Vitamin D3
Vitamin D3 in capsules, softgels, drops, oral sprays and D3-K2 combinations, from 400 IU up to high strength. We explain how D3 differs from D2, how oil aids absorption and which strength suits the winter months.Read more →
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Choosing a vitamin D3 supplement: forms, strengths and honest limits
Vitamin D3, or cholecalciferol, is the same form of vitamin D your skin makes from summer sunlight. It is fat-soluble, which means it needs a little fat in your gut to be absorbed properly. In the UK, sunlight from October to early March is too weak for your skin to make vitamin D, so this is the point in the year when most people start looking at a supplement.
Vitamin D contributes to the normal function of the immune system, to the maintenance of normal bones, teeth and muscle function, and to the normal absorption of calcium and phosphorus. Those are the effects European food law allows us to state, and we keep to them. You will find the wider range in our vitamins collection.
D3, D2 and why the carrier oil matters
D2 (ergocalciferol) comes from yeast and mushrooms. D3 comes from lanolin in sheep's wool or from lichen, a plant-like organism grown for vegan products. Research shows D3 raises vitamin D levels in the blood more reliably than D2, so D3 is what we stock as standard.
The second thing we check is what the D3 actually sits in:
- Softgels and capsules with oil: olive, sunflower or MCT oil, so you do not have to plan a fatty meal around them.
- Drops and oral sprays: easy to dose in small steps, practical for children and for anyone who dislikes swallowing capsules.
- Dry tablets and gummies: convenient, but take them with a meal that contains some fat.
Labels use both micrograms and international units, which causes a lot of confusion. 10 mcg is 400 IU, 25 mcg is 1,000 IU and 100 mcg is 4,000 IU. Doing that conversion is the quickest way to see whether a product marked high strength is really stronger than the one you already have at home.
How we choose vitamin D3
We look at three things: the form, the dose and the combinations. We stock cholecalciferol rather than D2, and we prefer products where the D3 is suspended in oil, because absorption is better that way. We carry 400 IU for a simple daily top-up and higher strengths up to 4,000 IU for people who get very little sun. Vegan D3 from lichen sits next to lanolin-based D3, so the choice stays yours. Every product passes our compliance team, we test products ourselves, and independent labs spot-check batches. You can read how we select brands and products.
Who this collection suits
Most people here are building a winter routine, roughly October to March. Others take D3 all year: if you spend your days indoors, cover your skin, or have darker skin, your body makes less vitamin D from sunlight. Babies and young children have their own drops in lower strengths. A blood test is the only way to know your own level, so without one it makes sense to stay inside the range public health advice sets.
Combination products are popular, and one deserves a word of caution. Formulas that pair D3 with vitamin K2 as MK-7 are not suitable for everyone: if you take warfarin or another vitamin K antagonist, speak to your GP or anticoagulation clinic before you start.
Many people also keep D3 next to a magnesium supplement in the same daily routine. Be realistic about the timeline: vitamin D builds up gradually in the blood, so think in terms of several weeks of consistent daily use, which is exactly why a dose you can keep up beats a dose you forget.
Frequently asked questions
Vitamin D3 is cholecalciferol, the form your skin produces from sunlight. It is also found in oily fish and egg yolks, and in supplements it comes from lanolin in sheep's wool or from lichen. Vitamin D2 is ergocalciferol, made from yeast or UV-treated mushrooms. Studies show D3 raises and maintains vitamin D levels in the blood more reliably than D2, which is why almost every supplement on the UK market, and everything in this collection, uses D3.
The NHS advice is a daily 10 microgram supplement for adults and children over one, including during pregnancy and breastfeeding, at least through autumn and winter. Babies have a slightly lower range. Many products contain more than 10 mcg, which is legal and common, but the official reference point is below.
| Group | Per day (mcg) | Per day (IU) |
|---|---|---|
| Babies, birth to 1 year | 8.5 to 10 | 340 to 400 |
| Children 1 to 4 years | 10 | 400 |
| Children over 4 and adults | 10 | 400 |
| Pregnant and breastfeeding | 10 | 400 |
There is no magic hour. Vitamin D3 is fat-soluble, so what matters is that some fat is present. Take it with your largest meal of the day, or choose a softgel or drop where the D3 is already dissolved in oil, and the timing becomes flexible. Consistency matters more than the clock: your blood level reflects your intake over weeks, not a single dose. Pick the moment you will actually remember, such as breakfast.
The strength is the same nutrient in every case, so choose on practicality and on whether fat is already included.
| Form | How it works | Suits |
|---|---|---|
| Softgel or oil capsule | D3 dissolved in oil | Daily use, no meal planning |
| Drops | Oil base, dose per drop | Children, fine adjustment |
| Oral spray | Absorbed in the mouth | Pill avoiders, travel |
| Tablet | Dry, no oil added | Take with a fatty meal |
| Gummy | Chewable, often flavoured | Poor swallowers, teens |
Both deliver cholecalciferol, so the molecule your body uses is identical. The difference is the raw material: lanolin from sheep's wool, or lichen grown and harvested for plant-based products. Lichen D3 is usually a little more expensive, because production yields are lower, and that price gap is honest rather than a mark-up. If you eat vegan, it is the option that genuinely fits you. If you do not, lanolin-based D3 in oil does the same job for less.
Combined D3 and K2 products are common, and both nutrients have their own approved role: vitamin D contributes to the maintenance of normal bones, and so does vitamin K. That is why shoppers with bone and joint goals often look at the combination. It is not compulsory, and vitamin K also comes from leafy greens. One caution: if you take warfarin or another vitamin K antagonist, do not start a K2 product without speaking to your GP or anticoagulation clinic.
Vitamin D accumulates gradually. Blood levels typically rise over several weeks of consistent daily intake, and how quickly depends on your starting level, your dose, your body weight and how much sun you get. That is the honest picture: this is a nutrient you top up steadily through the darker months, not something you feel within a day. The upside is that a modest daily dose taken every day works better than a large dose taken now and then.
Vitamin D is stored in the body, so more is not better. Taking very high amounts over a long period can raise blood calcium too far. EFSA has set tolerable upper intake levels that count everything together: food, fortified products and supplements. UK advice is not to exceed 100 mcg (4,000 IU) a day for adults without medical supervision.
| Age group | Upper level (mcg) | Upper level (IU) |
|---|---|---|
| Infants under 1 year | 25 | 1,000 |
| Children 1 to 10 years | 50 | 2,000 |
| 11 to 17 years | 100 | 4,000 |
| Adults, including pregnancy | 100 | 4,000 |
