Wellness · Nutrition
Vitamin D, the UK guidance, plainly.
From October to March, the UK sun cannot make enough vitamin D. Here is who should supplement, how much, and when a blood test is worth it.
Why trust this guide
- 01
Clinically reviewed
Written by our editorial team and reviewed by a registered UK clinician before publication.
- 02
Sourced from UK guidance
Grounded in SACN 2016, NICE CKS and NHS advice — not supplement marketing.
- 03
Practical, not pushy
Clear on who benefits, who does not, and when a blood test is actually worth it.
Key facts
Vitamin D at a glance.
Six things worth knowing before you buy a bottle of anything — the UK guidance, in plain English.
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Why UK winters need it
Between October and March, UK sunlight is too weak for the skin to make enough vitamin D — latitude, not weather, is the reason.
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UK Government advice
10 µg (400 IU) daily October–March for all adults and children over 4 — from a supplement, not diet alone.
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Higher-risk groups
Darker skin, housebound or care-home residents, and those who cover their skin outdoors should supplement year-round.
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Food sources
Oily fish, egg yolk, red meat, liver and fortified spreads — useful, but never enough on their own in winter.
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Symptoms of deficiency
Bone pain, muscle weakness, persistent fatigue and low mood — non-specific, and easily missed.
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When a test is worth it
Persistent symptoms, malabsorption, an unusual diet, or a high-risk group — not as a routine check for well adults.
Why this guide matters
Simple advice, badly explained.
Vitamin D is one of the most oversold and most under-explained supplements in the UK. The three points below shape everything else on this page.
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Latitude, not lifestyle
Between October and March there is not enough UVB in UK sunlight to make vitamin D — however much you go outside.
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A cheap, boring supplement
A £5 bottle of D3 lasts a year. There is no upgrade that outperforms it.
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Testing is not routine
Well adults with no risk factors do not need a blood test — the winter dose is the answer.
The guidance in practice
From bottle to bloods — step by step.
The order the guidance runs in — from a simple winter dose, to correcting deficiency, to holding the level long-term.
Phase 1 · Baseline
Who should supplement, and when
Phase 2 · Correction
If a blood test shows deficiency
Phase 3 · Maintenance
Holding the level long-term
- 01
Baseline
Take 10 µg / 400 IU daily October–March
The UK Government recommendation for all adults through the darker months.
- 02
Baseline
Take year-round if higher-risk
Darker skin, housebound, always covered outdoors, pregnant or breastfeeding.
- 03
Correction
If deficient, use a loading course
Higher-dose regimens are specialist-directed and follow a blood test.
- 04
Correction
Take with a fat-containing meal
Vitamin D is fat-soluble — absorption improves with breakfast, not water alone.
- 05
Correction
Vitamin D3 preferred over D2
D3 (cholecalciferol) raises blood levels more reliably than D2.
- 06
Correction
Recheck bloods at 3 months
After a loading course, confirm the level has corrected before dropping to maintenance.
- 07
Maintenance
Continue a maintenance dose
Once corrected, most people stay on 10–25 µg daily to hold the level.
Typical timeline: 6–12 weeks from starting a loading course to a corrected blood level.
Signs of deficiency
What deficiency actually feels like.
None of these prove low vitamin D on their own — but a cluster in a higher-risk person is a strong reason to test.
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Bone pain
A deep, aching pain in the ribs, hips or long bones.
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Persistent fatigue
Tiredness that does not lift with sleep.
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Low mood
Often through the winter months, alongside other symptoms.
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Frequent infections
Repeated colds and chest infections may point to low levels.
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Muscle weakness
Difficulty rising from a chair or climbing stairs.
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Diffuse aches
A generalised “achy all over” feeling with no injury.
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Low sun exposure
Housebound, indoor worker, always covered, or shielding.
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Red flag: severe deficiency in a child — refer
Suspected rickets or a child with bone deformity needs paediatric review.
How to supplement
The eight practical decisions.
Dose, form, timing and when a blood test earns its place — the choices that make the guidance work in a real week.
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10 µg (400 IU) daily maintenance
The everyday adult dose — sufficient for most people from October to March.
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Loading course for deficiency
Higher-dose regimens (typically 6–10 weeks) directed by a clinician after a blood test.
