SolGlow turns Apple Watch's Time in Daylight, your location, and your skin type into a real estimate of the vitamin D you produced today — supplements, food, and sun, all in one place. Nothing leaves your device but a forecast lookup.
SolGlow combines what your Apple Watch already measures (Time in Daylight) with the physics of where you are and the biology of your skin — and folds in your supplements and food. It's an estimate, but a transparent one: every input is shown.
Reads the daylight your Watch already records. SolGlow never modifies it — it only reads.
Computes your sun's elevation and the local UV factor for accurate vitamin-D synthesis windows.
Skin-type-aware synthesis and burn-time calculations — Type I through VI all dialed in.
Forecasted UV combined with your time outside warns you before your skin's threshold is crossed.
A calendar of your actual sun, supplement, and dietary vitamin D — with location-aware attribution for travel days.
Today's IU, sun minutes, and daily-goal progress at a glance — refreshed in the background.
Glanceable Progress, Serum, and Forecast cards on the wrist. Pulls Time in Daylight straight from watchOS.
Heaney/Veith dose-response converts your daily IU into projected 25(OH)D in ng/mL.
USDA FoodData Central built in. Salmon, eggs, fortified milk — all rolled into your daily total.
SolGlow makes exactly one network call: a UV forecast lookup to Open-Meteo with just a latitude and longitude — no name, no account, no device ID. Apple Health data, your profile, your food log, your location history — all of it stays on your iPhone in iOS app-private storage, pruned automatically after 60 days.
Free download with a 14-day Pro preview. After that, unlock SolGlow Pro forever for a one-time $7.99 — Family Sharing included. No subscription. No ads. Requires iOS 17.2 or later. Apple Watch (watchOS 10+) recommended for the most accurate Time-in-Daylight data.
Now on version 1.4 “Celebrate the Sun.” See the full update history →