There are two main types of vitamin D that matter for your health: vitamin D2 and vitamin D3. While scientists have identified five numbered forms (D1 through D5), only D2 and D3 occur naturally in meaningful amounts, and these are the only two used in foods, supplements, and prescriptions. They share the same basic function, helping your body absorb calcium and support bone health, but they come from different sources and differ in how effectively they raise your blood levels.
Vitamin D2 vs. Vitamin D3
Vitamin D2 (ergocalciferol) comes from plants and fungi. It’s derived from ergosterol, a compound produced by mushrooms and yeast. Vitamin D3 (cholecalciferol) comes from animal sources and is also the form your skin produces when exposed to sunlight. The chemical difference between them is small but meaningful: their side chains are slightly different, with D2 carrying an extra methyl group and a double bond that D3 lacks.
Both forms follow the same metabolic pathway once inside your body. Your liver converts whichever type you consume into a circulating form, and your kidneys then convert that into the active hormone your cells actually use. Despite sharing this pathway, the two forms are not equally potent.
Which Type Raises Blood Levels More
Vitamin D3 is generally more effective at raising and maintaining your blood levels of vitamin D. A 2024 meta-analysis of 20 clinical studies found that D3 consistently produces a higher increase in blood vitamin D levels compared to D2 when taken as a daily supplement. Interestingly, this advantage disappears in people with a BMI above 25 (the typical threshold for overweight). In those individuals, D2 and D3 performed similarly, suggesting that excess body fat may blunt D3’s potency edge.
There’s also a third compound worth knowing about: 25-hydroxyvitamin D3, a pre-activated form that’s been used in clinical studies. It’s estimated to be three to five times as potent as standard D3, though it’s not widely available as a consumer supplement.
Where Each Type Comes From
Your body makes vitamin D3 in the skin when UVB radiation in the 295 to 315 nanometer wavelength range hits a cholesterol compound called 7-dehydrocholesterol. Sunlight is the primary source of vitamin D for most people worldwide, though season, latitude, skin tone, and sunscreen use all affect how much you produce.
In food, vitamin D3 occurs naturally in fatty fish, fish liver oils, beef liver, egg yolks, and cheese. Vitamin D2 is found in mushrooms, especially those treated with UV light to boost their levels. The FDA has approved UV-treated mushroom powder as a food additive specifically to increase vitamin D2 content in packaged foods.
Supplement Sources and Vegan Options
Most vitamin D supplements on store shelves contain D3, which is typically produced by irradiating lanolin, a waxy substance from sheep’s wool. Vitamin D2 supplements are manufactured by exposing ergosterol from yeast to UV light. Because D2 comes from fungi, it has traditionally been the go-to form for vegans.
That’s changing, though. An animal-free version of D3 sourced from lichen is now available, giving people who avoid animal products access to the more potent form. If sourcing matters to you, it’s worth checking with the manufacturer, since labels don’t always specify whether D3 comes from lanolin or lichen.
How Your Body Activates Vitamin D
Whether you swallow a D2 capsule, eat salmon rich in D3, or synthesize D3 in your skin, the vitamin isn’t immediately useful. It has to go through two conversion steps before your cells can use it.
First, your liver uses an enzyme called CYP2R1 to convert vitamin D into 25-hydroxyvitamin D. This is the form measured in a standard blood test, and it’s the best indicator of your overall vitamin D status. Second, your kidneys convert that intermediate into 1,25-dihydroxyvitamin D, the fully active hormone. This final step uses an enzyme called 1-alpha-hydroxylase, which sits inside kidney cells. Because both the liver and kidneys play essential roles, people with liver disease or kidney disease are at higher risk of vitamin D deficiency even if their intake or sun exposure seems adequate.
Food Sources at a Glance
- Vitamin D3 foods: salmon, mackerel, sardines, cod liver oil, beef liver, egg yolks, cheese
- Vitamin D2 foods: UV-treated mushrooms (maitake, portobello, shiitake), fortified foods using mushroom powder
- Fortified products: milk, orange juice, and cereals may contain either D2 or D3 depending on the brand
Mushrooms are unique in the plant world because they can generate vitamin D2 when exposed to sunlight or UV lamps, much like human skin generates D3. Some grocery stores sell mushrooms specifically labeled as high in vitamin D, meaning they’ve been UV-treated after harvest. The amount of D2 in untreated mushrooms varies widely and is often low.
The Bottom Line on Types
For practical purposes, you’re choosing between two forms: D2 and D3. Both work. Both follow the same activation pathway. D3 is more effective at raising blood levels for most people at a healthy weight, and it’s the form your body naturally produces from sunlight. D2 remains a solid plant-based option, particularly for those who prefer a supplement without animal-derived ingredients, though lichen-sourced D3 now fills that gap too.