Q&A on Vitamin D

Our Nutritionist's perspective:

One of the biggest mistakes I see people making with vitamin D is waiting until they get sick before they start thinking about it. Vitamin D plays an important role in normal immune function and, because in the UK our ability to make vitamin D from sunlight becomes very limited from around October through to early spring, now is actually a really good time to start paying attention to your levels.

Sunlight exposure, diet, lifestyle and individual circumstances can all influence your vitamin D status, so rather than guessing, one thing I really encourage people to consider is a simple at-home vitamin D blood test. It’s such a quick and easy way to understand where your levels are as we head into winter, and you can then supplement appropriately for you.

When choosing a supplement, I like vitamin D3 paired with K2 because they work really well together. Vitamin D3 helps your body absorb calcium from the foods you eat, while K2 activates proteins that help bind calcium into the bones so together they play complementary roles in supporting bone health. 

What does Vitamin D do? 

Vitamin D is an essential nutrient with several important roles in the body. It contributes to the normal function of the immune system and also plays an important role in bone health contributing to the maintenance of normal bones and teeth, muscle function and helping the body absorb and utilise calcium and phosphorus, both are essential minerals for healthy bones and teeth.

Why might Vitamin D be particularly relevant during winter?

Our bodies can make vitamin D when our skin is exposed to UVB rays from sunlight. However, in the UK during autumn and winter, the sun sits lower in the sky and not enough UVB reaches us for our skin to make sufficient vitamin D. This is why the NHS recommends that most adults consider taking a daily 10µg (400 IU) vitamin D supplement during this period.

Winter can therefore be a useful time to think about vitamin D as part of your nutritional foundations, alongside a varied diet and spending time outdoors when possible.

How much Vitamin D do I need?

For adults and children over four, UK government guidance recommends 10µg (400 IU) of vitamin D per day during autumn and winter. Some people are advised to consider taking this amount throughout the year, including those with limited exposure to sunlight and people with darker skin.

It’s important to distinguish general supplementation advice from treatment for a confirmed deficiency. If a blood test shows that your vitamin D level is low, your healthcare professional may recommend a different dose based on your individual needs.

Should I take Vitamin D3 or D3 + K2?

Vitamin D3 is a form of vitamin D commonly used in supplements. Vitamin K2 is a specific form of vitamin K, and the two nutrients have complementary roles in bone health. Vitamin D helps the body absorb calcium, while vitamin K contributes to the maintenance of normal bones and normal blood clotting.

This is why you’ll often see vitamin D3 and K2 combined in the same supplement.

The right choice for you will depend on your diet, existing supplements, individual nutritional needs and circumstances.

Should I test my Vitamin D levels?

Testing can be useful to understand your Vitamin D status, especially if you have risk factors for deficiency or are concerned about your levels.

A blood test measures 25-hydroxyvitamin D, the main marker used to assess Vitamin D status. If you are considering testing, it's worth discussing the result with a qualified healthcare professional who can put it into context.

UK clinical guidance uses blood Vitamin D testing selectively rather than as a routine test for everyone.

What should I look for in a Vitamin D supplement?

Look at the form of vitamin D, the dose, additional ingredients and how it’s delivered.

It’s also worth choosing a format you’ll actually take consistently. An oral spray, for example, can be a convenient option if you don’t enjoy swallowing capsules or simply want something that’s easy to incorporate into your daily routine.