Vitamin D2 vs D3: What Should You Know?

The Basics of Vitamin D

Before exploring the specifics of vitamin D2 vs D3, what is vitamin D?

Vitamin D is a fat-soluble vitamin that helps regulate your immune system function and bone growth, and it also helps your body absorb calcium.

When you’re exposed to sunlight, your body can produce vitamin D, but if you live somewhere there’s not a lot of sunlight, it’s winter, or you don’t go outdoors that much, you may need to get vitamin D from your diet or a supplement. Foods with vitamin D include egg yolk,  liver, butter, and fish oils. Some foods are also fortified with vitamin D, meaning they’re added. This is true of breakfast cereals and milk, for example.

If you’re taking vitamin D as a supplement, keep in mind that it’s fat-soluble. As such, try to either take your supplement with a meal containing fat or choose an oil-based supplement. We tend to prefer oil-based liquid vitamin D supplements because they’re easier for your body to absorb.[1]

Vitamin D supplements are available in two forms: vitamin D2 and vitamin D3. Vitamin D2 is also called ergocalciferol, and D3 is also called cholecalciferol.

An Overview of Vitamin D2 vs D3

The following are some of the primary things to know about the differences and similarities seen when comparing vitamin D2 vs vitamin D3. 

What is Vitamin D2?

Vitamin D2 or ergocalciferol, helps your body absorb calcium and phosphorus. Sources of vitamin D2 include mushrooms but only if they’re grown in UV light, and fortified foods. Vitamin D2 is cheaper to make, so it’s often what’s included in vitamin D fortified foods. Vitamin D2 comes primarily from plant sources and fortified foods.

If you were to choose a vitamin D2 supplement, there’s concern that it could be lower quality than a D3 supplement. For example, when comparing vitamin D2 vs D3, vitamin D2 is more susceptible to fluctuations in temperature, so your supplement could degrade faster. You would need to make sure you were storing a D2 supplement in a cool, dry place and out of the way of direct sunlight.

What is Vitamin D3?

If we’re comparing vitamin D3 vs D2, vitamin D3 is the preferred version to supplement with.

When your skin is exposed to sunlight, it makes D3. If you get regular sun exposure, you may not need a D supplement at all.

If you do have a vitamin D deficiency and you need to supplement, choose vitamin D3.

The primary difference when comparing vitamin D2 vs vitamin D3 is their ability to raise your blood levels of vitamin D. Both can be absorbed in your bloodstream, but they’re metabolized differently by the liver.

Your liver will metabolize D2 into something called 25-hydroxyvitamin D2. Your liver metabolizes vitamin D3 into 25-hydroxyvitamin D3.

When vitamin D is circulating in your body, it’s in the form of calcifediol. Your blood levels of calcifediol are how your vitamin D levels are determined. If you take a D2 supplement, you’re likely going to get less calcifediol in your blood than you would with D3.

Studies show vitamin D3 is the way to go to truly raise your blood levels of vitamin D.[2],[3]

What to Know About Choosing a Vitamin D Supplement

If you need a vitamin D supplement and it’s something your doctor recommends, you should aim to take anywhere from 400 to 800 IU of vitamin D3 a day. Take your supplement with a food that’s considered healthy fat, such as avocado, because this will help you absorb it better. Don’t take more than 4,000 IU of vitamin D a day, because it can lead to toxicity.

If you’re 70 or older, you should aim for around 800 IU of vitamin D a day, because as you get older, it becomes more difficult for your body to produce and use vitamin D.

It’s also important to understand that vitamin D deficiency is on the rise. This is for many different reasons. One is the fact that we now protect ourselves from the sun more than ever before with sunscreen and coverage, which can reduce our vitamin D production by 95%. Of course, it’s important to protect yourself from exposure, but at the same time, realize the effects that may have on your vitamin D levels.

If you’re overweight or older, you may also be at greater risk of vitamin D deficiency, as are people with darker skin.

Final Thoughts—Vitamin D2 vs D3

Vitamin D intake is important for all of us, particularly as we head into winter. Speak to your doctor about whether or not you should take a supplement.

As you choose a vitamin D supplement, you’ll likely see that you have an option between vitamin D2 and D3.

When comparing vitamin D2 vs D3, keep in mind that D3 is better at raising vitamin D levels in your blood. A vitamin D3 supplement will likely be more potent, fast-acting and generally effective than a D3 supplement. Vitamin D3 is also higher-quality and is what your skin makes in response to sun exposure.

If you have questions about your vitamin D status, speak to your doctor who can test your levels and help you determine if you need a supplement.

We encourage you to check out our full posts on vitamin D deficiency and vitamin D supplements.

[1] https://pubmed.ncbi.nlm.nih.gov/20425758/

[2] https://pubmed.ncbi.nlm.nih.gov/22552031/

[3] https://pubmed.ncbi.nlm.nih.gov/23792937/