Vitamin D in summer: do you still need to supplement?

May, June, the sun climbs higher and it gets warmer and warmer. In the morning you reach for your vitamin D supplement, which you have faithfully been taking since autumn, and suddenly a thought comes: "Wait, there is plenty of sun now. The skin makes vitamin D on its own. Why do I still need a tablet?". Maybe it really is time to put the supplement away until October?

This is one of the most frequently asked questions about supplementation - and contrary to appearances, the answer is not simply "yes, stop it in summer". Because "it is summer and the sun is shining" is only the start of the equation. What matters is how much sun really reaches your skin, at what time of day, how large an area is exposed and what is on it.

This article looks at vitamin D solely from the summer perspective - it answers the specific question: "can I stop the supplement in summer?". If you are looking for information about deficiency symptoms and the year-round approach, we have a separate article on that. Here we focus on the sunny season.

Where does vitamin D from the sun even come from?

Vitamin D is exceptional in this respect - it is the only "vitamin" the body can produce on its own. This happens in the skin under the influence of ultraviolet radiation, specifically its UVB fraction. When UVB rays fall on exposed skin, they trigger a reaction that leads to the formation of vitamin D.

This sounds like a simple deal with nature: expose your skin to the sun and you get vitamin D for free. And indeed, in summer the skin can make quite a lot of it. The problem is that this production depends on many conditions - and some of them are not met at all in real, everyday life.

Why in summer it is not so simple at all

"Summer = vitamin D sorted" is a convenient simplification. Let us look at why in practice it tends to be unreliable.

Sunscreens block synthesis

This is an apparent paradox. Sunscreens protect the skin from burns and reduce the risk of skin cancer - and that is very good, because you should use them. But the UV filter, by blocking UVB radiation, also limits vitamin D synthesis along the way. The higher the SPF and the more thoroughly you cover your skin, the less UVB reaches it.

This is not an argument for giving up sunscreen - quite the opposite. Protecting the skin from the sun is more important than "topping up" vitamin D through sunbathing. It is rather an argument that if you use sunscreen responsibly, you cannot at the same time count on the sun fully covering your need for vitamin D.

You work indoors

Think honestly about how many hours between 10:00 and 15:00 on a typical working day you really spend outside, with exposed skin. For many people the answer is: a few, a dozen or so minutes - the way to work, a short walk during a break. The rest of the day passes in the office, the shop, the car, at home. A window pane does not help - it does not let through UVB in the amount needed for vitamin D production. "It is summer" does not automatically mean "I am in the sun".

Short exposure and exposed area of skin

The amount of vitamin D produced depends not only on time in the sun, but also on how large an area of skin is exposed. A short outing in long sleeves is something quite different from a longer stay in clothing that leaves arms and legs uncovered. So "I was outside today" on its own does not say much - ten minutes in a hooded sweatshirt is a modest contribution to synthesis.

The latitude of Central Europe and the time of day

Central Europe lies relatively far north. This means that even in summer the sun favours vitamin D production only at certain hours - roughly in the middle of the day, when it is high and UVB rays effectively reach the surface of the earth. In the morning and late afternoon, when the sun is low, synthesis is negligible, even though it is still bright and warm outside. A walk at 18:00 will give you pleasure and exercise, but little vitamin D.

Other factors

The efficiency of vitamin D production in the skin is also influenced by a few other things:

• Skin tone - melanin acts as a natural UV filter, so people with darker skin need a longer exposure to produce the same amount of vitamin D
• Age - with age the skin's ability to synthesise vitamin D decreases, which is why older people are more at risk of deficiency even in summer
• Weather and cloud cover - a thick layer of cloud limits the amount of UVB reaching the skin
• Body weight - vitamin D is fat-soluble, and in people with a large amount of fat tissue it tends to be less available to the body

The conclusion from this list is one: in summer you can in theory cover your need for vitamin D from the sun, but in practice this does not happen for many people. That is why the decision "to stop or not" should be conscious, not automatic.

What the recommendations on supplementation say

Expert recommendations on vitamin D are quite practical and take our climate into account. Their logic can be summed up as follows: under Central European conditions, vitamin D supplementation is recommended at least during the autumn and winter months, when skin synthesis practically does not take place. In summer, supplementation may not be necessary for some people - but only when adequate exposure of the skin to the sun is actually ensured.

And here is the heart of the matter: "adequate exposure" means, in simplified terms, regular time in the sun around midday, with a considerable area of skin exposed (e.g. forearms and shins), without sunscreen, for a dozen to several dozen minutes. If your summer does not look like that - and for many people it does not - a break in supplementation may simply mean several months with a low vitamin D level.

Who should supplement all year round - including in summer

There are groups of people for whom year-round vitamin D supplementation is particularly recommended, regardless of the season:

• Older people - the skin produces less vitamin D, and sun exposure tends to be limited
• People who work indoors and spend most of the day inside buildings
• People who consistently use sunscreen and avoid the sun (e.g. for dermatological reasons)
• People with darker skin living in Central Europe
• People with obesity
• People with illnesses or taking medicines that affect vitamin D balance - here the decision is made by a doctor
• Pregnant and breastfeeding women - in line with the recommendations of the attending doctor
• Infants - supplementation is carried out all year round in line with the paediatrician's recommendations, because small children are not exposed to direct sunlight

If you belong to one of these groups, summer is rather not the moment to stop the supplement - unless a doctor recommends otherwise.

