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Vitamin D1 vs D2 vs D3: What’s The Difference?

Vitamin D1 vs D2 vs D3: Differences

Despite the name, vitamin D is technically NOT a vitamin but a family of nutrients with similarities in their chemical structures.

These nutrients help your body absorb calcium, build strong bones, and come in multiple forms known as Vitamin D1, D2, and D3.

But what is the difference between vitamin D1 vs D2 vs D3, and what is the best way to maintain healthy vitamin D levels as part of a balanced diet?

Short answer:

Vitamin D is available in two main forms: D2 (ergocalciferol) and D3 (cholecalciferol). There’s no such thing as D1, it’s a common misconception.

However, there’s more to explain and understand which we’ve discussed below.

What is Vitamin D?

Vitamin D is a fat-soluble vitamin that helps your body absorb calcium, regulates bone growth, and supports immune function.

Your body will naturally produce Vitamin D when exposed to sunlight, and you can also get it from dietary sources such as fatty fish, egg yolks, butter, and liver.

However, vitamin D deficiencies are common in developed and developing countries alike (due to time spent indoors and poor diets, respectively), so many people need to take vitamin D supplements.

To help you find the best vitamin D supplements for your needs, this article will explain the difference between D1, D2, and D3 and advise you on how best to maintain healthy vitamin D levels:

What is Vitamin D1?

What is Vitamin D1

In the early 1920s, a German researcher called Adolf Windaus isolated three forms of vitamin D, which he named Vitamin D1, D2, and D3.

However, subsequent researchers discovered that what he called “vitamin D1” was a mixture of compounds rather than a pure vitamin D product, so the term D1 is no longer used.

Subsequently, it’s rather hard to explain the difference between D1 and D2 since “vitamin D1” technically doesn’t exist. However, the other two forms – D2 and D3 – have been extensively researched, so it’s much easier to tell them apart.

Vitamin D2 vs Vitamin D3: Are They Same?

Is Vitamin D2 the Same as Vitamin D3

The two forms of vitamin D important to humans – Vitamins D2 and D3 – have many differences, from their sources to their effects on the human body, as we’ll be explaining shortly.

One of the main differences is that D3 is only found in animals, while D2 comes from plants, with common food sources including:

Sources of Vitamin D2 (ergocalciferol):

  • Mushrooms Grown in UV Light
  • Fortified Foods (such as cereals with added vitamin D)

Sources of Vitamin D3 (cholecalciferol):

  • Oily Fish (such as salmon, mackerel, sardines, etc.)
  • Fish Oil (like cod liver oil, etc.)
  • Liver
  • Egg Yolks
  • Butter

Your Skin Produces Vitamin D3

Another significant difference between vitamin D1 vs D2 vs D3 is that your skin produces Vitamin D3 when exposed to sunlight, which is the primary source of vitamin D for many people.

To be more specific, the ultraviolet B (UVB) radiation in sunlight causes your skin to produce vitamin D3 from naturally occurring 7-dehydrocholesterol compounds in your skin.

In layman’s terms, sunlight equals vitamin D, though many people don’t get their recommended daily allowances this way because they spend too much time indoors or cover up when outside.

If you struggle to get enough sun or are worried about your vitamin D levels during winter, you may need to boost your intake with manufactured supplements.

When Should You Take Vitamin D?

When should you take vitamin D

Vitamin D is an essential vitamin, but many people struggle to get enough through natural sources, leading them to take dietary supplements.

Despite the differences between vitamin D1 vs D2 vs D3, the ways in which you can get the most out of your supplements are much the same.

It is generally best to take vitamin D supplements in the morning as part of your daily routine, as this means you get a consistent, regular dose and give your body plenty of time to absorb the Vitamin D.

What’s more, many people say that taking vitamin D in the evening disrupts their sleep (possibly because it disrupts melatonin production), although there is little scientific evidence of this.

What is the best way to absorb vitamin D?

Because vitamin D is a fat-based vitamin, taking your supplements with fat (in the form of cod liver or with a fatty meal, for example) is the best way to improve absorption.

