Supplement Guide · Vitamin D
Vitamin D: The One Supplement Most Brits Should Consider
Vitamin D is the one supplement with a genuinely strong case for most people living in the UK. Our latitude means there is not enough sunlight from about October to March for the skin to make adequate vitamin D, and deficiency is common. It supports bone health, immune function and muscle, which is why public health bodies advise considering it over winter.
The UK guidance is around 400iu (10 micrograms) a day as a minimum to maintain levels, but many people, particularly those with darker skin, limited sun exposure or who cover up, benefit from more. A common effective range is 1000–4000iu daily. Staying at or below 4000iu keeps you within the recognised safe upper limit for unsupervised use.
Vitamin D3 (cholecalciferol) is the preferred form, as it raises blood levels more effectively than D2. Because vitamin D is fat-soluble, it is best taken with a meal containing some fat for absorption. A daily dose is more sensible than occasional large boluses for most people.
Many products pair D3 with vitamin K2 (MK-7), and there is a reasonable rationale: K2 helps direct calcium into bone rather than soft tissue, so the two work well together. It is a sensible combination rather than an essential one, and a plain, well-dosed D3 is still an excellent buy.
More is not automatically better, and very high doses without monitoring can cause problems by raising calcium too far. If you suspect significant deficiency, or want to go beyond the everyday range, a simple blood test guides the right dose. Our scores reward honest, well-dosed D3 (and sensible D3 plus K2) products over underdosed or overpriced ones.
Top Vitamin D picks
Ranked by The Lifting Lab Effectiveness Match score.
Frequently asked
How much vitamin D should I take?
At least 400iu daily to maintain levels, with many UK adults benefiting from 1000 to 4000iu, especially in winter. Staying at or below 4000iu keeps within the safe upper limit for unsupervised use.
Is D3 better than D2?
Yes. Vitamin D3 (cholecalciferol) raises and maintains blood levels more effectively than D2, so it is the preferred form.
Should vitamin D be taken with K2?
It is a sensible pairing, as K2 helps direct calcium into bone, but it is not essential. A well-dosed plain D3 is still very effective.
References
Sources behind this guide. Each was checked against the original publication.
- 1.NHS. Vitamins and minerals — Vitamin D. National Health Service (UK). View source
- 2.van den Heuvel EGHM, et al. (2024). Comparison of the effect of daily vitamin D2 and vitamin D3 supplementation on serum 25-hydroxyvitamin D concentration: a systematic review and meta-analysis. Adv Nutr 15(1):100133. View source
- 3.Alnafisah RY, et al. (2024). The impact and efficacy of vitamin D fortification. Nutrients 16(24):4322. View source
This guide is educational and not medical advice. For personal health concerns, or before starting any supplement that could affect a medical condition or medication, speak to a qualified clinician.