Vitamin D vs. D3: what's the difference?

Updated on June 30, 2026 by Neka Miller, PhD. To give you technically accurate, evidence-based information, content published on the Everlywell blog is reviewed by credentialed professionals with expertise in medical and bioscience fields.

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Table of contents

• What Is Vitamin D?
• What's the Difference Between Vitamin D and Vitamin D3?
• Similarities Between Vitamin D2 and Vitamin D3
• Which Form of Vitamin D Is Better?
• Signs You May Be Vitamin D Deficient
• How to Check Your Vitamin D Levels

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If you've been learning more about vitamin D or have been paying attention to the labeling on supplement bottles, you might have noticed that the term "vitamin D3" comes up. This might spring the following question to mind: vitamin D vs. D3—is there a difference and what even is D3?

Find the answer to that question in the article below, so read on for more.

What Is Vitamin D?

Vitamin D is a fat-soluble vitamin that is found in certain foods and supplements, but it can also be made by the body when your skin is exposed to the ultraviolet rays of sunlight.[1] It is actually the only vitamin of the 13 essential vitamins that your body can manufacture on its own. However, many people become deficient in vitamin D because they don't get enough sunlight, and nearly 50% of people globally experience vitamin D insufficiency.[1,2]

One of the main roles of vitamin D is promoting calcium absorption, which allows for proper bone mineralization and growth. It also plays diverse roles throughout the body, including reducing inflammation, supporting immune function, and metabolizing glucose.[1]

What's the Difference Between Vitamin D and Vitamin D3?

There are two possible forms of vitamin D in the human body: vitamin D2 and vitamin D3. Both D2 and D3 are simply called "vitamin D," so there's no meaningful difference between vitamin D3 and just vitamin D.

That being said, it can be worth understanding how vitamin D2 and D3 specifically are different from each other—so here's a quick rundown [2]:

• Vitamin D3 is the form of vitamin D the human body makes when sunlight strikes the skin. The body can't manufacture vitamin D2.
• Vitamin D3 is found in animal sources of foods, like fatty fish and fish oil, liver, organ meats, and egg yolks.
• Vitamin D2 primarily comes from plant sources (like wild mushrooms), and forms when certain kinds of plants are exposed to ultraviolet light from the sun.

Similarities Between Vitamin D2 and Vitamin D3

While their chemical makeup and sources differ, vitamin D2 and vitamin D3 have much more in common. When ingested, both vitamin D2 and D3 have to pass through the liver and kidneys, where they get processed into the active, usable form of vitamin D.[2] Both forms of vitamin D are readily available as over-the-counter oral supplements. However, high doses of vitamin D2 (up to 50,000 IUs, or International Units) are only available through a prescription.

Which Form of Vitamin D Is Better?

Research suggests that vitamin D3 is more effective than D2 at raising and maintaining vitamin D levels in the blood. Studies show that D3 produces more biologically active compounds when metabolized and remains in the bloodstream longer, making it the preferred supplemental form for most people.[2]

That said, vitamin D2 comes from plant-based sources, making it a practical choice for those following a vegan diet. Vegan D3 derived from lichen or algae is also increasingly available for those who want the benefits of D3 without animal-derived ingredients.

Regardless of which form you take, getting the right dose matters. Most experts recommend 600 to 800 IUs of vitamin D per day for most adults.[1] If you are deficient, your healthcare provider may recommend higher supplemental doses. An at-home vitamin D test can help you understand where your levels stand before starting supplementation.

Signs You May Be Vitamin D Deficient

Nearly half of people globally experience vitamin D insufficiency.[1] Common signs of vitamin D deficiency may include:

• Fatigue and low energy
• Bone pain or muscle weakness
• Frequent illness or infections
• Mood changes, including feelings of depression

If any of these apply to you, it's worth checking your levels before deciding whether to start supplementation and which form to choose.

How to Check Your Vitamin D Levels

If you want to see what your vitamin D levels are like, the Everlywell Vitamin D Test is an easy at-home option that lets you conveniently collect a sample at home and send it to a lab for accurate testing (a prepaid shipping label is included with the kit).

References

1. Vitamin D. NIH, Office of Dietary Supplements. https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/. Accessed June 30, 2026.
2. Nair R, Maseeh A. Vitamin D: the "sunshine" vitamin. J Pharmacol Pharmacother. 2012;3(2):118-126.