# SolGlow: Vitamin D Tracker — Automatic Sunlight & UV Index > Automatic vitamin D estimation from sunlight exposure and UV index. (iPhone/iPad app by Michael Smith.) - Source: https://appshunter.io/ios/app/solglow-vitamin-d-tracker/id6763976252 (this page in markdown: same URL + `.md`) - Developer: [Michael Smith](https://appshunter.io/developer/1893971383) - Category: Health & Fitness - Price: Free with in-app purchases (on sale, was $3.99) - Rating: 3.00/5 from 2 App Store ratings · 1 written reviews indexed - Age rating: 12+ - Requires: iOS 17.2 · 9 MB - Languages: American English, German (Germany), Japanese, European Spanish - Released: 2026-05-05 - Data updated: 2026-09-09 - Monetization: freemium - User reviews in markdown: https://appshunter.io/ios/app/solglow-vitamin-d-tracker/id6763976252/reviews.md ## What is SolGlow? 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. TODAY, AT A GLANCE • Live UV index and your personal IU-per-minute rate • One daily goal, tuned to your life stage • Burn-safe time remaining for your skin type, with alerts before you burn • Log vitamin-D foods — presets or your own, in your units • 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 — 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 BRING YOUR HISTORY (FREE) • Import your whole Time in Daylight history from Apple Health in one tap — no account • Back up everything to one file and restore on a new phone SUN SESSIONS (PRO) • Direct Sun: a live burn budget for deliberate sun time — it only counts down, and says plainly when to get out • 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 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 plus a sleep-and-light schedule to beat jet lag (timing guidance, not medical advice) KNOW YOUR LEVEL (PRO) • 25(OH)D serum estimate with a 12-week projection • Cofactors: log magnesium, K2, B12, omega-3 • Personalized supplement guidance, blood-test reminders, and a doctor-ready PDF/CSV report PRIVATE BY DESIGN No account. No sign-up. No analytics. No ads. Your health data, profile, and location history never leave your device — the only network call fetches a UV forecast (coordinates only, no identifier). Optional backup goes to your own iCloud, never to us. 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. 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 purchase confirmation. It renews unless cancelled at least 24 hours before the period ends. Manage or cancel in your App Store settings. SolGlow Pro Lifetime is a one-time purchase that never renews. Privacy Policy: https://twisteddatastudios.com/privacy.html Terms of Use: https://www.apple.com/legal/internet-services/itunes/dev/stdeula/ ## Key features - Automatic vitamin D estimation - Live UV index and IU-per-minute rate - Burn-safe time remaining with alerts - Winter Mode for low-sun periods - Supplement check-in - 7-day UV forecast (Pro) - Trip Planner for jet lag (Pro) ## Pricing and in-app purchases Base price: Free. **One-time purchases** | Purchase | Price | Type | | --- | --- | --- | | SolGlow Pro | $7.99 | one-time | ## Recent user reviews (1 of 1) All indexed reviews: https://appshunter.io/ios/app/solglow-vitamin-d-tracker/id6763976252/reviews.md ### 1/5 — Needs a tutorial *2026-08-07* 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… ## Frequently asked questions about SolGlow ### What is SolGlow? SolGlow is a health and fitness app that automatically estimates your daily vitamin D intake based on sunlight exposure, skin type, age, and location. It provides real-time UV index, burn-safe time remaining, and integrates with your Apple Watch for effortless tracking. ### How does SolGlow estimate vitamin D? SolGlow uses named, peer-reviewed models like Holick and Heaney/Veith, factoring in your Time in Daylight (from Apple Watch), skin type, outfit, age, and your location's sun angle to estimate vitamin D produced in IU. ### Does SolGlow have ads? No, SolGlow is ad-free. The app is designed with privacy in mind and does not contain advertisements. ### What are the Pro features in SolGlow? SolGlow Pro offers advanced features like Live Activity on your Lock Screen, sunscreen reapply timers, editable history, a shareable weekly recap, the Apple Watch app, a 7-day UV forecast, an annual sun plan, and a Trip Planner for jet lag. ### How much does SolGlow Pro cost? SolGlow Pro is available as a subscription for $9.99 per year, auto-renewing until canceled, or as a one-time purchase for $19.99. All features are free for a 14-day trial period. ### What devices does SolGlow support? SolGlow is available on iPhone, iPad, and Apple Watch, with support for widgets on StandBy, Lock Screen, and Home Screen. ### How