• The biggest mistake you’re making is choosing the wrong form of vitamin D supplement. 
  • Vitamin D3 is from animals, and it is the type you make from the sun, which is absorbed better.
  • Choose an independently-tested supplement or add fatty fish and fortified foods to your diet. 

You might be doing everything right—taking a vitamin D supplement, drinking milk, eating salmon and soaking up midday rays. On the surface, it seems like you’ve got your vitamin D bases covered. Yet almost 25% of people in the United States are running low. Vitamin D plays far more roles in the body than you may realize.

“While its claim to fame is often associated with the role it plays in protecting bone health through helping the body absorb calcium, that’s not all you need vitamin D for,” says Elizabeth Shaw, M.S., RDN, CPT. “It’s also involved in communication in the body, muscle movement and immune health. In fact, you need vitamin D to help kick free radicals out of your body, like the common cold and flu, so you can stay healthy.”

Even if you’re taking a vitamin D supplement like clockwork every day, you still might not be absorbing enough.  According to experts, the biggest mistake people are making is choosing the wrong form of vitamin D. So, which one should you be choosing? Here, we break down the differences between the two types of vitamin D and which one you should be reaching for. 

The Difference Between Vitamin D2 and D3

When you look at vitamin D supplements options, you may notice two forms available: vitamin D2 and vitamin D3. While both can help raise and maintain vitamin D levels, they come from different sources and your body utilizes them differently. Below we explore what sets the two apart. 

Vitamin D2

Vitamin D2, also known by its scientific name ergocalciferol, comes primarily from plant-based sources. “Vitamin D2 is photosynthesized in plants, mushrooms and yeasts. In other words, mushrooms exposed to sunlight synthesize vitamin D2,” explains Holli Ryan, RD, LD.

Both D2 and D3 must undergo two steps to become biologically active: first, conversion in the liver, then again in the kidney. However, once activated, research shows that vitamin D3 is more effective at raising and maintaining 25(OH)D levels, which is your blood serum vitamin D status. Vitamin D2 has structural differences that reduce its ability to bind to vitamin D-binding protein, and it also breaks down more quickly. Its shorter half-life means it doesn’t stay in your system as long either. Ultimately, making it the less-than-desirable option. 

Vitamin D3 

Vitamin D3, also known as cholecalciferol, is found in animal-based foods such as salmon, tuna, herring, egg yolks, and cheese, as well as in fortified foods like dairy milk and orange juice. It’s also the form your body naturally produces when you get some rays. “Vitamin D3 is closer to the form your body naturally makes from sunlight, so it’s more efficient at supporting and maintaining vitamin D levels,” explains Bonnie Taub-Dix, RDN.

Although the body can use both forms of vitamin D, studies show that vitamin D3 can raise blood levels of vitamin D higher and for longer than vitamin D2, says Shaw. In fact, guidelines indicate that vitamin D3 is approximately five times more potent at raising serum 25(OH)D concentrations, compared to D2.

Why Choosing D3 Matters

With nearly 5% of the population at risk of vitamin D deficiency and another 18% with insufficient levels, maintaining adequate levels is a widespread problem. Vitamin D plays multiple critical roles in health, from supporting strong bones to bolstering immune health to aiding with muscle movement. When levels run low, it may lead to weakened immunity, fatigue, or low mood. That’s why choosing the right form of vitamin D is so important. 

How to Choose the Right Vitamin D Supplement

Here are a few expert-backed tips to help guide you towards picking up the right vitamin D supplement.  

  • Look for independently tested brands: Start by choosing a supplement verified by a trusted independent testing organization. “Labels from testing organizations, like NSF certified or USP, mean you know what’s on the label is in the bottle,” says Shaw. This helps ensure you’re choosing a safe, high-quality option.
  • Choose D3: Check that the supplement is in D3 form. “It should read ‘cholecalciferol’ if it has the D3 form,” Shaw points out.  
  • Find vegan-friendly D3: If you’re vegan, look for an algae-derived vitamin D3 supplement, since most D3 supplements are derived from lanolin (sheep’s wool), says Ryan. 
  • Pick a form you’ll take consistently: Softgels and liquid drops are both good options; choose the form you’ll take most comfortably and consistently, advises Taub-Dix. And “check with your healthcare provider to determine what dose is right for you,” she adds.
  • Pair it with fat in your diet: Once you’ve found a tried and true supplement, don’t forget to pair it with fat. “Because vitamin D is fat-soluble, I always remind people to pair these foods with a source of healthy fat to support absorption,” says Shaw. 

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Other Ways to Get Vitamin D

In addition to choosing the right vitamin D supplement, your diet, beverage choices and scheduling in sunshine time can help you boost your vitamin D levels too. 

  • Dive into fatty fish: Salmon, trout, sardines, herring and tuna are all natural sources of vitamin D. 
  • Eat the whole egg: The yolk contains several nutrients, including vitamin D.  
  • Try wild or UVB-treated mushrooms: Wild mushrooms naturally contain vitamin D2 and UVB-treated varieties can contain high amounts of vitamin D too. 
  • Drink milk: Dairy milk is typically fortified with vitamin D. Plant-based milks may also be fortified – check the label.
  • Choose fortified cereals: Many ready-to-eat breakfast cereals contain added vitamin D. Look for it on the nutrition facts panel.  
  • Grab a glass of OJ: Drinking 100% fortified orange juice can give you not only vitamin D but also calcium. (2,5)
  • Schedule sunlight time: While sunlight is a free and natural way to get vitamin D, several variables can make it challenging to rely on alone. Age, skin pigmentation, geographical location, sunscreen use, body fat percentage and the season all affect how much vitamin D your skin produces, says Ryan. “Exposing your skin to UVB rays from the sunlight for around 15 minutes daily without sunscreen can be helpful, but be sure to avoid excessive sun exposure without protecting your skin”.

Monitor your levels regularly with a blood test to ensure you are maintaining adequate vitamin D levels. 

Our Expert Take

The number one mistake people make when taking vitamin D is choosing the wrong form. Experts recommend selecting a vitamin D3 supplement over D2 for maximum benefit and absorption. Research states vitamin D3 is five times more potent than vitamin D2, and more effective at raising and maintaining blood vitamin D levels. 

When picking out a supplement, make sure it’s independently tested, contains the D3 form, and comes in either soft or drop form. Other ways to boost your vitamin D levels are by eating fatty fish, mushrooms or drinking fortified milk or orange juice. Aim for at least 15 minutes of sunlight exposure a day. And don’t forget to monitor your vitamin D levels annually, as vitamin D plays a role in whole-body health.