Vitamin D vs. D3: Is There a Real Difference?

Many people know vitamin D as the ‘sunshine vitamin’ because our bodies produce it when exposed to sunlight. But what about vitamin D3? Are they the same, or is there a real difference?

Although often used interchangeably, vitamin D actually refers to a group of nutrients, primarily vitamin D2 and vitamin D3, rather than a single compound. Both forms support strong bones, immune function, and calcium-phosphate balance.

I’ve personally noticed that spending time in the sun lifts my mood and energy, likely due to vitamin D production. However, since many people have limited sun exposure, they often turn to vitamin D supplementation. With so many options available, though, it’s easy to feel confused.

In this article, we’ll break down the difference between vitamin D and D3, why they’re so important, the different ways we can get them, and the potential risks of deficiency. Understanding their role in your health can help you make informed choices.

What is vitamin D?

Vitamin D is a fat-soluble vitamin. You can get it naturally from some foods, find it added to others, or take it as a supplement. Your body also makes it on its own when sunlight hits your skin.

Vitamin D helps the body absorb calcium and phosphate from ingested food, keeping bones strong and healthy. Without enough vitamin D, bones can become weak, thin, or deformed. A vitamin D deficiency may lead to serious conditions such as rickets in children and osteoporosis in older adults.

Vitamin D does more than just maintain bone health. It reduces inflammation, supports the immune system, aids muscle performance, and even helps regulate blood sugar. However, before vitamin D can be utilized by the body, it must first be activated in the liver and kidneys. This activation process is essential for its widespread benefits, as many body parts rely on it for overall health.

Vitamin D comes in two main forms:

• Vitamin D2 (ergocalciferol)
• Vitamin D3 (cholecalciferol)

Although both form blood levels of vitamin D, they come from different sources and have slightly distinct molecular structures.

Vitamin D2 vs D3: how do they differ?

The key differences between vitamin D3 and D2 are their source and effectiveness. Vitamin D3, found in animal-based foods and naturally produced by the body when exposed to sunlight, is more potent and better absorbed. Vitamin D2, primarily sourced from plants like UV-exposed mushrooms and supplemented foods, is less effective and has a shorter duration of action.

Both D2 (ergocalciferol) and D3 (cholecalciferol) can raise vitamin D in the blood. They are processed in the liver into 25(OH)D, the main circulating form, and then activated in the kidneys into the active hormone 1,25(OH)₂D. While both regulate levels of calcium, phosphate, and support other essential physiological processes, they travel through the bloodstream by binding to proteins like DBP (vitamin D-binding protein) and albumin, ensuring the body can use them as needed.

Studies show that, when taken in daily doses, vitamin D2 raises vitamin D levels 40% less than vitamin D3. Additionally, body weight should be considered when evaluating how well vitamin D2 and D3 supplements work. Vitamin D is fat-soluble and tends to be stored in fat tissue. Individuals with higher body fat may require higher doses of vitamin D to achieve adequate blood levels.

To better understand the key differences between vitamin D2 and D3, the following table summarizes their characteristics.

Choosing vitamin D supplements: which one is better for you?

A meta-analysis published in the American Journal of Clinical Nutrition shows that vitamin D3 is more effective than vitamin D2 at raising serum vitamin D concentrations. When selecting a supplement, choosing one that specifically lists vitamin D3 as the active form is best.

However, when deciding between vitamin D3 and D2 supplements, consider the following factors:

• Effectiveness. Vitamin D3 is generally more effective at raising and maintaining vitamin D in the blood and has a longer half-life, meaning it stays active in the body longer. Vitamin D2 is still effective but may not be as potent for long-term maintenance of vitamin D.
• Dietary preferences and restrictions. For those following a vegan or vegetarian diet, vitamin D2 is plant-based but found in very few foods. Vitamin D3 is typically animal-derived (from food sources like beef liver or fatty fish liver oils), though vegan-friendly D3 from lichen is available.
• Health conditions. Some health conditions, such as kidney disease, may affect how the body processes vitamin D. It's important to consult a healthcare provider to determine the best form based on individual human health needs.
• Sun exposure. If sunlight is limited, vitamin D3 may be more effective in raising serum vitamin D levels, especially for individuals with vitamin D deficiency.

Personal needs vary, so it's important to consult a healthcare provider to determine the right dosage of your vitamin D supplement. Factors like diet, sun exposure, and overall health can influence how much fat-soluble vitamin D you need.

Vitamin D deficiency: how much vitamin D is enough?

According to the National Institutes of Health, adults aged 19 to 70 should aim for a daily intake of 600 IU (15 mcg) of vitamin D, while adults over 70 should aim for 800 IU (20 mcg) per day. Maintaining adequate vitamin D levels is important, as insufficient vitamin D can lead to health issues.

