Breaking Down Vitamin D, D2 and D3

Vitamin D is an umbrella term for both D2 and D3 — both help keep your bones and immune system strong

If you’re in the market for a vitamin D supplement, you might have come across bottles labeled as vitamin D3. Is that what you need? What is vitamin D vs. vitamin D3?

But wait, there’s more?! Vitamin D...2? What’s that about?

Confused? No need to be. Family medicine specialist Matthew Goldman, MD, shares the similarities and differences between vitamin D, D2 and D3.

Vitamin D vs. D3 vs. D2

We typically think of vitamin D as one thing. But in reality, vitamin D is a category. Vitamins D2 and D3 are the two main forms within the category.

Think of it like this: We can say “car” to mean anything from a two-door convertible to a three-row SUV. They’re all cars — four wheels, engines, seats, etc. — but they serve different needs. Vitamin D is the car, D2 and D3 are the types of car.

And, in case you’re curious, there’s no vitamin D1. At least not anymore.

“Scientists originally found a compound they named vitamin D1. But it turned out to actually be vitamin D2 mixed with other substances,” Dr. Goldman notes. (Fascinating tidbit for your next cocktail party icebreaker, eh?)

So, sticking with vitamins D2 and D3 — what are the similarities? The differences? And which is right for you? Let’s take a closer look to find out.

Vitamin D2 and D3 similarities

There’s good reason both D2 and D3 are considered vitamin D.

They’re both fat-soluble vitamins, which means they get absorbed into your body with the fats you eat. That also means they stick around longer. Your body can store extra vitamin D2 and D3 for future use.

And both work to provide similar benefits for your body, like:

• Maintaining and improving bone health
• Strengthening your immune system
• Supporting muscle function
• Improving heart health

Vitamin D2 vs. D3: The differences

Vitamins D2 and D3 come from different sources and work differently in your body. Here’s a quick look for reference, and then we’ll get into more detail:

Sources

If there’s one thing that’s most likely to stand out in your mind about vitamin D, it’s that one way we get our fill is when our bodies create it from sunlight. That’s why it’s often called the “sunshine vitamin.”

What sunlight really does is support the synthesis of vitamin D3 in your body. Vitamin D2 isn’t created by sunlight. Instead, you find vitamin D2 in plant-based foods, like:

• Mushrooms exposed to UV light
• Fortified plant-based milks
• Fortified cereals
• Fortified juices

And in addition to sunlight, you can get your fill of vitamin D3 with foods like:

• Fatty fish, such as salmon, mackerel and sardines
• Animal products like egg yolks and liver
• Fortified dairy products, like cow’s milk and yogurt

Potency

Dr. Goldman shares that vitamin D3 is generally more effective and longer acting than vitamin D2.

“When metabolized, vitamin D3 produces more biologically active compounds your body can use efficiently,” Dr. Goldman explains. “That makes it somewhat more potent than vitamin D2 — though both can effectively help raise vitamin D levels.”

When you get bloodwork and your provider checks your vitamin D levels, the number is a mix of both vitamin D2 and D3. And getting enough of either (or both) of them can help to keep your vitamin D levels in a healthy range.

“Vitamin D deficiency is common, especially among people who get limited exposure to sunlight,” Dr. Goldman reports. “It’s also seen in older adults, people with darker skin tones and people with conditions like osteoporosis or chronic kidney disease.”

Supplementing with vitamin D2 or D3

Both vitamin D2 and vitamin D3 are available as supplements.

Over-the-counter supplements are more likely to be vitamin D3. Vitamin D2 is more often found in prescription-strength supplements from your provider. That’s not a hard-and-fast rule, though. Vitamin D2 is also available over the counter. And sometimes, providers may prescribe vitamin D3.

“In general, vitamin D3 is more commonly recommended as a supplement. It’s more widely available and highly effective,” Dr. Goldman shares.

But there are times when a provider may recommend vitamin D2 instead. Remember that vitamin D2 comes from plant-based foods, so it’s a better choice for people who follow vegan diets.

And while lots of people can benefit from vitamin D supplements, it’s best to talk with a healthcare provider, like a primary care physician, before starting a new supplement.

“Vitamin D is a powerhouse nutrient, but more isn’t always better,” Dr. Goldman warns. “It’s smart to check with your healthcare provider before starting supplements — especially at higher doses — to make sure you’re getting what you need without overdoing it.”