Vitamin D3 4000IU — Winter Immunity Dose
4000 IU vitamin D3 — the correction dose recommended by many NHS clinicians for deficient UK adults during winter months.
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Less than a coffee top-up. Optimal nutrition for 25p/day — the most cost-effective investment in your health.
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Supply size
Most customers reorder this monthly. Each pack lasts ~30 days.
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£0.50
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£3.50
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£14.99
per month
Less than a daily coffee — for daily nutritional support from Vitamin D3.
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📦 What to expect when it arrives
Premium box
Double-sealed. No cheap poly bags — every Medibro order ships in a quality box.
Amber glass
UV-protective amber glass preserves potency. Satisfying click-lid seal.
Little extras
Every first order includes a usage guide and a surprise freebie — see what you get.
Start today
Take your first dose the day it arrives — don't wait for a 'perfect moment'.
Your 30-day journey starts today
Future you will look back on this moment.
Based on typical customer reports. Individual results vary. Backed by our 30-day guarantee.
Premium packaging, inside and out
Amber glass jar
Blocks UV degradation, no plastic leaching
100% recyclable
Jar, cap, and box are fully kerbside recyclable
No artificial fillers
No magnesium stearate, silicon dioxide, or titanium dioxide
- Free UK delivery over £35
- 14-day hassle-free returns
- Secure checkout, audit-logged
- Manually compliance-reviewed
Order dispatched, tracking info sent. Most customers take their first dose the day it arrives.
Research shows it takes ~14 days to anchor a new habit. By now, most customers have found their ideal time of day.
At 8 weeks, customers report the strongest improvements. Consistency is everything with nutritional supplements.
Over 90% of Medibro subscribers are still on the same product at 3 months — the clearest signal a supplement is working.
The UK's October–March sunshine gap means virtually all UK adults have insufficient vitamin D from October to March. For those with confirmed deficiency or who are at high risk (dark skin, over 65, indoor workers), 4000 IU is the commonly recommended correction dose.
Contains no unnecessary additives — just D3 in olive oil inside a bovine softgel.
Benefits
- ✓Immune function
- ✓Bone health
- ✓Mood
- ✓Muscle function
- ✓Deficiency correction
Dosing Guide
How to take Vitamin D3 4000IU — Winter Immunity Dose
Take 1 softgel daily with food. For correction of deficiency: use for 3 months then test 25(OH)D levels. For maintenance: switch to 1000–2000 IU.
Always read the label. Consult a healthcare professional if you have any medical conditions or take prescription medication.
Quality & transparency
Why form matters
Medibro uses
D3 + K2 (MK-7 form)
Long-acting MK-7
Others often use
D3 alone or K2 as MK-4
Lower bioavailability
MK-7 has a 72-hour half-life vs. MK-4's 1-hour — meaning it's active in your system all week.
K2 directs calcium to bones rather than arteries. Without K2, high-dose D3 can lead to soft-tissue calcium deposits. MK-7 is the clinically preferred form.
How we compare
Medibro vs. typical high-street / marketplace alternatives
| Feature | Medibro | Others |
|---|---|---|
| Form | D3 + K2 (MK-7) | D3 alone |
| IU per capsule | 4000 IU | 1000 IU |
| K2 for calcium routing | ||
| Olive oil base (fat-soluble) | ||
| Third-party tested | ||
| 30-day guarantee |
NHS recommends vitamin D supplementation
The NHS advises everyone in the UK to consider taking 10mcg vitamin D daily, especially from October to March when sunlight is insufficient.
Source: NHS.uk — Vitamin D
Vitamin D3 is more effective with:
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Your personalised stack
Recommended to pair with Vitamin D3
What to expect over time
Blood serum vitamin D starts climbing. Most people don't notice changes yet — this is normal.
Serotonin synthesis improves with adequate D3. Many users notice improved mood and reduced fatigue.
T-cell activation is D3-dependent. Cold and flu resilience measurably improves.
Bone density, cardiovascular and cognitive benefits accumulate. Annual blood test should show 75–200 nmol/L.
