If you've ever picked up a bottle of vitamin D and noticed it says "D3" or "D2" on the label, you've probably wondered whether it actually matters. They're both vitamin D, right?
Yes, but they're not identical. And depending on your diet, lifestyle, and health goals, the form you choose can make a difference in how well your body uses it.
What Are Vitamin D2 and D3?
"Vitamin D" is really a category, not a single molecule. The two main forms are:
Vitamin D2 (ergocalciferol) comes from plants and fungi. It's produced when a compound called ergosterol in plants is exposed to UV light. Mushrooms are one of the few natural food sources of D2, and it's also the form most commonly used to fortify foods like cereals, orange juice, and some plant-based milks.
Vitamin D3 (cholecalciferol) comes from animal sources and is also the form your skin produces when exposed to sunlight. You'll find it naturally in fatty fish like salmon and trout, egg yolks, and beef liver. Most vitamin D supplements on the market today use D3.
Both forms are fat-soluble, which means your body absorbs them best when taken alongside a meal that contains some fat. And both go through the same basic activation process: your liver converts them into calcidiol (the form measured in blood tests), and then your kidneys convert that into calcitriol, the active hormone your body actually uses.
So if they follow the same pathway, does it matter which one you take?
D3 Raises Blood Levels More Effectively
This is where the research is fairly clear. While both D2 and D3 can raise your vitamin D levels, D3 does it better.
A systematic review and meta-analysis of randomized controlled trials found that D3 supplementation raised serum 25(OH)D levels significantly more than D2. Some individual studies have shown D3 to be roughly twice as effective at raising blood levels when given as a single dose. The difference appears to come down to how the liver processes each form. D3 seems to be the preferred substrate for the liver enzyme that handles conversion, and it also stays active in the body longer before being broken down.
In practical terms, this means that if two people take the same dose of vitamin D, the person taking D3 is likely to end up with higher blood levels than the person taking D2.
Where Each Form Shows Up
Here's a quick breakdown of where you'll typically find D2 and D3:
| Vitamin D2 | Vitamin D3 | |
|---|---|---|
| Source | Plants, fungi | Animals, sunlight |
| Found naturally in | UV-exposed mushrooms, yeast | Fatty fish, egg yolks, liver |
| Common in fortified foods | Cereals, orange juice, some plant milks | Cow's milk (in Canada), margarine |
| Supplement form | Less common | Most common |
| Vegan-friendly | Yes (always plant-derived) | Sometimes (can be derived from lichen) |
| Effectiveness at raising blood levels | Moderate | Higher |
So Which Should You Take?
For most people, D3 is the better choice. It raises blood levels more effectively, stays in the body longer, and is the form your body naturally produces from sunlight. It's also the form used in the majority of high-quality supplements and the one most often recommended by healthcare practitioners.
If you follow a vegan or plant-based diet, D3 can still work for you. Traditionally, D3 was sourced exclusively from animal products like lanolin (sheep's wool oil). But today, vegan D3 supplements derived from lichen are widely available and offer the same effectiveness as animal-sourced D3. If you're exploring different supplement formats, you'll find vegan options in drops, capsules, and softgels.
If you've been prescribed high-dose vitamin D by a doctor, it's worth noting that prescription vitamin D is sometimes D2 (ergocalciferol), particularly in certain countries. This doesn't mean D2 is bad. It still works. But for everyday over-the-counter supplementation, D3 is generally the stronger option.
What About Food Sources?
Most foods that naturally contain vitamin D provide D3. Salmon, trout, sardines, and egg yolks are all D3 sources. The exception is mushrooms, especially those exposed to UV light during growing, which provide D2.
Fortified foods are a mix. In Canada, cow's milk and margarine must be fortified with vitamin D by law, and these typically use D3. Plant-based milks and cereals often use D2, though this varies by brand, so checking the label is always a good idea.
Either way, food alone usually doesn't cover the full daily requirement for most Canadians, which is why supplementation plays such an important role.
Does the Form Matter as Much as Consistency?
Here's the honest answer: the difference between D2 and D3 matters, but not as much as simply taking vitamin D regularly and at the right dose.
A person who takes D2 every day with food is still going to be in much better shape than someone who takes D3 sporadically or on an empty stomach. Consistency and timing make a bigger difference than most people realize, and pairing vitamin D with the right supporting nutrients like magnesium and K2 matters even more.
That said, if you're choosing between the two and everything else is equal, D3 is the stronger pick.
The Bottom Line
Vitamin D2 and D3 both contribute to your vitamin D levels, but D3 is more effective at raising and maintaining those levels over time. It's the form your body makes from sunlight, the form found in most animal-based foods, and the form recommended by most health professionals for daily supplementation.
Whether you're just starting out with vitamin D or looking to fine-tune your routine, choosing D3 in a format you'll actually take every day is one of the simplest ways to support your long-term health. If you're new to all of this, our complete guide to vitamin D is a good place to start.