often is SolGlow updated? The latest version of SolGlow is 1.8, which was last updated on August 5, 2026. Updates typically occur to improve features and reliability. ### Is SolGlow suitable for children? SolGlow has an age rating of 12+, indicating it is appropriate for users aged 12 and older. It helps users manage sun exposure and vitamin D intake. ## Version history (last 5 releases) ### 1.9 — 2026-09-05 Direct Sun: for the days you're not just outside — you're out in it. DIRECT SUN (PRO) Start a session in Direct Sun mode and the headline number becomes your burn budget: the share of today's burn threshold you've spent, live on your Lock Screen and Dynamic Island. It never recommends more time and never estimates a tan — it only counts down, and tells you plainly when it's time to get out. Sunscreen (with the reapply timer) stretches the budget; nothing else does. YOUR BURN ALERTS GOT MORE HONEST (FREE, FOR EVERYONE) A sharp-eyed user in New Zealand — with a weather station on an all-day-sun deck — showed us a wrong cloud forecast could talk the app into "no burn risk" on a burning day. Fixed, at the physics level: burn math now refuses to believe clouds remove more than half of the clear-sky UV at your sun angle. Forecasts can be wrong; your burn alerts no longer inherit their optimism. ALSO NEW • Sky looks clear? Tell SolGlow, and for the next 30 or 60 minutes it uses true clear-sky UV instead of a cloudy forecast — labeled, with a countdown • Add your own vitamin-D foods (green-lipped mussels, anyone?) — and serving sizes now speak metric where you do • Raising your daily goal no longer erases history: past days keep the goal they were lived under, so met days stay met • Sun sessions now have an in-app status page, and past sessions can be reviewed and edited in History • "September Head-Start" is now Winter Head-Start — it always keyed off your latitude's seasons, and now its name works in both hemispheres • The serum projection now states its assumption: your current intake, held steady 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. ### 1.8 — 2026-08-05 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. ### 1.7 — 2026-07-16 The real number. SolGlow now corrects for what the sun actually does. TRUE-D: OZONE-CORRECTED VITAMIN D The UV Index measures sunburn, not vitamin D — and the two diverge whenever ozone is high or the sun is low. SolGlow now re-weights UV into true vitamin-D UV using total-column ozone and sun angle, with the studies named on screen (Kazantzidis 2009; CIE action spectrum). Your free estimates only ever get more honest — they are never inflated. Pro's hour-by-hour reconstruction runs the full physics. SEE THE OZONE STEP Tap "See how this was calculated" on any number: when ozone changed today's result, a new cited step shows exactly how much — "a high-UV day can still be a weak vitamin-D day," with the math on screen. If your numbers read slightly different than before, that's the correction working; a one-time note in the app explains it. NOW FULLY LOCALIZED SolGlow now speaks German, Spanish, and Japanese everywhere — the app, every widget, the Apple Watch app and complications, Siri answers, and even the system permission prompts. HONEST AT MIDNIGHT Widgets, the Watch complication, and Siri now roll over at midnight instead of showing yesterday's sun as today's. If a number is stale, SolGlow says "open to refresh" — it never presents old data as live. SMOOTHER FIRST RUN & PURCHASES • Permission requests now come one at a time, in context — never stacked on the welcome screen • The paywall shows real progress for Restore, explains Family Sharing "Ask to Buy" approvals, and remembers a pending approval across launches • Tap a locked widget and it now opens the unlock screen directly AND DOZENS OF POLISH FIXES Manual sun logging now works from an empty history; the serum estimate stays neutral until you anchor it with a blood test; clearer colors in bright light; a gentler day-one welcome; offline trip planning shows the physics fallback instead of an error. SolGlow Pro is $19.99 — one-time, no subscription, Family Sharing included. 