Vitamin D comes in two main forms, D2 and D3. Both can raise your vitamin D levels, but they come from different sources and the body does not handle them identically. Here is how they differ, what the trials show, and how to choose between them, including if you are vegan.
What is vitamin D2?
Vitamin D2, or ergocalciferol, is made by fungi such as yeast and mushrooms when they are exposed to ultraviolet light. Supplement makers produce it by irradiating ergosterol from yeast, which makes D2 vegan. You will find it in UV-exposed mushrooms, in some fortified foods such as plant milks and cereals, and in some supplements. Your body does not make D2 itself.
What is vitamin D3?
Vitamin D3, or cholecalciferol, is the form your skin makes when UVB light hits it, and the form found in fatty fish and egg yolks. Most D3 supplements are made from lanolin, the oil in sheep's wool, so they are not vegan. D3 can also be made from lichen, a partnership between a fungus and algae, which is suitable for vegans; we explain more in what is lichen.
Both forms need activating
Neither D2 nor D3 does anything until your body converts it. Your liver turns both into 25-hydroxyvitamin D, the form a blood test measures, and your kidneys turn that into the active hormone, 1,25-dihydroxyvitamin D. So D3 is not the 'active' form; it is simply the form your body makes naturally.
Is vitamin D3 better than D2?
For raising and maintaining blood levels, the evidence generally favors D3:
- A meta-analysis of randomized trials found that D3 raised blood levels of 25-hydroxyvitamin D more than D2. The gap was clearest with large, infrequent doses and smaller with daily dosing.
- In a 12-week winter trial at the University of Surrey, the same daily amount in fortified food raised blood levels more as D3 than as D2.
- In a 12-week trial, D3 was about 87% more potent than D2 at raising and maintaining blood levels and led to two to three times more storage in the body.
- In a winter trial, D3 was better at maintaining levels over the winter months, and another trial found that taking D2 lowered blood levels of D3, which helps explain the difference.
D2 is not useless: it does raise vitamin D levels, and for vegans who prefer it, a D2-fortified food or supplement is still a real source. But if you are choosing a supplement, D3 is the more reliable option.
Which form should you choose?
- For most people: vitamin D3, at a dose that meets your needs without going over the upper limit.
- If you are vegan or vegetarian: look for D3 from lichen, or use D2 if you prefer. Check the label, because most D3 is from lanolin. Our article on why to take vegan vitamin D compares the two sources.
- Whichever you choose: take it with a meal that contains some fat and take it consistently.
How much vitamin D do you need?
The RDA is 600 IU (15 mcg) a day for ages 1 to 70 and 800 IU (20 mcg) after 70, with an upper limit of 4,000 IU (100 mcg) a day for adults. Sun and food count toward that total; our guides to sources of vitamin D and how much vitamin D you need go into detail.
Our Sol Food tablets provide 2,000 IU of vitamin D3 from lichen in one small organic, vegan tablet, above the RDA and within the upper limit. If you are pregnant, have kidney disease or take prescription medicines, check with your doctor before starting a vitamin D supplement.
