Vitamin D in autumn: what does the NHS actually say?

From October to early March the NHS says UK sunlight isn't strong enough. Here's the actual guidance, and how far food really gets you.

Gizella Nagyne Palinkas

9/8/20266 min read

From about October to early March, the NHS says sunlight in the UK is not strong enough for your body to make vitamin D, and advises that everyone consider taking a daily supplement containing 10 micrograms through autumn and winter. Food can contribute meaningfully but rarely covers it on its own — one portion of oily fish is roughly a day's worth, and almost nothing else on the list comes close.

That is the whole of the official position, and it is considerably less dramatic than the version that circulates every September. No panic, no deficiency crisis, no supplement you must buy by Friday. A specific window, a specific amount, and the word consider.

The window is a date range, not a feeling

The NHS is precise about the calendar. From late March or early April to the end of September, most people in the UK can make enough vitamin D from sunlight on their skin. From October to early March, they cannot — the sun does not get high enough in the sky for long enough.

This is why the advice is seasonal rather than year-round for most people, and why it arrives at the same point every year regardless of the weather. A mild October does not extend the window — it is about the angle of the sun, not the temperature. Which makes this worth knowing in early September: you have a few weeks of the current window left, and then the guidance changes.

Some people are advised to take it all year

The NHS lists groups for whom the advice runs year-round rather than seasonally:

Babies up to one year old, unless they are having 500ml or more of infant formula a day
All children aged 1 to 4
People who are rarely outdoors
People in care homes and similar settings
People who usually wear clothing that covers most of their skin when outdoors
People with dark skin

If you are in one of those groups, or you have someone in your household who is, that is worth raising at your next appointment rather than at the end of October.

Can you just eat it?

This is the question that actually matters, and it has a real answer.

The NHS lists oily fish (salmon, sardines, trout, herring, mackerel), red meat, egg yolks, liver, and fortified foods such as some spreads and breakfast cereals as dietary sources. Put actual numbers against a standard portion of those and the shape of it becomes obvious:

Rainbow trout, 85g — 645 IU, about 16.1 µg. Comfortably over.
Salmon, 85g — 383 to 570 IU, about 9.6 to 14.3 µg. Roughly a day's worth on its own.
Canned sardines, 85g — 164 IU, about 4.1 µg. Useful, not sufficient.
Fortified soy milk, 1 cup — 119 IU, about 3.0 µg.
Fortified 1% milk, 1 cup — 117 IU, about 2.9 µg.

(Those food figures come from US Dietary Guidelines data drawn from USDA FoodData Central, converted to micrograms at the source's own stated rate of 40 IU = 1 µg.)

So the honest answer is: yes, you can reach 10 µg from food — provided oily fish appears on your plate most days of the week. If it appears twice a week, which is roughly what most people who eat fish actually manage, the arithmetic does not get there on its own, and the NHS says as much: dietary sources alone are generally not enough through the darker months.

One oddity worth mentioning: mushrooms range from 0 to 1,110 IU per cup depending on UV exposure. That spread is too wide to plan around, though UV-treated ones sold specifically for this are a real thing.

The number that matters in the other direction

The NHS also gives an upper limit: adults should not take more than 100 micrograms (4,000 IU) a day, as more than that could be harmful.

That is worth knowing because the supplement aisle in October does not distinguish carefully between the 10 µg the guidance describes and the very high-dose products sitting next to it. More is not better here, and the ceiling is published for a reason.

What to do about any of this is a conversation for your GP or pharmacist, not an article. That is especially true if you take other medicines, have a condition that affects how you absorb things, or are pregnant. Nothing here is a recommendation to start, stop, or change anything you are taking.

What actually changes in your week

The practical version, for the next few weeks specifically:

Use the window you still have. Until the end of September the sunlight still counts. A walk at lunchtime is worth more in the next three weeks than it will be in November.
Count your oily fish honestly. Not "I should eat more fish" — how many portions did you actually have in the last seven days? That number tells you whether food is doing the work.
If you want it to be more, make it easy. Tinned sardines and tinned salmon require no cooking and no planning. Smoked mackerel needs a fork. This is the least demanding change available in the whole of nutrition.
Read the label before you buy anything. Check the microgram figure, not the IU number on the front, and know where 10 sits relative to the 100 ceiling.
Ask, if you are in one of the year-round groups. That is a different conversation from the general one, and it is worth having properly.

