SolGlow: Vitamin D Tracker

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

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, restore on a new phone, and anchor your estimate to your last blood test

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)

KNOW YOUR LEVEL (PRO)
• 25(OH)D serum estimate with a 12-week projection
• Cofactors: log magnesium, K2, B12, omega-3 — the nutrients that activate vitamin D
• 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 iCloud backup goes to your own iCloud, never to us.

FREE TO TRY, YOURS FOREVER
Every feature free for 14 days. Then unlock SolGlow Pro with a one-time $19.99 purchase — no subscription, ever. 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.