Vitamin D2 (Ergocalciferol) vs. Vitamin D3 (Cholecalciferol): Which One Is Better?

Vitamin D is an important nutrient for your bones, muscles, and immune system. And a vitamin D deficiency can lead to serious health problems, like depression, osteoporosis, and hair loss. So it’s no surprise that many people take vitamin D supplements. But there are actually two different versions available: vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). So we’ll clear up the confusion around which one is better. 

What is vitamin D and how do I get it?

Vitamin D is an important ingredient in many different cellular processes in the body. It’s well known for keeping your bones strong. But it also plays a role in other body functions, for example:

• Muscle strength

• Immunity

• Calcium and glucose metabolism

There are two natural sources of vitamin D:

• Food: There are only a small number of foods that naturally contain vitamin D. Some of the best sources include liver, oily fish, mushrooms, and egg yolks. It’s more common to find foods that are artificially fortified with vitamin D, like cereals and milk.

• Sunlight: Your body can actually make its own vitamin D. When you’re exposed to ultraviolet (UV) light from the sun, your skin uses the sunlight to make the vitamin from scratch.

Most people get enough vitamin D from these two sources. After all, it takes only 5 to 30 minutes of sun exposure a day for your body to make enough of it. But some people choose to take supplements to keep their vitamin D levels at a normal level — especially if they are at risk for deficiency. (We explain who is at risk later in the article.)

What’s the difference between vitamin D2 and vitamin D3?

There are two versions of vitamin D that can be found in supplements: vitamin D2 and vitamin D3. They are slightly different molecules. But your body can absorb both of them, and they both will raise vitamin D levels in the body. Still, there are a few key differences. Before we dive into the details, the chart below summarizes these differences.

It’s important to note that there are many formulations of vitamin D, and some may come in different doses than listed above. 

What is vitamin D2?

Vitamin D2 is also referred to as ergocalciferol. It’s a version of vitamin D that comes from plants and fungi. It’s formed when a specific compound in plants known as ergosterol is exposed to UV radiation from the sun. (Although it’s important to note that the vitamin D2 in supplements is made in a lab.) Foods that are fortified with vitamin D — like dairy products and cereals — usually contain vitamin D2. 

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• Vitamin D dosing: You may need your vitamin D levels checked to know how much vitamin D you need per day.

• Best food sources: One of the best ways to get your vitamin D every day is through foods that are high in vitamin D. 

• Vitamin D deficiency: A low vitamin D level usually doesn’t cause any symptoms. But it can lead to serious long-term health problems.

What is vitamin D3?

Vitamin D3 is also referred to as cholecalciferol. It’s a version of vitamin D that comes from animals. It’s the form that is produced when skin (from humans or animals) is exposed to UV radiation from the sun. It’s also the type of vitamin D that’s naturally found in foods like fish and egg yolks. 

Vitamin D2 vs. D3: Which one is better? 

There was a time when these two forms of vitamin D were thought to be equivalent and interchangeable. But now experts believe this isn’t entirely the case. 

Evidence shows that D2 is actually less effective at raising vitamin D levels, and has a shorter duration of action in the body than its D3 counterpart. D2 also has a shorter shelf life. So while both can be used as a supplement, D3 seems to be slightly superior to vitamin D2.

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Even though D3 seems to be a better option for supplementation, you might be wondering why healthcare professionals prescribe vitamin D2 instead. This is usually based on which form is available in the dosage someone needs. For example, high-dose vitamin D2 is the only form that’s available by prescription. And the size of the dose is going to make a bigger difference than the form of vitamin D. 

Is a prescription required for vitamin D?

Depending on the strength of vitamin D2 or D3 you’re looking for, you may not need a prescription. Formulations that are available over the counter (OTC) usually come in the following doses, which are measured in international units (IU):

• 400 IU 

• 800 IU

• 1,000 IU

• 2,000 IU

• 5,000 IU

If someone has low vitamin D levels, their primary care provider may recommend taking a more concentrated supplement. This is prescription only, because the dose is much higher than OTC options (25,000 IU to 50,000 IU). Someone usually only takes this high of a dose for a short period of time to get their levels back up to a normal range. 

It’s also important to know that while these extra high doses are sometimes used intermittently to boost vitamin D levels, it’s a controversial approach. This is because there has never been strong evidence to show they’re any more effective than smaller, more conservative doses. 

Do I need vitamin D supplements?

There are many different reasons that someone might take vitamin D supplements. The most common reason is because they have low levels of vitamin D. 

People can have low vitamin D levels for a variety of reasons, including:

• Low dietary intake: Most people don’t have a diet rich in liver and mushrooms. Young infants are particularly at risk for low vitamin D levels because of low dietary intake.

• Low sunlight exposure: This is common in winter months and latitudes where sunlight is limited. People who spend most of their time indoors are also at risk for low vitamin D levels.

• Darker skin tone: People with high levels of skin pigmentation make less vitamin D with sun exposure. 

People with certain medical conditions may also need to take vitamin D supplements, often as a preventive measure to help strengthen their bones. Some examples include:

• Rickets: This is a condition in children who have weak bones due to prolonged vitamin D deficiency.

• Adults with osteoporosis: This is a common condition where bones lose their strength. It typically affects people as they age, but tends to be more prevalent in women. 

• Hypoparathyroidism: This happens with low parathyroid hormone (PTH). If you don’t have enough PTH, your calcium levels can drop, which can affect your bone strength. Taking vitamin D can help the body absorb more calcium and strengthen bones.

• Familial hypophosphatemia: This is an inherited condition that results in low levels of phosphate in the blood (which is also important for bone health). Vitamin D helps increase those levels.

Vitamin D recommended daily intake

The recommended dosage for vitamin D varies by age. Experts recommend a daily dose of: 

• 400 IU for infants younger than 12 months

• 600 IU for people between ages 1 and 70

• 800 IU for people who are 71 years and older

As you can see, these doses are far less than the 50,000 IU concentrated supplements often recommended for people with low levels of vitamin D. 

Is too much vitamin D bad for you?

Excessive doses of vitamin D can be harmful. This is because it can lead to abnormally high levels of calcium in the blood, which can cause:

• Nausea, vomiting, or abdominal pain

• Dehydration or excessive thirst

• Kidney stones

• Confusion and hallucinations

• Muscle weakness and lethargy

• Heart arrhythmias

• Kidney failure

If you’re wondering whether you should be taking a vitamin D supplement, it’s best to ask your primary care provider. They can help you understand your personal vitamin D needs. You can also get vitamin D screening and treatment with GoodRx Care.

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Written by:

Katie E. Golden, MD

Katie E. Golden, MD, is a board-certified emergency medicine physician and a medical editor at GoodRx.

Reviewed by:

Karla Robinson, MD

Karla Robinson, MD, is a medical editor for GoodRx. She is a licensed, board-certified family physician with almost 20 years of experience in health through varied clinical, administrative, and educational roles.

Reviewed by:

Stacia Woodcock, PharmD

Stacia Woodcock, PharmD, is a pharmacy editor for GoodRx. She earned her Doctor of Pharmacy degree from the University of Kentucky and is licensed in New York and Massachusetts.

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