Frequently Asked Questions

Science-based answers about Vitamin D and the dminder app.

Troubleshooting (iOS)

The app shows a blank or black screen when I launch it (iOS) — what do I do?

Try these in order — most don't lose any data, and the last one is your guaranteed parachute:

  1. Force-quit and relaunch. Swipe up from the bottom of the screen and pause in the middle to bring up the App Switcher, then swipe D-Minder up off the top of the screen. Tap the icon to relaunch. About a third of black-screen reports clear with this alone.
  2. Restart your iPhone. Hold the side button + a volume button together until the “slide to power off” appears. Power off, wait 10 seconds, power back on. This clears OS-level state that occasionally traps the app.
  3. Update D-Minder from the App Store. Open the App Store, tap your profile photo in the top right, scroll down to “Available Updates,” and update D-Minder if it's listed. We ship fixes for the black-screen issue every release; you may already have a pending update.
  4. The parachute — delete and reinstall. If steps 1–3 don't work, this always recovers the app. Read the next FAQ entry below first if you're worried about losing your data.
    1. On the Home Screen, press and hold the D-Minder icon, then tap Remove App → Delete App.
    2. Open the App Store and search for “D-Minder”.
    3. Tap the cloud icon (or “Get”) to reinstall.
    4. Open the app. If you have iCloud Sync enabled (most users do), your sessions, lab results, and settings will restore automatically over the next minute or two.

Still stuck? Email support@ontometrics.com and tell us what your iOS version is, your iPhone model, and which steps you tried. The more specific, the faster we can help.

If I delete and reinstall (the parachute), will I lose my data?

Almost certainly no. D-Minder syncs every session, lab result, and setting to your iCloud account by default. When you reinstall and open the app while signed in to the same Apple ID, everything restores within a minute or two. To check that iCloud Sync is on:

  • Open Settings → tap your name at the top → iCloud → scroll to Apps Using iCloud → confirm D-Minder is on.
  • Or, in D-Minder before you delete: Profile → Settings → check that “Sync to iCloud” is enabled.

If you've ever turned iCloud Sync off, or you're not signed in to the same Apple ID on the new device, your local data won't restore automatically. In that case, before deleting:

  • Export to CSV: Profile → Data → Export to CSV. Email the file to yourself or save it to Files. After reinstalling, use Import from CSV to restore.

If the app won't even launch, you can't export — that's the trade-off of the parachute. iCloud Sync remains the safest option for nearly everyone.

Using the app

How do I start a sun session?

Tap the + button in the top right corner (iOS) or the orange + floating button at the bottom right (Android). This opens the action menu where you can start a Sun Session, log a Past Session, add Supplements, Food Doses, or UV Lamp Sessions. The + menu is your single entry point for all tracking in D-Minder.

How can it be that I cannot get Vitamin D whenever the sun is out?

Your body only generates D from UVB rays, which only enter the atmosphere when the sun is at least 30 degrees off the horizon. If you live in a place that is more than 35 degrees from the equator, that also means you will have parts of the year where there is no ability to make D at all, even at noon. The app tells you when you will next be able to make D whether it's an hour from now, or 3 months. On any given day, it will tell you the start and end times for that day (the time when the sun moves higher than 30 degrees and then lower again).

What is Solar Noon?

The time of the day that the sun reaches its maximum elevation angle: its highest point in the sky. This is the time of maximum Vitamin D production because the most UVB is entering the atmosphere (assuming the sun is greater than 30 degrees off the horizon that day).

Shouldn't I stay out of the sun in the middle of the day to avoid burning?

To get Vitamin D, you should go when you will make it at the highest rate, that way you will not have to stay out as long. If you burn easily, you also have a genetic advantage: you make Vitamin D up to 10x faster than people with darker skin. The app considers all these factors. And it will tell you what a safe amount of time to be out is and warn you when you have come up to that amount of time. Your body issues a warning of its own: before you burn, your skin will get pink and/or show patterning. If you abide by the warning times, that should never happen.

Is age a factor in how much D my body will make?

Yes. A person who is 50 needs 2x longer than a 20 year old to generate the same amount of D. The application applies this factor in computing the generation rate.

If I want to stay out longer, can I turn over to avoid burning?

Yes. When using the app, you can swipe the timer dial side-to-side and the application will ask if you are going to turn over. If you say yes, it will reset the warning timer.

How much D should I try to get per day?

The app lets you set your own target, which it will then use to show you how your performance has been vs. your goal. You set the level you want to get to and the app tells you how much you need to get. The RDA recommendation of 600 IUs was chosen because the goal is to be at least 20 ng/mL. Many other experts believe you should shoot for a level more like 40 or 50 ng/mL.

If I just got the results of a lab test, should I enter them in the app?

Yes. You can enter lab results every time you get them and the app will reset the continuous estimation to begin from that known point forward.

Won't sitting out in the sun age my skin more quickly?

UVA rays are the ones that cause photo aging, which is another reason to try to get out around Solar Noon (when the ratio of A to B is optimal). In a not totally surprising irony of nature: sun avoidance actually increases cancer risk. It's believed that this is the case because exposure prompts the body to generate burn defenses, so extensive avoidance makes burns more likely (also, Vitamin D prevents cancer). After years of telling people to avoid the sun, even dermatologists have backed off that position and are instead recommending safe sun exposure.

So you are saying I should never use sunscreen?

Not at all. One of the main uses of the app is to make it so you can go get your D and then either go inside, apply some sunscreen, or cover up.

How does the D level estimation work?

The app tracks all your sun sessions, supplement doses, and any lab results you enter. It uses pharmacokinetic modeling to estimate your current blood Vitamin D level (25-hydroxyvitamin D) over time. While it is true that everyone should attempt to achieve optimal levels, avoiding severely deficient ones is far more important, and continuous estimation helps you do that. Of course, periodic lab testing is still recommended to calibrate the model.

Can I import or export my session data?

Yes! D-Minder supports both CSV export and import on iOS and Android. You can export your entire session history as a CSV file to back up your data, move it between devices, or analyze it in a spreadsheet. To import, go to Profile > Data > Import from CSV (iOS) or Settings > Data > Import from CSV (Android) and select your file. The importer handles the standard D-Minder export format and automatically skips duplicate sessions.