All forms of vitamin D are fat-based, so forget about the difference between D1 and D2, and make sure to take your vitamin D supplements with a meal for the best results.

According to a study of 17 people, taking vitamin D with the largest meal of the day improved vitamin D blood levels by 50% over 2-3 months, much better than taking it on its own.

However, you don’t need to break your diet to have a fatty meal, as nuts, eggs, oily fish, and full-fat dairy products are all nutritious sources of fat that help boost your vitamin D absorption.

What Are the Signs of Low Vitamin D?

signs of low vitamin D

Vitamin D is an essential vitamin with some powerful benefits, but it can be hard to get enough from natural sources, especially if you spend a lot of time indoors.

Even without considering the difference between vitamin D1 vs D2 vs D3, vitamin D deficiency is the most common form of malnutrition globally, though it is easily cured with supplements.

If you aren’t getting enough vitamin D in your diet or spending enough time in the sun, you could be suffering from a vitamin D deficiency without realizing it. For most people, the symptoms of vitamin D deficiencies are mild, but they can include:

  • Getting sick a lot: Vitamin D helps support your immune system, so a deficiency may cause you to get sick more often, especially over winter.
  • Feeling tired: Many studies have linked fatigue to low vitamin D levels (across all forms of vitamin D)
  • Bone pain: Vitamin D helps you absorb calcium, so a shortage of vitamin D may cause a deficiency of calcium, compromising your bone health.
  • Depression: Numerous studies have linked vitamin D deficiencies to depression, likely due to the reduced sunlight and an increase in cases of Seasonal Affective Disorder (SAD) in winter.
  • Reduced Healing: Studies suggest that vitamin D helps control inflammation, fight infection, and boost healing, so slow healing may signify a vitamin D deficiency.

Vitamin D1 vs D2 vs D3: Which Is Best?

Vitamin D1 vs D2 vs D3

Now that we’ve highlighted the potential dangers of vitamin D deficiencies, you must be wondering about which form of vitamin D is best.

While your body can effectively absorb the two main forms of Vitamin D (D2 and D3) into the bloodstream, your liver metabolizes them differently, making one more effective than the other.

Your liver metabolizes both Vitamin D2 and D3 into calcifediol – the main circulating form of vitamin D – though vitamin D3 is more effective at raising your calcifediol than D2.

One study found that vitamin D3 was nearly twice as effective as D2 for increasing calcifediol levels, so make sure that your supplements use vitamin D3 for the best results.

Frequently Asked Questions

How to explain what D1 is?

Although it doesn’t technically exist, vitamin D1 can be explained as a mixture of lumisterol and calciferol, obtained by ultraviolet irradiation of ergosterol. The term “Vitamin D1” was used in the past to refer to a compound that was a mixture of compounds, but it’s not used today.

What’s the difference between D2 and D3?

The main difference between Vitamin D2 vs D3 is their source.. Vitamin D2 comes from plant sources and is often added to foods whereas vitamin D3 is made by your skin in sunlight and can also be found in animal-based foods.

What’s vitamin D1’s other name?

There are no other names for vitamin D1 since it’s a no longer used term.


While the difference between vitamin D1 vs D2 vs D3 is technically a trick question, there are some simple rules you should remember. Try to get plenty of sunshine, fatty fish, and nuts, or make sure to take your vitamin D3 supplements with food, preferably in the morning.

Fortunately, the symptoms of most vitamin D deficiencies tend to be mild, and you can easily find supplements online to maintain healthy levels if you struggle to get enough through natural sources.

If you think you might have a vitamin D deficiency, you should consult your doctor in the first instance or read our blog on how to restore Vitamin D levels to learn more.

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Written and Researched by

SupplementsYouCanTrust is made up of passionate health writers dedicated to providing reliable information on supplements and vitamins. With backgrounds in nutrition, medicine, and research, our team brings a diverse range of perspectives and expertise to the table.
Dr Wasim Khan

Medically Reviewed by

Dr. Wasim Khan’s areas of expertise lie in understanding the role of dietary supplements and vitamins in healthcare. His in-depth knowledge allows him to provide comprehensive advice and help you make informed decisions about your nutritional intake and supplement usage.

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