Vitamin D

Vitamin D is essential for keeping your body functioning properly, yet many people in the UK do not get enough of it. This is rarely due to poor diet or neglect. Instead, it reflects where we live, how much time we spend indoors, and the limited sunlight available for much of the year.

Understanding what vitamin D does, why deficiency is common, and how to maintain healthy levels can help you make sensible, informed choices about your health - without unnecessary worry or confusion.

What is vitamin D?

Vitamin D is a nutrient your body needs for normal day-to-day function. Unlike most vitamins, your body can produce vitamin D itself when your skin is exposed to sunlight. This is why it is often referred to as the "sunshine vitamin".

Once vitamin D is made in the skin or taken in through food or supplements, it is converted into an active form that helps regulate several important processes in the body. In simple terms, vitamin D helps your body absorb calcium, supports muscle function, and plays a role in immune health.

There are two main forms of vitamin D:

Vitamin D3 (cholecalciferol) – made in the skin from sunlight and found in some animal foods
Vitamin D2 (ergocalciferol) – found in certain plant sources and fortified foods

Both forms can raise vitamin D levels, but vitamin D3 is generally more effective at maintaining those levels over time. This is why most supplements contain vitamin D3.

Why vitamin D matters for everyday health

Vitamin D supports several areas of health that affect how you feel and function in everyday life.

One of its most important roles is helping the body absorb calcium. Without enough vitamin D, calcium from food cannot be absorbed efficiently, even if your diet contains plenty of it. Over time, this can weaken bones and increase the risk of fractures, particularly as we get older.

Vitamin D also contributes to normal muscle function. Low levels are linked with muscle weakness, especially in the legs and hips, which can affect balance and confidence with routine movements such as climbing stairs or standing up from a chair.

In addition, vitamin D plays a supporting role in immune health. It helps regulate immune responses rather than "boosting" immunity in an exaggerated way. Adequate vitamin D supports the immune system as part of a balanced lifestyle.

Why vitamin D deficiency is common in the UK

Vitamin D deficiency is widespread in the UK, particularly during autumn and winter. Several overlapping factors make it difficult for people to maintain healthy levels throughout the year.

The most important reasons include:

Limited sunlight from October to March, when the sun is too low in the sky to trigger vitamin D production
Indoor lifestyles, with many people spending most daylight hours at work or commuting
Reduced skin exposure due to clothing, sunscreen use, or cultural practices

Skin tone also plays a role. People with darker skin require longer sun exposure to produce the same amount of vitamin D, which increases the risk of deficiency in the UK climate.

Signs you might be low in vitamin D

Low vitamin D levels do not always cause noticeable symptoms. When symptoms do occur, they tend to be general and easy to attribute to other causes.

People sometimes report:

Ongoing tiredness or low energy
General muscle aches or weakness
A gradual increase in bone or joint discomfort

These symptoms are not specific to vitamin D deficiency and can have many possible explanations. Feeling tired or achy does not automatically mean your vitamin D levels are low, which is why routine testing is not recommended for most people.

For the majority of adults, following public health advice on supplementation is a more practical approach than seeking blood tests.

Vitamin D from sunlight

During late spring and summer, sunlight can help your body make vitamin D.

Between April and September, short periods outdoors with some skin exposed can support vitamin D production. Midday sunlight is most effective, and brief exposure is usually sufficient. You do not need a tan, and you should never allow your skin to burn.

In practice, relying on sunlight alone is unreliable in the UK. Weather, work patterns, and long winters mean that many people cannot maintain healthy vitamin D levels without additional support.

Vitamin D from food

Only a small number of foods naturally contain vitamin D, which makes it difficult to meet daily needs through diet alone.

Foods that provide vitamin D include oily fish, egg yolks, and some fortified products such as breakfast cereals or plant-based milk alternatives. While these foods are useful as part of a balanced diet, they typically provide only small amounts of vitamin D.

As a result, most people in the UK do not reach recommended intake levels through food alone.

Vitamin D supplements: what you need to know

Because sunlight and diet are often not enough, UK health guidance recommends vitamin D supplementation for much of the population.

Adults and children over four years old are advised to take 10 micrograms (400 IU) per day, particularly during autumn and winter. This amount is sufficient to support bone and muscle health for most people.

Many supplements provide between 10 and 25 micrograms daily, which is considered safe for general use. Vitamin D3 is usually preferred, and vegan vitamin D3 options derived from lichen are available.

Pharmacist comment

"Vitamin D is one of the most common supplements we recommend in pharmacy, simply because it’s so difficult to get enough from sunlight and food alone in the UK. A daily dose of 10 micrograms is safe, affordable, and supports long-term bone and muscle health for most people. Higher doses are rarely needed unless advised by a healthcare professional." - Alessandro Grenci, Superintendent Pharmacist

Can you take too much vitamin D?

Vitamin D toxicity is rare and usually only occurs when very high doses are taken over long periods.

For adults, the safe upper limit is 100 micrograms (4000 IU) per day. The recommended intake of 10 micrograms sits well below this, providing a wide safety margin. Problems generally arise only when people take multiple high-dose supplements without realising.

Who should consider vitamin D supplements most?

While vitamin D can be helpful for many people, some groups are advised to take supplements all year round, including:

People who spend little time outdoors
Adults aged 65 and over
People with darker skin tones
Those who regularly cover most of their skin

Pregnant and breastfeeding women are also advised to take 10 micrograms daily to support both maternal health and their baby’s development.

When to speak to a healthcare professional

You should seek advice from a pharmacist or GP if you have ongoing symptoms that do not improve, if you have conditions affecting the kidneys or nutrient absorption, or if you are taking other supplements or medicines that may interact.

A healthcare professional can help confirm the most appropriate dose for your individual circumstances.

Final thoughts

Vitamin D plays a quiet but essential role in keeping bones, muscles, and the immune system functioning normally. In the UK, it is difficult to maintain healthy levels through sunlight and diet alone.

For most people, a daily supplement providing 10 micrograms of vitamin D, particularly during the autumn and winter months, is a simple, evidence-based way to support long-term health without unnecessary complexity.