Vitamin D vs. D3: What’s the Difference?

Vitamin D is a fat-soluble vitamin that supports many body processes and vital organs. It is found in certain foods and dietary supplements. The body also produces vitamin D after exposure to sunlight, which is why you may hear people refer to it as the “sunshine vitamin.”

Two types of vitamin D are essential for human health: vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). Though both types are referred to as “vitamin D,” there are some key differences between the two.

This article explores the differences between vitamin D and D3, their sources, and their roles in the body. It also discusses ways to get enough vitamin D to support your health. 

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What Is Vitamin D?

Vitamin D is a micronutrient that is important for human health. One of the primary roles of vitamin D is calcium and phosphorus absorption, which are essential for bone mineralization and density. Along with calcium, vitamin D helps keep your bones strong and prevents osteoporosis. Vitamin D also has a role in the following:

"Vitamin D" is an umbrella term for two different forms of the vitamin: vitamins D2 and D3. Though the two forms offer the same health benefits, they are obtained from different sources and have slightly different molecular structures.

Vitamin D2

Vitamin D2, or ergocalciferol, is found in fungi (mushrooms) and yeasts. Vitamin D2 is produced by exposing a yeast called ergosterol to ultraviolet (UV) radiation. Foods fortified with vitamin D, such as plant-based milk, cereal, and orange juice, contain vitamin D2.  Vitamin D2 is also available as a dietary supplement in capsules, sublingual (beneath the tongue) tablets, and liquid forms.

Once consumed, vitamin D2 is absorbed in the small intestine and transported to the liver, which converts it to 25-hydroxyvitamin D2. From there, it is converted to the active form of vitamin D (calcitriol) in the kidneys. This process enables your body to use the vitamin and reap its health benefits. 

Vitamin D3

Vitamin D3, or cholecalciferol, is produced by the body when the skin is exposed to sunlight. It is also found in several animal-based food sources, such as fatty fish (e.g., salmon, mackerel), egg yolks, and beef liver. Cow’s milk and other dairy products are often fortified with vitamin D3. Vitamin D3 is available as a dietary supplement in liquid drops, capsules, and sublingual tablet forms.

After you spend time in the sun, your body converts sunlight into vitamin D3, which is then transported to the liver and converted to 25-hydroxyvitamin D3. In the kidneys, it is converted into calcitriol—the active form of vitamin D your body uses to support overall health. 

Vitamin D2 vs. D3

Though vitamins D2 and D3 have different molecular structures, they are metabolized into the same active form of vitamin D the body needs to support your health: calcitriol.


Once vitamins D2 and D3 are converted into the bioactive form of vitamin D, it plays a vital role in many body processes. Vitamin D promotes the absorption of calcium and phosphorus to support bone health and muscle strength. It also boosts immune function, reduces inflammation, supports cardiovascular health, and may protect against cancer.

People who do not consume enough vitamin D–rich foods or do not spend enough time in the sun may have a vitamin D deficiency. Certain populations are more likely to be deficient in vitamin D, including those who:

  • Get limited sun exposure (e.g., living in cold climates, individuals who are housebound) 
  • Have dark skin tones because dark skin absorbs less sunlight 
  • Have certain medical conditions that affect the absorption of vitamin D (e.g., liver disease, cystic fibrosis, celiac disease)
  • Take medications that affect vitamin D metabolism (e.g., glucocorticoids, anti-seizure drugs

Signs of a Vitamin D Deficiency

A vitamin D deficiency does not always cause symptoms. However, when it does, symptoms can include:

  • Fatigue
  • Muscle pain and weakness 
  • Bone pain 
  • Mood changes (e.g., depression) 
  • Rickets (in children), which is when bones weaken and cause bowed or bent bones (e.g., bowed legs)

Vitamin D deficiency is linked to an increased risk of fractures, diabetes, cardiovascular disease, and depression. Researchers are exploring the potential connection between vitamin D deficiency and inflammatory and autoimmune health conditions, such as multiple sclerosis and rheumatoid arthritis.


If you have a vitamin D deficiency, you may wonder whether vitamins D2 or D3 supplements would be better for boosting your vitamin D levels. While vitamin D2 and D3 both increase vitamin D in the body, research shows that vitamin D3 is more effective. Vitamin D3 is more easily absorbed by the body and helps sustain healthy vitamin D levels for extended periods.

