Does Sunscreen Block Vitamin D?

The short version for skimmers...

• Daily sunscreen does lower your vitamin D a little. The best trial so far puts it at about 2 ng/mL. That's a small, fixable gap.
• Your skin stops making vitamin D after a while, so staying out longer doesn't get you more. It only gets you more UV.
• The light that makes vitamin D is the same light that burns you. There isn't a time of day that gives you one without the other.
• In Connecticut, and anywhere else above about 35 degrees north, the winter sun makes almost no vitamin D, with or without sunscreen.
• So: protect your skin, and get your vitamin D from a supplement. A year of D3 costs less than a tube of sunscreen.

It's the end of August 2010 and Annmarie and I are living out of an RV, somewhere between Palm Springs and Phoenix, and it gets hotter every mile. We've spent the last few years outside about as much as two people can — beaches, hikes, runs, afternoons in whatever park we're parked next to. Annmarie, for every hour I'm in the sun, is out there for two, in a bathing suit.

So when we get our vitamin D tested, I'm not worried. I'm curious how high it'll be.

Mine comes back at 23 ng/mL. Annmarie's is 22. The lab's normal range starts at 32.

I write about it in our newsletter the next day, because I figure if two people who basically live outdoors are low, a lot of other people are too. A bunch of readers write back with the same story. A few more write back angry. The sun makes vitamin D, they tell me. Everybody knows that.

They weren't wrong. The sun does make vitamin D. It just hadn't made enough of it in us.

A few others had a theory for us. They'd read that washing with soap strips away the skin oils your body needs to make vitamin D, so maybe that was our problem. I'd read the same article, agreed with it, and even made a video about it. I also hadn't used soap — outside of the obvious places — in over three years. I was still at 23. (For the record, that theory doesn't hold up either. Your skin makes vitamin D in its living layers, not in the oil on top, and a shower doesn't wash it away.)

So many theories, so many thoughts, but what is true? That was sixteen years ago and there are plenty in the health community still arguing back and forth.

I know for me, I've solved it. I've got my levels over 50 with a supplement and hadn't thought about it since.

That was until we started making sunscreen and the questions started bubbling up again.

So I figured now is a good time to revisit it.

How does your body make vitamin D from the sun?

Your skin carries a form of cholesterol that turns into vitamin D3 when UVB light hits it. UVB is the burning part of sunlight. The reaction is quick. A fair-skinned person at midday in summer, with arms and legs bare, can make the equivalent of 10,000 to 25,000 IU in under ten minutes — more than most supplement bottles hold in a single capsule.⁷

It also shuts itself off. Once your skin has made a certain amount, more sun breaks the extra back down into inactive compounds.⁶ You can't overdose on vitamin D from the sun, which is good. It also means a two-hour beach day doesn't bank you twelve times what a ten-minute walk does. After the first stretch, you're collecting UV damage and very little else.

Then there's where you live. Above roughly 35 degrees north — draw a line through Atlanta and look at everything above it — the winter sun comes in at too low an angle and the atmosphere filters out the UVB you need. Researchers measured this in Boston in the late '80s: from November through February, skin there made essentially no vitamin D at all.⁵ We live in Newtown, Connecticut, which sits at about 41 degrees, close to Boston's latitude. For four months a year, my sunscreen has nothing to do with my vitamin D. The sun just isn't being generous.

Skin tone matters too. Melanin is a built-in sunscreen — one study found about five times as much UV gets through white skin as it does darker skin⁸ — and that's legit protection. Darker skin burns less and starts with a lower baseline risk of skin cancer. But the pigment that soaks up the burning rays also slows vitamin D production.⁹ A very fair-skinned person might make a day's worth in about fifteen minutes of summer sun; someone with darker skin can need anywhere from half an hour to a few hours for the same amount. The size of that gap is debated — a 2016 systematic review found the pigment effect smaller and less consistent than the older studies suggested¹⁰ — but the direction isn't in question. Put darker skin at a northern latitude in January and deficiency becomes common, and that's where a supplement does the most good.

For me, on the paler side, I burn easily. I've never been the guy who could stay out long enough to make his vitamin D without paying for it. So supplementation has always been my go to.

Does sunscreen block vitamin D?

