Vitamin D vs D3 (and D2): What Is the Difference?

Vitamin D and D3 are not quite the same: vitamin D3 is cholecalciferol, one form of vitamin D, and "vitamin D" is the family name that also covers vitamin D2 (ergocalciferol). D3 is the kind your skin makes in sunlight; D2 comes from fungi and yeast. Your body activates both in the same two steps, but studies consistently find that D3 raises blood vitamin D levels more than D2. This guide compares vitamin D vs D3, D2 vs D3, and how much you need.

It is educational, not medical advice.

Key Takeaways

• Vitamin D is the family: D3 and D2 are the two forms used in supplements and fortified foods.
• D3 (cholecalciferol) is made in your skin from sunlight and found in animal foods; supplement D3 usually comes from lanolin in sheep's wool, or from lichen for a vegan version.
• D2 (ergocalciferol) comes from fungi and yeast exposed to ultraviolet light, including UV-treated mushrooms.
• D3 raises blood levels more: meta-analyses of head-to-head trials find a larger rise in blood vitamin D with D3 than with D2.
• How much: the adult RDA is 600 IU (15 mcg) a day, or 800 IU (20 mcg) over age 70; the adult upper limit is 4,000 IU (100 mcg).

Vitamin D vs D3 at a Glance

	Vitamin D	Vitamin D3	Vitamin D2
What it is	The family name for the group	One form: cholecalciferol	One form: ergocalciferol
Where it comes from	Sunlight, food and supplements	Made in your skin from sunlight; fatty fish and egg yolk; supplements from lanolin or lichen	Fungi and yeast exposed to UV light
On a label	Check which form is named	Vitamin D3, cholecalciferol or vitamin D (as cholecalciferol)	Vitamin D2, ergocalciferol or vitamin D (as ergocalciferol)
Effect on blood levels	Depends on the form	Raises 25(OH)D more in most trials	Raises it less; about 40% smaller rise with daily D2 in a 2024 review

Is Vitamin D the Same as D3?

When a label or a lab report says "vitamin D," it means the whole group. When it says "vitamin D3," it means one specific form. So all D3 is vitamin D, but not all vitamin D is D3. In practice, many vitamin D supplements contain D3, which is why the two names are often used as if they were the same thing.

The other form you may see is D2. Both are well absorbed in the small intestine, and the body activates both through the same two steps (NIH Office of Dietary Supplements). The difference is where they come from and how strongly they raise your vitamin D levels.

Vitamin D vs D3 on a Supplement Label

On a Supplement Facts panel, the form is usually named next to the vitamin. Vitamin D3, cholecalciferol and vitamin D (as cholecalciferol) all mean D3. Vitamin D2, ergocalciferol and vitamin D (as ergocalciferol) mean D2. If a label says only vitamin D and names no form, check the ingredient list or ask the maker. FDA requires vitamin D amounts on labels in micrograms (mcg), and labels may also show IU in parentheses (NIH ODS). So 25 mcg of vitamin D3 and 1,000 IU of cholecalciferol are the same amount of the same compound.

Vitamin D2 vs D3: Side by Side

	Vitamin D3 (cholecalciferol)	Vitamin D2 (ergocalciferol)
Natural source	Made in your skin from sunlight; found in fatty fish and egg yolk	Fungi and yeast exposed to UV light, such as UV-treated mushrooms
How supplements are made	UV light on a compound from lanolin (sheep's wool), or from lichen	UV light on ergosterol from yeast
Vegan?	Lanolin D3 is not vegan; lichen D3 is	Yes
Effect on blood levels	Raises total vitamin D more in most trials	Raises it less, especially at higher or weekly doses

How Your Body Uses D2 and D3

Whether it comes from sunlight, food or a supplement, vitamin D is not active at first. The body converts it in two steps:

1. In the liver, it becomes 25-hydroxyvitamin D, written 25(OH)D. This is the form measured in a blood test.
2. In the kidneys, it becomes 1,25-dihydroxyvitamin D, the active hormone the body uses.

Both D2 and D3 follow this route (NIH ODS). The question is how much 25(OH)D you end up with from each.

Which Raises Vitamin D Levels More?

Several reviews have pooled the trials that gave people D2 or D3 directly:

• A 2012 meta-analysis found that D3 raised blood 25(OH)D more than D2. The gap was clearest with large single or occasional doses; with daily dosing it was not statistically clear in that analysis (Tripkovic et al., 2012).
• A 2021 review of 24 studies with 1,277 healthy people again found D3 more effective at raising total 25(OH)D, with smaller differences at lower doses (Balachandar et al., 2021).
• A 2024 review limited to daily or weekly dosing found the rise in total 25(OH)D was about 40% smaller with daily D2 than with daily D3 (van den Heuvel et al., 2024).

