Due in stock end of October 2026. Pre-order now and we'll dispatch as soon as it arrives.
Why Take Vitamin D?
Dr Marks Vitamin D3 4000IU pairs a high-strength dose of D3 with Vitamin K2 — vitamin D and vitamin K both contribute to the maintenance of normal bones.
Why add K2?
Vitamin D contributes to the normal absorption and utilisation of calcium, and vitamin K contributes to the maintenance of normal bones. We include 100µg of vitamin K2 as menaquinone-7 (MK-7) in every capsule.
Key Benefits
- Bone & Teeth Support — Vitamin D contributes to the maintenance of normal bones and teeth; vitamin K contributes to the maintenance of normal bones
- Immune System — Vitamin D contributes to the normal function of the immune system
- Muscle Function — Vitamin D contributes to the maintenance of normal muscle function
- Calcium & Phosphorus Absorption — Vitamin D contributes to normal absorption/utilisation of calcium and phosphorus, and normal blood calcium levels
- Blood Clotting — Vitamin K contributes to normal blood clotting
Why Dr Marks?
Ours provides 100µg (4,000 IU) vitamin D3 with 100µg vitamin K2 (MK-7). 100µg is the maximum daily amount of vitamin D for adults. It's formulated by GPs.
Directions
Take one capsule daily with food. 60 capsules per pouch. Suitable for adults. Contains vitamin K. If you take anticoagulant medicine such as warfarin, speak to your GP or pharmacist before taking this product. Speak to your GP or pharmacist before use if you have a condition affecting calcium levels (such as hyperparathyroidism, sarcoidosis or kidney stones), if you take thiazide diuretics (water tablets) or digoxin, or if you are pregnant or breastfeeding.
Do not take alongside other vitamin D supplements or multivitamins containing vitamin D. 100µg (4,000 IU) is the maximum daily amount of vitamin D for adults.
Formulation Comparison
Dr Marks Vitamin D3 4,000 IU + K2 vs Typical High-Street Supplement
60 vegetarian capsules · 1 a day · 25p/daySuitable for vegetarians
| What to look for | Dr Marks Vitamin D3 4,000 IU + K2 | Typical High-Street Supplement |
|---|---|---|
| D3 + K2 pairing | Dr MarksMaximum adult daily D3 (4,000 IU / 100µg) paired with 100µg Vitamin K2 (MK-7) |
Typical High-StreetD3-only tablets with no Vitamin K2 |
| K2 form & dose | Dr Marks100µg all-trans MK-7 (menaquinone-7, 133% NRV) |
Typical High-StreetShort-acting MK-4 or token 15–25µg K2 doses |
| Capsule & carrier | Dr MarksVegetarian HPMC capsule with MCT coconut oil powder (no seed-oil softgels) |
Typical High-StreetSunflower/soybean oil softgels or compressed tablets |
| Excipients & coatings | Dr MarksNo titanium dioxide, talc, tablet glazes or artificial colours |
Typical High-StreetBulking agents, tablet glazes and artificial colours |
| Format & packaging | Dr MarksFlat, letterbox-friendly resealable pouch |
Typical High-StreetBulky plastic tubs or blister packs |
| Formulated by | Dr MarksPractising UK GPs |
Typical High-StreetGeneric mass-market contract formulas |
Compared against common single-form or standard A–Z high-street tablet formulations.
A GP’s View on Supplement Timelines
Consistent Daily Use: What Happens in the Body
Many supplement brands print fixed charts promising you will “feel more energy in Week 2” or “see thicker hair in Month 2”. As practising UK GPs, we won’t do that. What happens when you take a supplement depends on whether you are topping up an everyday diet (where nutrients work quietly in the background and you may not “feel” a sudden change) or correcting a low level found on a GP blood test.
Days 1–7
Daily routine & digestive comfort
Take 1 capsule a day with a main meal and water. Taking your capsule with food is gentler on the stomach and helps fat-soluble vitamins absorb normally.
Weeks 2–6
Steady daily nutritional intake
Consistent daily intake helps top up your diet every day rather than in sporadic bursts. Water-soluble nutrients (such as B vitamins and vitamin C) are used daily and aren’t stored in large amounts, while fat-soluble nutrients (such as vitamin D) build up gradually with steady daily intake.
Weeks 8–12 (1–2 pouches)
Long-term maintenance & GP blood re-checks
Red blood cells turn over roughly every 90 to 120 days. When a GP treats a confirmed low level (such as vitamin B12 or vitamin D), NICE and NHS guidance typically schedules a clinical review or follow-up check around 3 months. For everyday dietary top-ups, steady ongoing habits matter most.
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Dr Marc CrutchleyMBChB MRCGP MSc BSc (Hons), Co-founder
Dr Mark WilshereMBChB MRCGP DCH BSc (Hons), Co-founder
GP-Formulated in the UK✓ GMC-Registered Practising UK GPs · 40+ Years Combined Experience
Meet the GPs behind Dr Marks
Formulated by Dr Marc Crutchley and Dr Mark Wilshere, practising UK GPs.
With over 40 years of combined clinical experience as GMC-registered UK GPs, we formulate every Dr Marks supplement using bioavailable nutrient forms at meaningful daily doses — in clean plant-based capsules with zero synthetic fillers or binders.
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