Where the September energy dip actually comes from

Worth saying plainly, because this is the season for it: vitamin D gets blamed every autumn for a great deal it has not been shown to cause. The NHS guidance is about vitamin D's role in bone, muscle and tooth health. It is not framed as an energy intervention, and this article is not going to frame it as one either.

Autumn genuinely does change how the week feels — the light goes, the evenings shorten, the routine gets denser. Those are real and they are worth taking seriously on their own terms. Attaching all of it to one nutrient is tidier than it is true.

This is general information, not medical advice. If you are worried about your energy, or something has changed and stayed changed, speak to your GP rather than reaching for a supplement first.

How much is your autumn actually built?

Six questions about light, food, movement and routine as the season turns, and you land in one of four positions with three things to do next. Two minutes, nothing collected.

Frequently asked questions

When exactly should I start thinking about vitamin D in autumn? The NHS frames the change as happening around the start of October: from late March or early April to the end of September most people in the UK can make enough vitamin D from sunlight, and from October to early March they cannot. So the honest answer is that the last few weeks of September are the tail of the sunlight window and October is when the guidance changes. That makes early September a good moment to look at what you are actually eating rather than a moment to panic.

Can I get enough vitamin D from food alone? It is possible but demanding. A standard 85g portion of salmon supplies roughly 9.6 to 14.3 µg and rainbow trout about 16.1 µg, so a portion of oily fish is around a day's worth by itself. Canned sardines at about 4.1 µg and fortified milks at around 3 µg per cup contribute but do not cover it. If oily fish is on your plate most days, food can get you there. Twice a week, it generally does not, and the NHS says dietary sources alone are usually insufficient through the darker months.

How much vitamin D does the NHS actually recommend? The NHS advises considering a daily supplement containing 10 micrograms during autumn and winter, and states that adults should not exceed 100 micrograms (4,000 IU) a day because more could be harmful. Note the wording is "consider" rather than "must" — it is public health guidance for a population, not a prescription for an individual. What is right for you specifically, particularly alongside anything else you take, is a question for your GP or pharmacist.

Is 1,000 IU the same as 10 micrograms? No. The standard conversion, which the US Dietary Guidelines data uses, is 40 IU to 1 microgram, so 10 µg is 400 IU and 1,000 IU is 25 µg. This trips people up constantly because supplement packaging uses both units and often leads with the larger-looking number. When you are comparing products, convert everything to micrograms first, then compare — and check where the result sits relative to the 100 µg ceiling.

Does sitting by a sunny window count? The NHS guidance is about sunlight on skin, and it is specific that from October to early March UK sunlight is not strong enough for the body to make vitamin D regardless. Glass is not the deciding factor in autumn and winter — the position of the sun is. Getting outside during daylight is worth doing for plenty of other reasons through a dark season, and Health & Fitness with Ella will always argue for the lunchtime walk, but it is not a substitute for the seasonal guidance.

Is vitamin D why I feel flat in October? It gets blamed for a great deal it has not been shown to cause. The NHS guidance concerns vitamin D's role in bone, muscle and tooth health rather than energy, and this article is not going to claim otherwise. Autumn does genuinely change how a week feels — less light, shorter evenings, a fuller routine — and those are worth addressing directly. If something has changed and stayed changed, that is one for your GP rather than the supplement aisle.

For the weeks when the light goes

The Mom Energy Reset Checklist is a five-minute-a-day routine for the stretch of the year when the evenings close in and it all gets harder to hold on to.

Free, and complete → Mom Energy Reset Checklist

When you want the whole month planned

30 Days Body Reset is a full month laid out day by day — movement, food and routine — built for coming back to it in autumn rather than starting from scratch in January.

The full thirty days, laid out day by day → 30 Days Body Reset — €12.99