Vitamin D2 or D3? The Difference Explained Simply

Anyone looking into vitamin D products quickly runs into two abbreviations: D2 and D3. The labels then show unwieldy names like "ergocalciferol" and "cholecalciferol," and the question soon comes up: is that the same thing? And if not – which form is the better choice? That's exactly what this guide is about. We explain what's behind the two forms, how they differ, and what that means in practical terms for choosing a product – including if you follow a vegan diet.

The short answer up front: both are genuine vitamin D. The key difference lies in their origin and in how reliably they raise vitamin D levels in the blood. But let's take this step by step.

What Is Vitamin D, Anyway?

Vitamin D isn't a single substance, but an umbrella term for a group of fat-soluble compounds. The two most important members for nutrition are vitamin D2 and vitamin D3. Both essentially perform the same job in the body – but they first have to be converted before they can.

Vitamin D holds a special position among vitamins: the body can produce it itself in the skin under the influence of sunlight. Strictly speaking, that's why it's more accurately described as a prohormone than a classic vitamin. During the darker months and with little time spent outdoors, however, the body's own production is often not enough – which is when diet and dietary supplements move into focus. And that's where the distinction between D2 and D3 becomes relevant.

Getting the framing right matters here: the recognized health claims apply to vitamin D in general – regardless of whether it's present as D2 or D3. So vitamin D contributes to the normal function of the immune system, it contributes to the maintenance of normal bones, and it contributes to normal muscle function. These functions are tied to the vitamin itself, not to a particular manufactured form.

Vitamin D2 (Ergocalciferol)

Vitamin D2's chemical name is ergocalciferol. It's formed in plants, yeasts, and fungi when their precursor (ergosterol) comes into contact with UV light. Mushrooms are a vivid example: when exposed to sunlight or targeted UV irradiation, they produce measurable amounts of vitamin D2.

Because D2 is of purely plant or fungal origin, it was long considered the quintessential "vegan" form of vitamin D. In practice, it's found in some fortified foods and in certain products. One drawback: D2 is considered somewhat less stable and is often described as less effective at raising and maintaining blood levels – more on that shortly.

Vitamin D3 (Cholecalciferol)

Vitamin D3 carries the name cholecalciferol. It's precisely the form our skin also produces itself under sun exposure. Through food, D3 is found mainly in animal sources: fatty saltwater fish like salmon or herring, cod liver oil, egg yolk, and in smaller amounts in dairy products.

Traditionally, D3 for supplements was obtained from animal raw materials – often from the wool grease (lanolin) of sheep. That's the reason many conventional D3 products aren't vegan. In the meantime, however, a plant-based alternative has emerged that delivers the same D3 form: vitamin D3 from lichen. We go into this in detail further below.

The Difference: Origin & Effectiveness

Let's sum up the two central differences.

1. Origin. Vitamin D2 comes from plants and fungi. Vitamin D3 comes from animal sources – or, in the modern vegan variant, from lichen. So if you look at origin alone, you might assume D2 is automatically the plant-based form and D3 the animal-based one. That rule of thumb no longer holds true today, because vegan D3 also exists.

2. Effectiveness at raising levels. This is where the most practically relevant difference lies. Both forms are converted into their active form in the body via the liver and kidneys. According to current expert assessment and the available research, however, vitamin D3 generally raises the so-called 25-OH vitamin D level in the blood more reliably and keeps it stable for longer than a comparable amount of D2. Put simply, the same amount of D3 often "moves the needle" more on the blood test. That's why D3 is the preferred form in nutritional counseling and in most products.

An important point for context: when it comes to stated amounts, the forms are on equal footing. In official reference values, 1 microgram of vitamin D is counted the same regardless of form, and the conversion is 1 microgram = 40 international units (IU). So a product with "20 µg (800 IU)" delivers the same declared amount whether it's D2 or D3 – it's only the biological utilization that tips in favor of D3.

What Does This Mean in Practice and When Buying?

For the vast majority of people reaching for a product, vitamin D3 is the obvious choice – simply because it raises levels more reliably. In drugstores and pharmacies, D3 is by far the more common variant anyway. You'll come across vitamin D2 less often, for example in certain specialty products or fortified foods.

