Vitamin D2 vs D3: Which Is Better for Bone Health and Immune Support?

Ever stood puzzled in the supplement aisle, wondering why there's a D2 and a D3—and what in the world sets them apart?

You're not alone—an estimated one-third to one-half of adults worldwide have suboptimal vitamin D levels, an essential nutrient linked to everything from bone strength and calcium absorption. It also affects your body's natural immune defense and much more!

Vitamin D2 vs D3: What’s the real difference?

When browsing the supplement aisle, you may notice two types of vitamin D: D2 and D3. You might wonder, what’s the difference, and which one is better for your health?

Let’s start with their basic definitions. Vitamin D is an essential nutrient that supports bone health, muscle function, and immune system performance.

Both D2 (ergocalciferol) and D3 (cholecalciferol) are forms of vitamin D, but they come from different sources and have slight differences in how they’re processed by your body.

Vitamin D2 is mainly found in plant foods and fortified foods, whereas D3 comes from animal-based foods and is also made by the skin when exposed to sunlight.

Sources of vitamin D2 and D3

Here’s how you can get each type of vitamin D in your diet:

Now that we’ve covered food sources, you might also be wondering: how much vitamin D can you really get from food vs. sunlight?

Most people only get small amounts from food; sunlight is the most important natural source for D3, but this can vary greatly by season and skin exposure.

How does your body use D2 vs D3?

Let’s see what happens after you eat a supplement for each form.

Both D2 and D3 are absorbed in the small intestine and changed in the liver and kidneys to the active form of vitamin D that your body can use. Both forms help your body absorb calcium, which is important for strong bones.

Still wondering about “the active form”? Your body turns both D2 and D3 into 25-hydroxyvitamin D (25(OH)D), the marker doctors check to determine your vitamin D status, and then into calcitriol, the active hormone.

However, recent research suggests that D3 is more effective than D2 at raising and keeping overall vitamin D levels in your blood.

A meta-analysis of randomized controlled trials showed that vitamin D3 supplementation raises blood 25-hydroxyvitamin D levels more effectively compared to vitamin D2—and this matters because higher, stable vitamin D levels are linked to better bone strength and immune health. D3 may be more reliable for ongoing needs.

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Comparison table: D2 vs D3

Before exploring practical supplementation, let’s compare their key features.

Why is D2 sometimes used for prescriptions if D3 is more effective? D2 is historically used in pharmaceutical high-dose treatments and is vegan-friendly, which makes it better in specific cases.

Daily vitamin D requirements

Now, let’s cover how much vitamin D you actually need. Here’s a quick reference to the Recommended Dietary Allowance (RDA) (covers food + supplements):

But wait—does recommended intake change depending on whether you use D2 or D3? No matter the type, the RDA covers total vitamin D intake from both dietary and supplemental sources.

While you can get some vitamin D from foods, few foods contain high levels naturally. This is why:

• People with darker skin absorb less D3 from sunlight.
• If you live far from the equator, your seasonal sunlight is limited.
• Wearing sunscreen regularly can lower your skin's vitamin D3 production.

Vitamin D deficiency: Signs and solutions

Let’s check what happens if you’re running low—and what you can do next.

Vitamin D deficiency can lead to weakened bones, muscle weakness, and in severe cases, rickets in children or osteomalacia in adults.

If you think you might be low on vitamin D, talk to your doctor, who may recommend a supplement. D3 is usually preferred for supplementation because it stays in your body longer and raises blood levels more efficiently. D3 sticks around longer in your system, so your vitamin D levels won’t fall as quickly between doses.

Food sources of vitamin D2 and D3

Let’s break down actual food sources side by side.

Still curious about added nutrients? Most U.S. Cow’s milk is supplemented with D3, while plant-based milks and cereals often use D2, making label reading important if you avoid animal products.

Should you supplement with D2 or D3?

Now for the big question on supplements.

We can meet our vitamin D needs with either form, but vitamin D3 is generally preferred because it’s more effective at keeping those levels over time. Vitamin D2 supplements still remain effective, especially in treating deficiency, and may be prescribed at high doses.

Wondering which is best for vegans? D2 is plant-based and vegan, while most D3 is animal-derived; however, vegan-friendly D3 supplements made from lichen are now available. Sunlight can be surprisingly potent.

Frequently asked questions (FAQ)

Here are some of the most frequently asked questions about vitamin D2 and D3.

Final thoughts

Vitamin D2 and D3 might seem similar at a glance, yet they're very different when it comes to their origin, use, and how long they last in your system. Vitamin D3 clearly comes out ahead, offering better efficiency in raising and keeping vitamin D blood levels, especially for ongoing supplementation.

But remember: choosing between D2 and D3 can also depend on your dietary choices or specific health needs. If you're vegan, D2—or even vegan-friendly D3 sourced from lichen—could be your best bet.

Think for a moment: Are you meeting your daily vitamin D needs effectively, or is it time for a focused adjustment in your supplementation plan? Better yet, discuss your vitamin D status with your healthcare provider to see the best solution for your unique health situation.

Sources and references

• Comparison of vitamin D2 and vitamin D3 supplementation in raising serum 25-hydroxyvitamin D status: a systematic review and meta-analysis - PubMed
• Vitamin D - Health Professional Fact Sheet