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. ### 1.5 — 2026-07-10 Automatic, and you can see why — the biggest SolGlow update yet. SEE THE WORK Every vitamin D number now shows its math. Tap "See how this was calculated" and SolGlow re-runs the exact same model it used for your estimate — minutes in daylight, sun angle, skin exposed, skin type, age — as a plain-language step list with its sources named on screen. No black box. The explanation can never disagree with the number, because it comes from the real calculator. It's free. PASSIVE DAYLIGHT CREDIT SolGlow now quietly credits the vitamin D from your Apple Watch's Time in Daylight — automatically. No GPS trail, no manual logging, no tracking. A free Daylight Credit card shows today's IU and minutes outside, with a confidence rating so you always know how the number was made. Just live your day; the credit adds up. ASK SIRI "Hey Siri, how much sun did I get in SolGlow?" Three new read-only Siri and Shortcuts actions — Today's Sun, Vitamin D Level, and Best Sun Window. They read what SolGlow already computed and speak it back; they never change your data. The level answer is always spoken as a model estimate, not a blood test. BEST SUN WINDOW ON STANDBY A new free widget puts today's best sun window on your nightstand (StandBy), Lock Screen, and Home Screen — glanceable, no unlock required. TRIP PLANNER + JET-LAG (PRO) Traveling? Get a day-by-day sleep and light schedule to shift your body clock to local time faster, grounded in published circadian research, plus your destination's UV outlook. Timing guidance, not medical advice. BURN GUARDIAN A free trailing-3-day sunburn advisory that flags when your sun adds up across days — even when no single day crossed your limit. Estimated from your skin type and sun angle; advisory only, never a diagnosis. SESSION LIFEGUARD (PRO) Forgot to tap Done on a sun session? SolGlow now reconstructs it so your sunlight isn't lost, and saves it to history with an honest "estimated" label. ALSO IN THIS UPDATE • Serum Level drill-down (Pro): tap your estimate for a trajectory chart with a 12-week projection and a shaded optimal range. • Doctor Report now carries both your life-stage RDA and your personal daily goal, with separate PDF and CSV exports. • A custom daily goal now grades consistently everywhere — Today, Week Plan, streaks, and widget all agree. • Now available in Japanese, German, and Spanish. • Faster tab switches, and the Apple Watch refreshes the moment you open it. Founders pricing continues: SolGlow Pro is a one-time $14.99 — lifetime, no subscription. Going up soon. Buy once, keep it forever. As always: no accounts, no analytics, no ads, no tracking. Your health data stays on your device. Estimates are educational, not a diagnosis — always consult your clinician about vitamin D and blood testing. ### 1.4.1 — 2026-06-24 Switching to SolGlow? Now it's effortless — and your data is safer than ever. BRING YOUR HISTORY Coming from another sun tracker? SolGlow now imports your sunlight history straight from Apple Health — years of it, in one tap, no account. Start full, not empty. BACK UP EVERYTHING New Backup & Restore: save all your data — profile, history, sessions, blood-test baseline — to a single file you keep in Files or AirDrop to a new phone. Optional passphrase encryption. Still no servers, ever. SWITCHER SETUP A new "coming from another tracker?" path anchors your vitamin D to your last blood test and shows exactly what carried over. SET YOUR OWN GOAL Want a different daily target? You can now set your own vitamin D goal — in Profile, or by tapping the goal right on your Dashboard. (Also fixed: the larger widget now shows your vitamin D next to your goal, not your minutes outside.) - Various bug fixes and improvements. Founders pricing: SolGlow Pro is one-time $14.99 as of July 1st — lifetime, no subscription. Buy once, keep it forever. As always: no account, no analytics, no ads. Your data stays on your device. ## Apps similar to SolGlow | App | Rating | Price | Category | | --- | --- | --- | --- | | [D3-Sync: Sun & Supplements](https://appshunter.io/ios/app/d3-sync-sun-and-supplements/id6772340133) | — | Free | Health & Fitness | | [Nourix: FODMAP Diet & Scanner](https://appshunter.io/ios/app/nourix-fodmap-diet-and-scanner/id6775905596) | 5.0 (1) | Free | Health & Fitness | | [Self-Reliance Tips](https://appshunter.io/ios/app/self-reliance-tips/id6765832037) | — | Free | Health & Fitness | | [BIO: Circadian Rhythm & Sleep](https://appshunter.io/ios/app/bio-circadian-rhythm-and-sleep/id6763895181) | — | Free | Health & Fitness | | [Glow Flow: Tan Timer & UV](https://appshunter.io/ios/app/glow-flow-tan-timer-and-uv/id6758894681) | 5.0 (1) | Free | Health & Fitness | | [Vitamin D Window Widget](https://appshunter.io/ios/app/vitamin-d-window-widget/id6759223422) | 5.0 (2) | Free | Health & Fitness | ## More apps by Michael Smith - [CalmTide: Cortisol Tracker](https://appshunter.io/ios/app/calmtide-cortisol-tracker/id6776101012) All apps by Michael Smith: https://appshunter.io/developer/1893971383 ## Related topics [free vitamin d tracker](https://appshunter.io/ios/topics/free-vitamin-d-tracker) --- *Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-09-09.*