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Year-round for higher-risk groups
Darker skin, veiled, housebound, pregnant or breastfeeding — supplement through summer too.
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Food-first approach
Oily fish twice a week, eggs and fortified spreads help — but rarely enough alone.
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Vitamin D test if symptomatic
A serum 25(OH)D level is the simple, definitive check when symptoms suggest deficiency.
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Vitamin D3 preferred
Cholecalciferol (D3) raises and holds blood levels better than ergocalciferol (D2).
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Take with a fatty meal
A small amount of dietary fat markedly improves absorption.
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Combined with adequate calcium
Bone health needs both — check calcium intake if bone symptoms are the concern.
What this guide is based on
The evidence behind every claim on this page.
UK Government, NHS and NICE guidance — current at the time of last review.
Key references
The guidance and reviews we relied on.
A quiet reminder
This guide is for information, not medical advice.
If you have persistent symptoms, are pregnant, or have a long-term condition, discuss your vitamin D with a clinician.
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Scientific Advisory Committee on Nutrition (SACN). Vitamin D and Health, 2016.
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NHS. Vitamin D — official patient guidance.
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National Institute for Health and Care Excellence (NICE). CKS: Vitamin D deficiency in adults.
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Royal Osteoporosis Society. Vitamin D and bone health guidance.
Red flags
When to seek specialist advice, not a supplement aisle.
For most people vitamin D is safe and simple. These are the situations where a clinician, not a blog post, is the right next step.
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Symptomatic deficiency in a child
Possible rickets — needs paediatric assessment, not a supplement bought online.
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Falls in older adults
Low vitamin D raises fall and fracture risk — check level and correct promptly.
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Malabsorption (coeliac, Crohn’s)
Absorption is reduced — higher doses under specialist care are often needed.
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Post-bariatric surgery
Lifelong monitoring — deficiency is common and dosing is specialist-led.
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Chronic kidney disease
Activation of vitamin D is impaired — an activated form may be required.
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Sarcoidosis and granulomatous disease
Supplementation can raise calcium unsafely — take only under specialist guidance.
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Very high doses without monitoring
Long-term intake above 100 µg (4,000 IU) risks hypercalcaemia — avoid without blood checks.
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Housebound patients
Care-home and shielding patients rarely get sufficient UV — supplement year-round.
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Ethnic-minority pregnant women
A group repeatedly flagged as high-risk — a full pregnancy dose is important.
Making it stick
A winter habit, not a health fad.
Four ideas that decide whether you actually take it, or whether the bottle sits at the back of a cupboard.
A quiet reminder
Boring, cheap and daily beats clever, expensive and forgotten.
A 10 µg tablet with breakfast, taken most days from October to March, is the whole intervention.
- 01 Habit
Take it with breakfast
Pair it with a fat-containing meal and it stops being a thing you forget.
- 02 Season
A winter routine, not a lifelong one
Most people only need it October to March — set a phone reminder for the clocks changing.
- 03 Family
Under-4s need it year-round
Children under 4 should have daily vitamin D drops all year (Healthy Start / NHS).
- 04 Testing
One test, not four
A single 25(OH)D level answers the question — routine repeat testing in well adults adds little.
Frequently asked
Everything we get asked about vitamin D.
Quick answers on dose, form, testing, safety and children — grounded in UK guidance.
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Do I really need a supplement in winter?
For most UK adults, yes — from October to March the sun is too weak at our latitude to make enough vitamin D, whatever the weather.
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How much should I take?
10 µg (400 IU) daily is the UK recommendation for adults and children over 4. Higher-risk groups should take it year-round.
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Is D3 better than D2?
Yes — vitamin D3 (cholecalciferol) raises and holds blood levels more reliably than D2 (ergocalciferol).
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Can I take too much?
Yes. Long-term daily intake above 100 µg (4,000 IU) without monitoring can raise blood calcium and harm the kidneys.
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Do I need a blood test?
Not for routine supplementation. A 25(OH)D test is worth doing if you have persistent symptoms, malabsorption, an unusual diet or you are in a high-risk group.
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What about vitamin D for children?
Under-4s should have daily vitamin D drops year-round (NHS Healthy Start advice). Children over 4 follow the adult guidance — 10 µg daily October to March.
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