Vitamin D Levels in Scandinavia: Why Testing Matters

# Vitamin D in Sweden – Why Levels Drop in Winter

Living in Scandinavia has many advantages – beautiful nature, strong public services, and a high quality of life. But living at northern latitudes also creates a particular challenge for getting enough vitamin D.

During the darker months of the year, the sun sits too low in the sky for your skin to produce meaningful amounts of vitamin D. As a result, vitamin D levels often fall during winter, particularly in people who get little sun exposure or have a low dietary intake.

Here is why vitamin D matters, how to test your levels, and what you can do if they are low.

Why Are Vitamin D Levels Often Lower in Sweden?

Vitamin D is different from many other vitamins because your body can produce it when your skin is exposed to UVB radiation from sunlight. In Sweden, this ability is significantly reduced in winter.

Several factors can affect vitamin D status:

* **Latitude:** Sweden lies approximately between 55° and 69° north. During winter, the sun's UVB radiation is often insufficient for the skin to produce meaningful amounts of vitamin D. * **Dark winters:** In Stockholm, the sun remains low in the sky during the winter months, while parts of northern Sweden experience very limited daylight during parts of the winter. * **Limited sun exposure:** Even during summer, many people spend much of the day indoors. * **Sun protection:** Sunscreen reduces UVB exposure and therefore also reduces vitamin D production in the skin. * **Skin pigmentation:** People with darker skin generally require longer sun exposure to produce the same amount of vitamin D as people with lighter skin.

Swedish studies show clear seasonal variation in vitamin D levels, with levels generally lower during winter and spring than during summer.

What Does Vitamin D Do in the Body?

Vitamin D is needed for several important functions. It helps the body maintain normal calcium absorption and contributes to normal bone and muscle function. It also contributes to the normal function of the immune system.

Bone Health

Vitamin D helps the body absorb calcium and is important for maintaining normal bones. Severe and prolonged vitamin D deficiency can lead to osteomalacia in adults and rickets in children.

Immune Function

Vitamin D plays an important role in normal immune function. Low levels have been associated in observational studies with a higher occurrence of respiratory infections, but this does not mean that vitamin D supplements can prevent or treat infections.

Muscle Function

Vitamin D contributes to normal muscle function. Severe deficiency can be associated with muscle weakness and muscle pain.

Mood and Wellbeing

Vitamin D status has also been studied in relation to mood and mental wellbeing. However, these relationships are complex, and fatigue or low mood can have many different causes. A low vitamin D level should therefore be considered a possible contributing factor rather than an explanation for these symptoms.

How Do You Test Your Vitamin D Level?

The standard blood test measures **25-hydroxyvitamin D (25-OH-D)**, usually reported in nmol/L in Sweden.

How Can You Interpret the Result?

| Level (nmol/L) | General interpretation | | -------------- | -------------------------------------------------------------------------------------- | | **<30** | Deficiency | | **30–49** | Low | | **50–74** | Sufficient according to clinical guidelines, but below Wellth's practical target range | | **75–125** | Wellth's practical target range | | **>250** | May indicate a risk of excessive intake and should be assessed in context |

Exact thresholds can vary between guidelines and laboratories.

At Wellth, we use **75–125 nmol/L as a practical target range** when assessing vitamin D as part of the bigger health picture. This is a nutritional and lifestyle target, rather than a clinical definition of deficiency.

When Might It Be Useful to Test?

Testing may be particularly relevant if you:

* want to know your vitamin D status during the winter * get little sun exposure * have darker skin * rarely eat vitamin D-rich foods * have a diet or health condition that may affect nutrient absorption * have previously had low vitamin D levels and want to monitor the response to supplementation

Because vitamin D levels are often lowest towards the end of winter, **February–March** can provide a useful picture of your level after the winter months. Testing in late summer can give you an indication of how your levels have responded to summer sun exposure.

What Can You Do If Your Level Is Low?

The first step is to look at your diet, sun exposure, and whether supplementation may be appropriate.

The Swedish Food Agency recommends vitamin D supplements for certain risk groups and gives different recommended intakes depending on age and risk factors. Individual needs vary, and taking a higher dose is not automatically better.

If you take vitamin D regularly, repeating the blood test after around **8–12 weeks** can show how your level has changed and whether your intake needs adjusting.

Vitamin D3 (cholecalciferol) is the form commonly used in supplements. Because vitamin D is fat-soluble, it can be taken with a meal containing some fat.

Food Sources of Vitamin D

Diet can contribute to your vitamin D intake, although it can be difficult to obtain sufficient amounts from food alone.

Good sources include:

* **fatty fish**, such as salmon, mackerel, and herring * **egg yolks** * **vitamin D-fortified dairy products and plant-based drinks** * **fortified spreads and fats** * some **UV-exposed mushrooms**

Fatty fish can therefore be a valuable part of your diet, but during the darker months, dietary intake may need to be supplemented depending on your individual needs and vitamin D status.

Vitamin D in the Bigger Picture

Vitamin D is only one part of the picture. When reviewing your blood tests, it can also be useful to consider other markers and factors that influence your nutritional status and overall health.

For example, **magnesium and calcium** play important roles in the body's normal functions, while diet, sun exposure, and individual health all influence vitamin D status.

This is why a single test does not always tell the whole story. At Wellth, we look at vitamin D alongside other relevant blood markers, your health, diet, and lifestyle to build a more complete picture.

Key Takeaways

* Vitamin D levels often fall during the Swedish winter. * Vitamin D is important for bones, muscles, and normal immune function. * **25-OH-D** is the standard blood test used to assess vitamin D status. * **50 nmol/L** is an important threshold for adequate levels in many clinical contexts. * At Wellth, we use **75–125 nmol/L as a practical target range**. * The need for supplementation varies between individuals – higher doses are not automatically better. * A repeat test after **8–12 weeks** can show how your level has responded to supplementation. * Vitamin D status should be considered alongside diet, lifestyle, and other relevant health markers.

Living at northern latitudes means that vitamin D is worth paying attention to, particularly during the winter months. A simple blood test can show where you stand and provide a better basis for deciding whether you need to change your intake.