Though they are more similar than different, vitamins D2 and D3 may affect gene expression differently, particularly with genes associated with immune function. Research suggests that vitamin D3 is more effective at regulating gene expression, helping stimulate the immune system to fight off bacteria and viruses to keep you healthy.


The recommended dosage for vitamins D2 and D3 supplements varies based on age, weight, and overall health. Before supplementing with any form of vitamin D, talk to your healthcare provider, who can determine the appropriate dose to meet your needs. 

The recommended daily allowance (RDA) for vitamin D is listed in international units (IU) and micrograms (mcg) based on your age:

  • Infants 0–12 months: 400 IU (10 mcg) 
  • Children ages 1–18: 600 IU (15 mcg) 
  • Adults ages 19–70: 600 IU (15 mcg) 
  • Adults 71 or older: 800 IU (20 mcg) 

If a healthcare provider has diagnosed you with vitamin D deficiency, they may recommend higher doses until your body's vitamin D levels are restored. 

Drug Interactions and Warnings

Both forms of vitamin D are considered safe and well-tolerated when taken in recommended doses. Vitamin D is fat-soluble, which means it is stored in the body. Taking too much can build up in the body and lead to vitamin D toxicity, which can harm your health. Vitamin D toxicity symptoms include:

  • Nausea
  • Vomiting 
  • Reduced appetite 
  • Constipation 
  • Weakness 
  • Unintentional weight loss 

Excess vitamin D levels in the body also increase calcium levels in your blood (hypercalcemia), which can cause irregular heart rate, excessive thirst, dehydration, confusion, delirium, and coma in severe cases. Contact a healthcare provider if you experience these symptoms while taking a vitamin D supplement.


Vitamin D supplements may interact with certain prescription medications or supplements and change how these medicines work in your body or cause harmful side effects. Talk to a healthcare provider before starting a vitamin D regimen if you take any of the following medications or supplements:


Vitamin D supplementation is not recommended for everyone, and certain people should exercise caution or avoid vitamin D supplements. Do not take vitamin D supplements if you:

  • Are allergic to aspirin or ergocalciferol (vitamin D2)
  • Have malabsorption syndrome (disorder in which the small intestine cannot absorb enough nutrients from food)
  • Have hypercalcemia (high calcium levels in the blood) 

What’s the Best Way to Get Vitamin D?

Sunlight exposure and dietary sources are the best ways to get vitamin D, as follows: 

  • Sunlight exposure: Your body converts sunlight into vitamin D when your skin is exposed to the sun. Spending just 10–15 minutes in the sun without sunscreen a few times a week can help your body produce adequate amounts of vitamin D.
  • Dietary sources: Vitamin D can be found in fatty fish, egg yolks, organ meats, and fortified foods like milk, cereal, and orange juice. Getting sufficient amounts of vitamin D through diet alone can be challenging, especially for people who follow a vegetarian or vegan diet. 
  • Supplements: Vitamin D supplements can help ensure you get adequate amounts of vitamin D to support your health, especially if you have limited sun exposure or have difficulty absorbing vitamin D from food sources. 

Which Is Better: D2 or D3?

Vitamin D3 is converted into the active form of vitamin D (calcitriol) when consumed or after spending time in the sun. Both vitamins D2 and D3 effectively raise blood levels of vitamin D. Still, research shows that vitamin D3 is more easily absorbed and is better at maintaining healthy levels of vitamin D than D2.

Vitamin D3 is the form that is naturally produced in the body after sunlight exposure, which may explain why the body seems to absorb and use it more effectively than vitamin D2.

Ultimately, the best vitamin D supplement depends on your health and needs. Speak with a healthcare provider to determine which form and dose of vitamin D is best for you. 


Vitamin D is an essential micronutrient crucial in maintaining bone health, immune function, and overall health. There are two primary forms of vitamin D: vitamin D2 and vitamin D3. Vitamin D3 is the form of vitamin D produced in the body after sunlight exposure. It appears to be more effective than vitamin D2 at raising and maintaining blood levels of vitamin D. 

Vitamin D can be obtained through sunlight exposure, dietary sources, and supplements. The recommended daily vitamin D intake varies depending on age and overall health. Speak with a healthcare provider to determine which form of vitamin D is best for your needs. 

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Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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