Yes, a little.

On paper it should block a lot. In the lab, sunscreen applied at the tested thickness stops nearly all the UVB that makes vitamin D. In real life almost nobody applies it that way — most people use a quarter to half of the tested amount, miss patches, and don't reapply. That's why, for years, study after study found everyday sunscreen use made little measurable difference to people's vitamin D. (I guess that's good and bad? IDK.)

In 2025, we finally got a proper randomized trial on modern high-SPF sunscreen. I'm sure you all were waiting for this one -- just like the next season of Silo. It's called the Sun-D Trial. In it were 639 adults from Australia. One group was told to put on SPF 50+ every day the UV index was forecast to hit 3 or higher and the other group left to use sunscreen however they normally would. After about a year, the daily group's vitamin D was about 5 nmol/L lower — roughly 2 ng/mL, on the same scale as my 23 — and they were about a third more likely to be deficient.¹ A 2025 review pooling 22 studies landed in the same place, around 2 ng/mL.²

What does that mean for you? You can either apply your sunscreen like an engineer or continue to do as you do. There is some effect, but it's small -- and even more important, this all showed up under a strict daily protocol, applied more diligently than most people ever manage.

One more point. People ask me whether zinc sunscreen lets more vitamin D through than chemical sunscreen. No study has shown that it does. What changes your vitamin D is the SPF and how much you put on, not which filter does the work. (If you want the full mineral-versus-chemical comparison, that's The Real Difference Between Mineral and Chemical Sunscreen; the deeper zinc story is in Is Non-Nano Zinc Oxide Safe?.)

So should you stop wearing sunscreen?

Vitamin D matters — an estimated one billion people worldwide run low on it.⁷ But your favorite health influencer reading that and concluding “sunscreen causes vitamin D deficiency, stop wearing it” is a baby with the bathwater take. Be wary of definitive statements when it comes to your own health. A simple blood test can reveal if your D levels are high or low. No influencer needed.

But back to sunscreen. No, don't stop.

Sure, you might lower your level about 2 ng/mL, which a supplement covers for a few dollars a month. But on the other side lies a higher risk of skin cancer: the most common cancer in the US. At least 1 in 5 Americans will get it by age 70,¹³ and the damage behind it builds up and doesn't reverse.

The long-running Nambour study in Australia is the clearest evidence on the protection side. People assigned to use sunscreen every day ended up with about 40% fewer squamous cell skin cancers than people who used it when they felt like it.³ At the ten-year follow-up, the daily group had roughly half the melanomas, and invasive melanoma — the dangerous kind — was down by about 73%.⁴

Also, the researchers behind the 2025 vitamin D trial, the one that showed sunscreen does lower vitamin D, didn't tell anyone to stop using it. Their advice to people who wear it every day was to keep wearing it and take a vitamin D supplement.¹

There is also some early, small research suggesting sunlight on the skin releases stored nitric oxide, which can relax blood vessels and lower blood pressure for a while.¹¹ It's one small mechanistic study, not a reason to skip protection. I mention it because the position I land on was never “the sun is bad.” Sunburn is the real problem.

How do you get vitamin D and still wear sunscreen every day?

If you're in the right latitude and season, you're already getting more sun than you think. The walk to the car, errands, the spot on your calf you missed, sunscreen applied thinner than the label assumes — ordinary days leak a fair amount of UVB even when you protect. You don't need to go looking for exposure.

If you were going to time it, the hours when UVB is strong enough to make vitamin D are roughly 10 a.m. to 4 p.m., which is also when you burn fastest. The early-morning “vitamin D walk” makes very little.

That's the main reason I don't tell people to schedule sun for vitamin D. You can't get the vitamin D without the UV that comes with it.

If you are out in the sun anyway, more skin showing does more than more time. Your arms and legs make far more than your face and hands alone, which is why the incidental sun on your forearms on a normal day already does real work. Keep deliberate sessions short, since your skin hits its limit in minutes, and stop well before you turn pink. Past pink you're making no more vitamin D, just more damage.

And like I said above, know your calendar. Up here, from roughly October through March, the sun isn't going to make your vitamin D no matter what time you go out or how much skin you show. Ordinary window glass blocks UVB completely, so sitting in a sunny room doesn't count either, and a heavily overcast day makes a lot less.