What to expect
A realistic week-by-week guide for first-time users
Blood levels starting to rise. You won't feel anything yet but the deficit is closing.
Serotonin regulation improves as D3 levels normalise. Mood often brightens noticeably.
Full immune priming and bone-density support established. Carry on through winter.
Continued daily use keeps blood levels optimal. Do not stop mid-winter.
Individual results vary. Consistency is key — don't assess before week 6.
Clinical evidence
Peer-reviewed research⏰ How to take for best results
Best time
Morning, with breakfast
Take with
Fat-containing meal — D3 is fat-soluble
Avoid with
Calcium supplements at same time (separate by 4 hours)
K2 (included) directs calcium to bones, not arteries. Essential when taking high-dose D3.
Personalised dose calculator
For guidance only. Consult your pharmacist or GP if you take prescription medication.
Frequently asked questions
Pairs perfectly with
15% off when bought togetherOmega-3 High Strength
Fat-soluble booster
Vitamin D3 is fat-soluble — taking with omega-3 can improve absorption by up to 50%
Bundle total: £39.98 → £33.98
Find your perfect supplement stack
Answer 4 quick questions and get a personalised stack built around your goals, health history, and lifestyle.
Medibro Quality Score™
Independent assessmentPurity
97
Overall
out of 100
Potency
Value
How we compare
Medibro | Budget | Pharmacy | |
|---|---|---|---|
3rd-party COA testing | |||
Premium forms (glycinate, KSM-66, TG omega) | |||
Full ingredient transparency | |||
UK pharmacist reviewed | |||
No proprietary blends | |||
30-day money-back guarantee | |||
Eco-friendly packaging |
Comparison reflects general market observations. Specific brands may vary.
What outcomes matter most to you?
🌍 Ingredient sourcing
Cholecalciferol (D3)
Norway
Lichen-derived, vegan-certified
Menaquinone-7 (K2)
Japan
MK-7 from natto fermentation
UK deficiency data
1 in 5 UK adults are vitamin D deficient — rising to 1 in 3 in winter months
Source: NHS / SACN 2016
Common symptoms
Higher risk if
This information is educational. Always consult your GP before supplementing if you have a health condition.
Founded by a UK pharmacist
“After 12 years dispensing prescriptions, I was frustrated by the gap between expensive supplements and what the evidence actually supports. Medibro was built to source properly — clinical doses, verified purity, fair prices.”
— MPharm, GPhC registered · Medibro founder
Every formula is reviewed by our in-house pharmacy team before launch.
Supplement Interactions
What can I safely combine this with?
K2 directs calcium (mobilised by Vitamin D) to bones and away from arteries. D3+K2 is the gold standard combination.
View Vitamin K2 →Magnesium activates Vitamin D. Most people are deficient in both — supplementing together dramatically improves Vitamin D efficacy.
Omega-3 enhances Vitamin D receptor sensitivity, making the same dose of D3 more effective.
⚕️ Always consult a healthcare professional before combining supplements with medication.
Stack Synergies
Science-backed pairings for better results
Required to activate Vitamin D — without it, up to 50% of D3 stays inactive in the body
Directs calcium deposited by D3 to bones rather than arteries — essential pairing
Fat-soluble co-absorption; omega-3 enhances D3 bioavailability and anti-inflammatory action
Synergies based on published nutritional science. Individual results may vary. Always consult a healthcare professional before combining supplements.
Complete your stack
✨What customers say
From 20 reviews★ 4.8Customers appreciate the high dose of 4000 IU in a convenient small capsule, which is effective for improving mood, energy levels, and overall health, especially during winter months.
Some users noted that the product may not be suitable for those who prefer lower doses or have specific dietary restrictions, as it is oil-based.
This product is ideal for UK residents, particularly those with a diagnosed vitamin D deficiency, athletes, and individuals seeking to improve their immune function during winter.
Customer reviews
- ★★★★★Sarah M.01/05/2026D3 at the right dose
The 400 IU the NHS recommends is a minimum. For actual repletion after deficiency, 4,000 IU is appropriate.