Vitamin D deficiency is a global public health issue. About 1 billion people worldwide have vitamin D deficiency, while 50% of the population has vitamin D insufficiency.

Vitamin D can be low for several reasons:

1. Poor diet or absorption. ​Conditions such as celiac disease, Crohn's disease, and gastric bypass surgery can impair the body's ability to absorb vitamin D due to their effects on the gastrointestinal system. For instance, celiac disease can cause fat malabsorption, leading to reduced vitamin D absorption. Similarly, gastric bypass surgery alters digestive processes, potentially reducing the body's ability to absorb vitamins. Older adults also tend to get less vitamin D from food. The digestive system's ability to process and absorb nutrients, including vitamin D, tends to decline with age.
2. Insufficient sunlight. To prevent deficiency, it's recommended to get around 5 minutes of sun daily, ensuring a good amount of skin is exposed. As people age, their ability to produce this essential hormone from sunlight diminishes. Individuals with darker skin tones also generate less of it, and those who spend a lot of time indoors or frequently use sunscreen may not produce enough.
3. Chronic conditions. Some chronic liver diseases and kidney conditions can prevent the body from converting the vitamin into its active form.
4. Medications. Certain drugs, like phenobarbital and rifampin, can speed up the breakdown of vitamin D in the liver.
5. Resistance to vitamin D. In rare cases, people may develop a condition called hereditary vitamin D-resistant rickets, where the body’s tissues don’t respond properly to vitamin D.

Most people with low vitamin D don’t show any symptoms. However, even mild long-term deficiency can cause low calcium levels and higher parathyroid hormone, increasing the risk factors of osteoporosis, falls, and fractures, especially in older adults. If vitamin D deficiency is severe and prolonged, it can cause symptoms like bone, joint, and muscle pain, tiredness, muscle twitches, and weakness. In children, signs of insufficient vitamin D may include irritability, tiredness, developmental delays, bone changes, or fractures. If you get a limited amount of vitamin D from sun exposure and foods naturally, consider dietary supplements to fill in any nutritional gaps of vitamin D and D3.

“Vitamin D testing should be done cautiously, as it is not recommended for routine screening in the general population, as emphasized by many health authorities such as the U.S. Preventive Services Task Force and the Endocrine Society,” says Linas Černiauskas, PhD candidate in Medicine at Vilnius University.

Linas Černiauskas, PhD Candidate

Health Content Researcher

Testing is most appropriate for individuals at risk for vitamin D deficiency, including older adults, those with limited sun exposure, chronic illnesses affecting nutrient absorption or metabolism, darker skin tones, and certain medications. In these cases, measuring blood 25-hydroxyvitamin D (25(OH)D) levels helps guide supplementation decisions made by doctors. The goal is to identify vitamin D deficiency in at-risk individuals who may benefit from supplementation and to avoid unnecessary supplementation in those who are not deficient, preventing the risks associated with long-term vitamin D oversupplementation.

“From a laboratory medicine perspective,” Černiauskas adds, “it is recommended to discontinue vitamin D supplements for at least two weeks before testing. This allows for accurate assessment of vitamin D levels, ensuring that test results reflect the individual’s true status and help to evaluate whether the vitamin D supplementation was effective in increasing the baseline vitamin D levels.”

Which foods can boost your vitamin D2 and D3?

To boost your vitamin D levels, focus on foods that contain either vitamin D2 or D3.

Foods rich in vitamin D2 (ergocalciferol):

• Mushrooms
• Plant-based milk (soy, almond, oat)
• Fortified orange juice
• Fortified cereals
• Fortified tofu

Foods rich in vitamin D3 (cholecalciferol):

• Fatty fish (salmon, mackerel, sardines, tuna, herring)
• Cod liver oil
• Egg yolks
• Liver (beef, chicken)
• Fortified cheese
• Fortified milk
• Fortified yogurt

The final verdict on vitamin D and D3

I hope this article has helped you understand the nuances between vitamin D2 and D3 and has empowered you to take control of your health. Both vitamin D forms contribute to bone strength and immune system response, yet vitamin D3 stands out for its superior ability to boost and sustain serum vitamin D levels within a proposed healthy range.

My experience has taught me the importance of sufficient sun exposure or vitamin D supplementation, especially during darker months. If you’re weighing your options, remember that your unique lifestyle, diet, and health conditions matter. A quick consultation with health professionals can help tailor the right approach, suggest dietary supplements, and recommend a blood test to measure vitamin D in your blood to ensure you have healthy vitamin D levels.