How much vitamin D do UK adults actually need in winter?

Between October and early March, sunlight in the UK is too weak for your skin to make meaningful vitamin D. That is not a marketing line — it is why the NHS recommends that everyone in the UK considers a daily vitamin D supplement through autumn and winter.

What the NHS says

The NHS advises adults to consider 10 micrograms (400 IU) of vitamin D a day from October to March, and notes that people who are rarely outdoors, cover their skin, or have darker skin may be short all year round. It also sets an upper safe limit for adults of 100 micrograms (4000 IU) a day.

So why is QUAKE D3+K2 4000 IU?

400 IU is the minimum to avoid deficiency. Many adults who work indoors, do long or night shifts, or train hard start winter already low, and a maintenance dose will not move that. 4000 IU (100µg) sits at the NHS upper safe limit for adults — high enough to make a difference, and not above it. Each QUAKE gummy delivers exactly that in one serving, so there is no guessing and no stacking tablets.

If you have a diagnosed condition, are pregnant, or take medication that affects calcium or vitamin D, speak to your GP or pharmacist before starting any supplement. And if you also take our Multivitamin (which contains 50µg of D3), take one or the other each day, not both — our Stack Safety Check adds it up for you.

Why we add K2

Vitamin D helps your body absorb calcium. Vitamin K contributes to the maintenance of normal bones and to normal blood clotting. We use K2 in the MK-7 form (140µg per gummy) because it stays active in the body longer than the MK-4 form, so one gummy a day covers it.

How to take it

  • One gummy a day, ideally with a meal that contains some fat — vitamin D is fat-soluble.
  • Chew it. No water needed.
  • Keep going through to March. Consistency matters more than timing.

Each jar is 60 gummies: a full two-month supply, available in Natural Orange or Natural Lemon.

Vitamin D contributes to the maintenance of normal bones and teeth and to the normal function of the immune system. Vitamin K contributes to the maintenance of normal bones. Food supplements should not replace a varied, balanced diet and a healthy lifestyle.

Sources & further reading

  1. NHS — Vitamin D: the 10µg autumn-winter advice, who is at risk all year, and the 100µg (4,000 IU) adult upper limit.
  2. SACN — Vitamin D and Health (2016): the UK Scientific Advisory Committee on Nutrition report the NHS guidance is based on.
  3. GB Nutrition and Health Claims Register: the authorised wording for what vitamin D and vitamin K can legally be said to do.
  4. NHS — Vitamin K: what it does and how much adults need.

We link to public health sources rather than to studies we have cherry-picked. If a source changes, we update the article.

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