- ★★★★★Isla P.24/04/2026Convenient high dose capsule
One small capsule covers a full therapeutic dose. Very convenient for winter supplementation.
- ★★★★★Sarah M.23/04/2026Convenient high dose capsule
One small capsule covers a full therapeutic dose. Very convenient for winter supplementation.
- ★★★★☆Freya Z.13/04/2026Good oil-based D3 for absorption
Oil-based D3 has superior absorption to dry powder forms. This product absorbs well and my levels have improved.
- ★★★★★Alfie B.28/03/2026Doctor-recommended dose for winter
My GP suggested 2,000-4,000 IU during winter. This product delivers the higher dose which my blood test confirmed I needed.
- ★★★★★Freya Z.24/03/2026Doctor-recommended dose for winter
My GP suggested 2,000-4,000 IU during winter. This product delivers the higher dose which my blood test confirmed I needed.
- ★★★★☆Lily D.19/03/2026Good oil-based D3 for absorption
Oil-based D3 has superior absorption to dry powder forms. This product absorbs well and my levels have improved.
- ★★★★★Emma W.02/03/2026D3 at the right dose
The 400 IU the NHS recommends is a minimum. For actual repletion after deficiency, 4,000 IU is appropriate.
- ★★★★★Grace S.01/03/2026D3 at the right dose
The 400 IU the NHS recommends is a minimum. For actual repletion after deficiency, 4,000 IU is appropriate.
- ★★★★★Mark W.Verified buyer28/02/2026Winter depression gone
Severe seasonal affective disorder every winter. Psychiatrist suggested 4000IU D3 alongside my regular treatment. This winter was transformatively different — mood stable, energy maintained, the usual January depression absent. Blood test confirmed optimal D3 levels.
- ★★★★★Emma W.24/02/2026Doctor-recommended dose for winter
My GP suggested 2,000-4,000 IU during winter. This product delivers the higher dose which my blood test confirmed I needed.
- ★★★★★Chloe V.13/02/2026Convenient high dose capsule
One small capsule covers a full therapeutic dose. Very convenient for winter supplementation.
- ★★★★★Charlie D.12/02/2026D3 at the right dose
The 400 IU the NHS recommends is a minimum. For actual repletion after deficiency, 4,000 IU is appropriate.
- ★★★★☆Emma W.07/02/2026Good oil-based D3 for absorption
Oil-based D3 has superior absorption to dry powder forms. This product absorbs well and my levels have improved.
- ★★★★★Alfie B.17/01/2026Convenient high dose capsule
One small capsule covers a full therapeutic dose. Very convenient for winter supplementation.
- ★★★★★Susan H.Verified buyer13/01/2026GP recommends this dose
My GP specifically recommends 4000IU for patients with established D3 deficiency. Most standard supplements are 400-1000IU which barely maintains levels. 4000IU actually raises and maintains optimal blood levels. This is the right dose for correction.
- ★★★★★Mia J.12/01/2026Doctor-recommended dose for winter
My GP suggested 2,000-4,000 IU during winter. This product delivers the higher dose which my blood test confirmed I needed.
- ★★★★☆John K.31/10/2025Sports performance improved
Athletes are at high risk of D3 deficiency due to indoor training. Added 4000IU in winter when outdoor sun exposure is minimal. Training recovery and muscle function measurably improved. Blood test confirmed levels raised to optimal.
- ★★★★☆Paul M.Verified buyer19/10/2025Immune function completely different
Used to get 4-5 illnesses per winter. First winter on 4000IU: one mild cold in January. Vitamin D is practically a hormone for the immune system. The higher corrective dose makes all the difference.
- ★★★★★Helen D.Verified buyer25/08/2025Essential for UK residents with deficiency
Deficiency confirmed on blood test at 12 nmol/L (severely low). GP recommended high-dose correction before maintenance. 4000IU for 3 months, now at 95 nmol/L (optimal). Energy, mood, and immune function transformed.
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