And if you have darker skin, “just get more sun” is bad advice. It means more exposure for a smaller return. A supplement is the lever that works.

How should you supplement vitamin D?

This is the reliable half of the plan. It's cheap, there's no UV involved, and it works — it's how I went from 23 to over 50.

I'm not your doctor, so I won't give you a dosage. The guideposts are public. In the U.S. the recommended intake for adults is 600 IU a day up to age 70 and 800 IU after, with an upper limit of 4,000.¹⁴ The U.K. keeps it simpler: 400 IU a day, especially October through March. Look for D3 rather than D2, and take it with a meal that has some fat in it.

A few groups get a specific recommendation. The Endocrine Society's 2024 guideline recommends vitamin D supplements for pregnant women and adults over 75, along with children and adults with high-risk prediabetes. It also suggests against routine vitamin D blood tests for healthy adults, including people with darker skin.¹² With that advice, I wouldn't have known the sun wasn't working for my own vitamin D levels and would have ignorantly continued on. So you can decide how valid their suggestion is for yourself.

For most people the plan is simple: protect your skin, take your D, get on with your life outside.

Does sunscreen block vitamin D? Wrapping it up

Does sunscreen block vitamin D? A little. Is that a reason to skip it? No. Get your protection from sunscreen and your vitamin D from a supplement, plus whatever sun you're already getting.

Annmarie and I learned the supplement half of that the hard way in an RV in 2010. The sunscreen half took me a lot longer.

Protection is never supposed to keep you out of the sun. It's what lets you stay out in it. If you want the full daily routine — how much to use, how often to reapply, how to read the UV index — it's in The Sun Lover's Guide to Daily Sun Protection. And we made our sunscreen for exactly that: being outside more, without adding to your risk of skin damage.

Frequently asked questions

Does sunscreen cause vitamin D deficiency?

Only modestly. The first randomized trial of daily high-SPF sunscreen, the 2025 Sun-D Trial, found that people who applied SPF 50+ every day had vitamin D levels about 5 nmol/L (about 2 ng/mL) lower, and a roughly one-third higher rate of deficiency, than people who used sunscreen at their own discretion. The trial's researchers advised continuing to use sunscreen and supplementing vitamin D, not stopping.

What's the best time of day to get vitamin D from the sun?

Roughly 10 a.m. to 4 p.m. is the only window when UVB is strong enough to make vitamin D. It's also when you burn fastest, because the same UVB does both. Morning and late-afternoon sun makes very little vitamin D. That's why most experts suggest protecting your skin and supplementing rather than timing unprotected sun.

Can you get vitamin D through a window or on a cloudy day?

Not through a window — ordinary glass blocks virtually all UVB. On a cloudy or smoggy day you still make some, but less. And above roughly 35 degrees north, winter sun makes essentially none regardless.

Does mineral sunscreen block less vitamin D than chemical sunscreen?

No study has shown that it does. What affects your vitamin D is the SPF and how much you apply, not whether the filter is zinc oxide or a chemical one.

How much vitamin D should I take if I wear sunscreen every day?

U.S. guidelines put adult intake at 600 IU a day (800 IU after 70), with an upper limit of 4,000 IU; the U.K. recommends 400 IU a day, especially in winter. D3 taken with a meal is the usual choice. The Endocrine Society's 2024 guideline recommends supplementing for pregnant women and adults over 75, and suggests against routine vitamin D testing for healthy adults. Your doctor is the right person for a specific dose.

Is it safer to get vitamin D from the sun or from a supplement?

A supplement carries no UV risk. Making vitamin D from sunlight means absorbing UV, which causes cumulative skin damage. For most people, supplementing is the lower-risk way to keep vitamin D up.

About the author

Kevin Gianni is the co-founder of salt+blue and Annmarie Skin Care and the author of Kale and Coffee. He's spent more than twenty years researching natural health and personal-care ingredients — reading studies, interviewing experts, and questioning dubious marketing. (He's also been using em-dashes well before AI made them suspicious, and has no intention of stopping.)

Part of the Sun Lover's Guide to daily sun protection.

References

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