When buying, it's worth looking at three things:

• Form: Does the label say "D3 / cholecalciferol" or "D2 / ergocalciferol"? For a reliable effect on blood levels, D3 is generally the better choice.
• Dosage: Check the figure given in micrograms and IU, and aim for typical, moderate amounts. Germany's Federal Institute for Risk Assessment considers a daily supplemental amount of up to around 20 µg (800 IU) well justifiable without a specific medical reason.
• Format: Because vitamin D is fat-soluble, oil-based drops or softgels are popular. You can read more about how the formats differ in our guide Capsule or softgel? The difference explained simply.

Vitamin D is often combined with vitamin K2. We explain why this combination is so often recommended in the article Vitamin D3 + K2: why the combination matters. And if you want to know what really matters when choosing a specific product, Which vitamin D product should you buy? can help.

Vegan: D3 from Lichen

For people who avoid animal products, this topic long sounded like a dilemma: the more effective form (D3) was animal-derived, while the plant-based form (D2) was considered less reliable. Vitamin D3 from lichen closes exactly this gap.

Lichens are a symbiosis of fungus and algae and produce – similar to animal sources – genuine cholecalciferol, meaning D3. The crucial point: chemically, this is the same D3 form as from the animal raw material, just obtained from a plant-based source instead. This makes it possible to combine the preferred D3 form with a purely plant-based origin.

So if you follow a vegan diet, you don't have to fall back on D2 – you can instead reach for a D3 product from lichen labeled as "vegan." Look for a corresponding note on the packaging, such as "vegan D3" or "D3 from lichen." We take a closer look at how plant-based sources fit into the bigger picture, using other nutrients as examples, among other places in the guide What are antioxidants? Explained simply.

Honestly Assessed

As clear as the trend toward D3 may be, a few things belong to an honest assessment. First: vitamin D2 is by no means "ineffective." It's genuine vitamin D and is likewise converted into its active form. The difference lies in how reliably and for how long it raises blood levels – not in a fundamental either-or.

Second: the best route to a good vitamin D supply doesn't necessarily run through a product. With enough time outdoors and moderate sun exposure to the skin, along with a balanced diet – say, with one to two servings of fatty saltwater fish per week – a good supply can often be achieved. A supplement is one building block, not an automatic necessity.

Third: more is not better. Vitamin D is fat-soluble and gets stored in the body; very high doses over a long period can harm health. For ongoing intake without a specific medical reason, moderate amounts are therefore advisable. Whether and at what level a supplement is right for you personally is best judged based on your individual vitamin D status – when in doubt, have it checked by a doctor.

Bottom line: D2 and D3 are both genuine vitamin D. For a product meant to reliably raise levels, D3 is generally the better choice – and thanks to lichen, it's now also available in a purely plant-based form. If you want to dig deeper into related vitamins, you'll find further background in our guides to Vitamin K: blood clotting, bones & K2 and Vitamin E: the fat-soluble antioxidant.

Frequently Asked Questions (FAQ)

Is Vitamin D3 Fundamentally Better Than D2?

Both are genuine vitamin D and are converted into their active form in the body. According to current expert assessment, however, vitamin D3 usually raises blood vitamin D levels more reliably and keeps them stable for longer than the same amount of D2. That's why D3 is the preferred form in practice.

Is Vitamin D2 Always Vegan and D3 Always Animal-Derived?

This rule of thumb no longer holds true today. D2 comes from plants and fungi. D3 was traditionally obtained from animal sources (such as wool grease), but is now also available as vegan D3 from lichen. So if you live vegan, you can reach for lichen-derived D3 and don't have to fall back on D2.

What Do the Figures µg and IU on the Packaging Mean?

µg stands for micrograms, IU for international units. Both describe the same amount, just in different units. The conversion is 1 µg = 40 IU. So a product with "20 µg" corresponds to "800 IU" – regardless of whether it's D2 or D3.

Can I Cover My Vitamin D Needs Through Sunlight Alone?

The body produces vitamin D itself in the skin under sun exposure, and with enough time spent outdoors, a good supply can often be achieved. During the darker months and with little time spent outside, however, the body's own production can be lower. In that case, diet and, if needed, a supplement can help.

What Is Vitamin D Important for in the Body?

Its recognized functions are: vitamin D contributes to the normal function of the immune system, it contributes to the maintenance of normal bones, and it contributes to normal muscle function. These claims apply to vitamin D in general – that is, to both D2 and D3.