One winter trial shows what this looks like in real life. Adults took 1,000 IU of D3, 1,000 IU of D2 or a placebo every day for 25 weeks. Those on D3 held their vitamin D level steady through the winter, while total levels in the D2 group ended about 21 nmol/L lower than in the D3 group (Logan et al., 2013). The U.S. National Institutes of Health sums it up the same way: vitamin D3 increases blood 25(OH)D to a greater extent than vitamin D2.

If you avoid animal products, our guide to vegan vitamin D3 explains lichen D3 and how to check a label. Vitamin B12 is another nutrient that comes naturally from animal foods; see vitamin B12 benefits.

D2 or D3: Which Should You Take?

For most people choosing a supplement, D3 is the more efficient option. A few situations change the picture:

• Vegan diets: standard D3 is made from lanolin, so it is not vegan. D2 is, and so is D3 made from lichen.
• Fortified foods: if a fortified food uses D2, it still counts toward your intake.
• Prescribed vitamin D: if a clinician has given you a specific product and dose, follow their plan rather than switching on your own.

For more on choosing and taking D3, see our guide to vitamin D3 supplements and the vitamin D3 ingredient guide.

How Much Vitamin D Do You Need?

Vitamin D is listed in either international units (IU) or micrograms (mcg). One microgram equals 40 IU, so 25 mcg is 1,000 IU. The NIH recommends (NIH ODS):

Group	Recommended daily amount
Adults 19 to 70	600 IU (15 mcg)
Adults over 70	800 IU (20 mcg)
Pregnancy and breastfeeding	600 IU (15 mcg)
Upper limit for adults	4,000 IU (100 mcg)

The upper limit is the most you should take every day without medical supervision. Doses of 1,000 to 2,000 IU a day sit well below it. A blood test is the only way to know your own level.

Food Sources of D2 and D3

Few foods contain much vitamin D. Some examples from the NIH:

• Sockeye salmon, 3 ounces: 14.2 mcg
• Mushrooms exposed to UV light, half a cup: 9.2 mcg (as D2)
• Fortified milk, 1 cup: 2.9 mcg
• One large egg: 1.1 mcg, in the yolk

Sunlight on your skin makes D3, but how much depends on the season, where you live, skin tone, age and sunscreen, so it is hard to count on.

Testing Your Vitamin D Level

A 25(OH)D blood test shows your vitamin D status, whether it comes from D2, D3 or sunlight. The NIH uses these ranges:

• Below 30 nmol/L (12 ng/mL): deficient
• 50 nmol/L (20 ng/mL) or more: adequate for bone health in most people
• Above 125 nmol/L (50 ng/mL): potentially linked to harm

Safety: Can You Take Too Much Vitamin D?

Yes. Too much vitamin D, usually from high-dose supplements rather than sun or food, can raise blood calcium. That can cause nausea, vomiting and muscle weakness, and in serious cases kidney and heart problems (NIH ODS). Stay at or below 4,000 IU a day unless a clinician tells you otherwise, and check with your doctor first if you have a kidney condition, take medicine that affects calcium, or are pregnant.

Vitamin D3 With K2

Vitamin D helps you absorb calcium, and vitamin K2 is involved in how the body uses that calcium. Many people take the two together; our guide to vitamin D3 and K2 explains the research and dosing, and MK-4 vs MK-7 compares the two forms of K2. Magnesium also plays a part in how the body uses vitamin D; see vitamin D and magnesium and boron and vitamin D. If you take magnesium alongside other supplements, see the best time to take magnesium. Our guide to how to choose the best vitamin D3 and K2 supplement lists what to check on the label.

Our Vitamin D3 + K2 Drops pair vegan vitamin D3 from lichen with vitamin K2 as MK-4 and MK-7, one drop a day. For the bigger picture on daily immune support, see our immune system guide.

Frequently Asked Questions

Is vitamin D the same as vitamin D3?

Vitamin D3 is one form of vitamin D. "Vitamin D" is the family name and also covers D2. Many supplements labeled vitamin D contain D3.

What is the difference between vitamin D and D3?

Vitamin D is the general name; D3 (cholecalciferol) is the specific form made in your skin and found in animal foods. The other form, D2 (ergocalciferol), comes from fungi and yeast.

Is D3 better than D2?

For raising blood vitamin D levels, yes. Meta-analyses of head-to-head trials find a larger rise in 25(OH)D with D3, and one 25-week winter trial found D3 kept levels steady while D2 did not.

What does the 3 in vitamin D3 mean?

The numbers simply separate the forms in the vitamin D family. D3 is cholecalciferol and D2 is ergocalciferol; they differ slightly in chemical structure.

