Fitness
Compatibility
Requires iOS 17.2 or later.
iPhone Requires iOS 17.2 or later.
iPad Requires iPadOS 17.2 or later.
Mac Requires macOS 14.2 or later and a Mac with Apple M1 chip or later.