Vitamin D From the Sun: A Daily Estimate
Apple Watch counts your minutes in daylight. Metrya combines them with the UV index, your skin type, D3 in your stack and food apps for a rough daily estimate of vitamin D. An estimate, not a blood level.
One number for today
The Light page shows a small three-part ring with one row per source. The Today Daylight card gets one line with the same number.
The sun
Apple Watch daylight minutes, weighted by the UV index at that minute, your skin type and how much skin was out.
Your stack
D3 doses you log in Metrya's Stack, when the dose is in IU or mcg.
Food apps
Dietary vitamin D that other apps write to Apple Health.
Careful on purpose
Real vitamin D production varies a lot between people, places and days. Metrya stays on the low side and says so.
Only UV 3 or more counts
On low-sun days the sun part is 0, and the app says "The sun is too low today for vitamin D".
A quarter of daylight
The watch cannot tell sun from shade or a bright window, so Metrya counts a quarter of your daylight minutes.
Your target
Starts at 600 IU (800 IU over 70). Change it any time.
Skin and sunscreen
Skin type, the skin you usually have out and sunscreen, set once.
Daylight and vitamin D are different things
A D3 capsule adds vitamin D but no daylight. An hour outside in October adds daylight but almost no vitamin D. Metrya never says one goal is met because the other is.
Set it up once
Wear your Apple Watch
It records Time in Daylight and writes it to Apple Health.
Turn on a weather location
A coarse location gives Metrya the UV index for your area.
Answer four questions
Skin type, skin out of doors, sunscreen and your daily target.
Your health data stays on your iPhone
The estimate is calculated on your iPhone. Only a coarse location, rounded to about 1 km, goes to the weather service for the UV index. No health data goes with it, and there is no account.
Is this my vitamin D level?
No. It is a rough estimate of what today may have added. Only a blood test shows your vitamin D status.
Why 0 IU after a sunny walk?
When the UV index stays under 3 all day, the sun part is 0. This is common in autumn and winter.
Is it free?
The sun ring and sun path are free. The vitamin D estimate is Pro. Pro is $14.99 a year or $19.99 once for lifetime.
See what today's sun added.
Download Metrya, allow Apple Health and turn on a weather location.