Are you getting enough vitamin D? What to do as the days get shorter
- Kat Storr
Published: September 11, 2026 at 10:48 AM
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We asked the experts how to ensure your your vitamin D levels stay topped up all year round.
The long, hot summer meant we had plenty of time to boost our vitamin D levels, but as autumn and winter draw closer, those of us living in the northern hemisphere can no longer rely on the sun to keep our bones and muscles healthy.
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The shortest days of winter will give us just eight hours of daylight and, even when it is light, the sun’s rays are much weaker than they are during high summer. While our bodies can store some vitamin D, the amount is unlikely to last us through the darker months, which is why doctors are so keen for us to use other ways to keep our levels up all year round.
NHS GP and women’s health specialist Dr Deepali Misra-Sharp says vitamin D plays a “key role in regulating calcium and phosphate” in our bodies. If we don’t get enough of it, we’re putting ourselves at risk of health problems such as osteoporosis, bone fractures and, in children, rickets. “There's also growing evidence linking vitamin D to immune function, mood and muscle strength, though the research on these ‘extra-skeletal’ effects is still evolving,” she explains.
From late March to September, we should be able to make all of the vitamin D we need from sunlight. However, the Department for Health and Social Care recommends that everyone in the UK takes a supplement from October to March. The NHS says children from the age of one and all adults need 10mcg of vitamin D a day. It’s also safe for pregnant and breastfeeding women to take.
It’s estimated that one in six adults and 20 per cent of children are deficient in vitamin D, and these figures will rise in winter. As well as taking the supplements mentioned above, what we eat can also keep our vitamin D levels up during the next few months and help us avoid any future health problems.
How to boost your vitamin D levels
Dr Misra-Sharp says oily fish like salmon, mackerel and sardines are one of the best sources of vitamin D. Other foods include egg yolks, fortified foods like cereals, spreads and plant milk, which have added vitamin D. Red meat and liver (in small amounts) also contain vitamin D, as well as mushrooms, which have been exposed to UV light. But the GP adds that “food alone rarely provides enough – diet typically contributes far less than sunlight or supplementation”.
As we mentioned above, vitamin D is needed to help our gut absorb calcium. “There's little benefit to boosting vitamin D if calcium intake is also poor,” says Dr Misra-Sharp. “Magnesium is also needed as a co-factor to convert vitamin D into its active form, and vitamin K2 is thought to help direct calcium to bones rather than soft tissue, though the evidence here is less robust.” Supplements aren’t necessary for these two nutrients, as we can get both of them by eating plenty of leafy green vegetables, dairy products and nuts and seeds.
When it comes to choosing a vitamin D supplement, it’s worth knowing that there are two types you’ll see on a label: D2 and D3. The one you want to choose is D3 (cholecalciferol), because this is what our skin makes when it’s exposed to sunlight. Vitamin D2 has also been shown to break down quicker than D3. Our health experts have tried and tested the best vitamin D supplements, which come in a variety of formats – from sprays and oils to capsules – to help you find the best one to buy that suits you.
Research has also shown that people who exercise regularly experience less of a drop in vitamin D levels from summer to winter compared to those who don’t exercise. The 10-week study, published in Advanced Science in May 2025, looked at the results from two groups of overweight participants who either exercised four times a week or not at all. The experts found that the group who exercised experienced a 15 per cent drop in their vitamin D levels compared to a 25 per cent drop among those who did none.
It can feel harder to get motivated to exercise during winter, but if you want to protect your vitamin D levels, why not try a brisk walk or bike ride, or jog around the park a few times a week?
Can you have too much vitamin D?
While you can’t overdose on vitamin D via sunlight, it's possible to take too much of it, although toxicity is rare. Dr Misra-Sharp says: “Taking very high doses over a long period can lead to a build-up of calcium in the blood (hypercalcaemia), causing nausea, weakness, kidney problems and, in severe cases, kidney stones or damage.” The NHS advises that adults shouldn’t take more than 100mcg (4,000IU) per day. The 10mcg we suggest above is sufficient. Children aged one to 10 should not exceed 50mcg (2,000IU) a day.
And, while sunlight is good for us, always remember to use a SPF or cover up if you’re spending a lot of time outside in the sun to reduce your risk of skin cancer. Speak to your doctor about how much you should take if you’ve been diagnosed with a deficiency. People with darker skin, those who live in a care home or don’t go outside much, or who keep their skin covered up should take a supplement all year round.
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Kat Storr
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