For whom summer may be an exception

A break in supplementation during the summer months can be considered for a person who really spends a lot of time in the sun - for example works outdoors, exposes their skin regularly and at the right time of day, does not belong to a risk group and has a normal vitamin D level. Even then, a safer approach than "I am guessing" is to check the vitamin D level with a test - more on that in a moment.

Dosage - adults and children

The specific dose of vitamin D depends on age, body weight, the health situation and the current blood level, which is why it is best to set it with a doctor or pharmacist. Below is a general picture of how it looks - it does not replace individual advice.

Adults

In healthy adults, moderate doses of vitamin D taken regularly are usually used as prevention - as a rule on the order of about 1000 to 2000 IU per day, with adjustment depending on body weight and the season. Higher doses are sometimes recommended for people in risk groups and in case of a confirmed deficiency - but that is already a situation in which a test and a doctor's recommendation are needed, not increasing the dose on your own.

Vitamin D is best taken together with a meal containing fat - this improves its absorption, because it is a fat-soluble vitamin.

Children

In children, the dosage of vitamin D depends above all on age and body weight, and in the youngest it is carried out all year round. Doses for children are set individually - here it is especially important not to be guided by "adult" doses and not to improvise. Ask the paediatrician about the right dose for your child, and reach for a product in the version intended for the given age (e.g. drops for infants).

What to keep in mind with dosage

• Vitamin D, like any fat-soluble vitamin, should not be taken in arbitrarily high doses "in reserve" - it accumulates in the body
• Very high doses over a long time can lead to an excess of vitamin D and a raised calcium level in the blood - which is why higher doses are used under medical supervision
• If you take a combination product (e.g. a multivitamin), check how much vitamin D it already contains, so as not to double the doses
• A fixed time of taking it and a meal with fat are easier to turn into a habit than taking it "when you remember"

When it is worth testing your vitamin D level

Instead of guessing whether the sun is enough in summer, you can simply check it. The vitamin D level is assessed by a blood test that measures 25(OH)D - this is a reliable indicator of the body's vitamin D supply. The test is widely available, does not require a referral and is not expensive.

It is worth considering such a test when:

• You do not know whether, in your case, to stop the supplement in summer or to continue it
• You belong to a risk group for deficiency
• You have symptoms that may be linked to deficiency (we write about the symptoms in detail in a separate article)
• You supplement higher doses and want to make sure the level is within the safe range
• You are planning a break in supplementation and want to have a reference point

The test result lets you make the decision consciously - and, if needed, choose the dose together with a doctor instead of acting "by feel".

Most frequent questions

Can I really stop vitamin D in summer for sure?

There is no single answer for everyone. If you spend a lot of time in the sun, regularly, around midday, with exposed skin, do not belong to a risk group and have a normal vitamin D level - a break in summer is sometimes justified. If you work indoors, consistently use sunscreen or belong to a risk group - summer is rather not a good moment to stop. If in doubt, check the level with a test and ask a doctor.

Are 15 minutes of sun a day enough?

It depends on the time of day, the exposed area of skin, the skin tone, the age and whether you use sunscreen. A short exposure in the middle of the day, with uncovered forearms and shins, without cream, can be a real contribution to synthesis. The same 15 minutes in the evening, in long sleeves, will give very little. "15 minutes" without these details is too little to decide anything.

Does sunscreen really block vitamin D?

The UV filter, by limiting UVB radiation, also limits vitamin D synthesis in the skin. This is, however, not a reason to give up sunscreen - protecting the skin from burns and cancer is more important. A sensible approach is to use sunscreen and at the same time take care of vitamin D in another way, that is, most often through supplementation.

Can I overdose on vitamin D by supplementing it in summer despite the sun?

Vitamin D synthesis in the skin is naturally regulated - you cannot overdose on it through sunbathing alone. An excess can, however, result from taking very high doses from supplements over a long time. With moderate preventive doses the risk is small, but this is another argument for not using higher doses "on your own" and not doubling products.

How am I supposed to know which dose to choose in summer?

The surest path is to set the dose with a doctor or pharmacist, ideally based on the result of a 25(OH)D test, age and body weight. Dosing "by eye" with a fat-soluble vitamin is not a good idea - neither in one direction nor the other.

Summary - what is worth remembering?

✅ "It is summer" does not automatically mean "vitamin D is sorted" - what counts is the real exposure of the skin, not the season alone.

✅ Sunscreens, working indoors, short exposure and the time of day mean that for many people skin synthesis in summer is lower than it seems.

✅ Some people should supplement all year round - among others seniors, people who work indoors, who use sunscreen, from risk groups, pregnant and breastfeeding women and infants.

✅ Summer is sometimes an exception - but only for people who really do spend a lot of time in the sun in the right way, without risk factors.

✅ Set the dose individually - with a doctor or pharmacist, taking age and body weight into account; for children the dose is chosen by a paediatrician.

✅ Instead of guessing - test your 25(OH)D level - this is a simple way to make the decision consciously.

✅ Do not improvise with high doses - vitamin D accumulates in the body, higher doses are used under medical supervision.

Disclaimer

This information is educational in nature and does not replace a medical consultation. The decision about vitamin D supplementation, stopping it during the summer months and about the specific dose is best made with a doctor or pharmacist, if needed based on the result of a vitamin D level test. Dosage in children is set by a paediatrician. Do not use high doses of vitamin D on your own.

Vitamin D in summer is not a question of "yes or no", but of "what really reaches my skin" - and once you have made a conscious decision, it is worth making the purchase itself just as well thought through. Vitamin D products - drops, capsules, forms combined with vitamin K2 - can differ in price from pharmacy to pharmacy, and on the scale of a year and with supplementation for the whole family these are real amounts.

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