Is vitamin D3 vegan?

Not always. Most D3 is made from lanolin in sheep's wool. D3 made from lichen is vegan, as is D2.

How many IU is 25 mcg of vitamin D?

1,000 IU. One microgram of vitamin D equals 40 IU, so multiply micrograms by 40 to get IU.

Is 2,000 IU of vitamin D3 a day safe?

For most healthy adults it is below the 4,000 IU daily upper limit. If you have a medical condition or take other supplements with vitamin D, add up your total and check with your clinician.

Do mushrooms have vitamin D?

Mushrooms exposed to UV light do, as vitamin D2; half a cup can provide about 9 mcg. Mushrooms not exposed to UV light contain much less.

Is cholecalciferol the same as D3?

Yes. Cholecalciferol is the chemical name for vitamin D3, so a label that says cholecalciferol, vitamin D3 or vitamin D (as cholecalciferol) contains the same compound. Ergocalciferol is the chemical name for vitamin D2. The two forms differ only in their side chain, and in head-to-head trials cholecalciferol raises blood 25(OH)D more than ergocalciferol.

Should I take vitamin D or D3?

If a supplement just says vitamin D, check which form it contains, because many contain D3. For most people choosing a supplement, D3 is the more efficient option, since it raises blood vitamin D levels more than D2. D2 and lichen D3 both suit vegan diets. If a clinician has prescribed a specific vitamin D product and dose, follow their plan.

Is calcitriol the same as vitamin D3?

No. Calcitriol, also called 1,25-dihydroxyvitamin D, is the active hormone your kidneys make from vitamin D after the liver step (NIH ODS). It is also a prescription medicine, a vitamin D analog used for specific medical conditions (MedlinePlus). Vitamin D3 is the starting material your body converts.

Does a vitamin D blood test measure D3?

A 25(OH)D blood test is the main indicator of vitamin D status, and it reflects vitamin D from every source: D3 your skin makes in sunlight, plus D2 and D3 from food and supplements (NIH ODS). So the result tells you your total vitamin D status, not only how much D3 you take.

Should you take vitamin D3 with food?

Taking it with a meal that contains some fat is a good habit. The NIH Office of Dietary Supplements notes that fat in the gut enhances vitamin D absorption, although some vitamin D is still absorbed without it. Drops in an oil base and softgels already carry a little fat.

Is vitamin D3 more effective than vitamin D?

Vitamin D3 is vitamin D, so the real comparison is D3 vs D2. In head-to-head trials, D3 raises blood 25(OH)D more than D2. If a label just says vitamin D, check whether it names cholecalciferol (D3) or ergocalciferol (D2).

Does vitamin D2 still count toward my daily vitamin D?

Yes. D2 is well absorbed, the body activates it through the same two steps as D3, and fortified foods that use D2 still count toward your intake. UV-treated mushrooms are one D2 food source; see our list of foods high in vitamin D.

Which form of vitamin D is in Vitamin D3 + K2 Drops?

Vitamin D3. Our Vitamin D3 + K2 Drops use vegan vitamin D3 from lichen with vitamin K2 as MK-4 and MK-7 in an MCT oil base, one drop a day with a meal. Benefits build with consistent daily use: months 1 to 2 can bring early changes, and 3 months and beyond is where the full benefit builds. For how liquid compares with tablets, see vitamin D drops vs pills.

Sources

• NIH Office of Dietary Supplements. Vitamin D: Fact Sheet for Health Professionals. ods.od.nih.gov
• Tripkovic L, et al. Comparison of vitamin D2 and vitamin D3 supplementation in raising serum 25-hydroxyvitamin D status: a systematic review and meta-analysis. Am J Clin Nutr. 2012. PubMed 22552031
• Balachandar R, et al. Relative efficacy of vitamin D2 and vitamin D3 in improving vitamin D status: systematic review and meta-analysis. Nutrients. 2021. PubMed 34684328
• van den Heuvel EG, et al. Comparison of the effect of daily vitamin D2 and vitamin D3 supplementation on serum 25-hydroxyvitamin D concentration and importance of body mass index: a systematic review and meta-analysis. Adv Nutr. 2024. PubMed 37865222
• Logan VF, et al. Long-term vitamin D3 supplementation is more effective than vitamin D2 in maintaining serum 25-hydroxyvitamin D status over the winter months. Br J Nutr. 2013. PubMed 23168298
• MedlinePlus. Calcitriol: Drug Information. U.S. National Library of Medicine. medlineplus.gov

These statements have not been evaluated by the Food and Drug Administration. This content is for education and is not medical advice. Our products are not intended to diagnose, treat, cure or prevent any disease. Talk with a healthcare provider before starting a new supplement if you are pregnant, breastfeeding or taking medication.