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The #1 Best Vitamin D Supplement to Take, Says Dietitian

There are actually many different types of vitamin D supplements you can take—according to one dietitian, this kind is the best.
FACT CHECKED BY Olivia Tarantino

The effects of low vitamin D levels can be wide-ranging. Fatigue, bone pain, muscle weakness or cramps, and mood changes are just a few of the signs that you might have a vitamin D deficiency. At the same time, surprising benefits of taking vitamin D supplements, like immune system support and lower blood pressure, have been well documented.

While exposure to the sun and a healthy diet can help you produce vitamin D in your body, many of us would benefit from supplements to help increase our levels. But with a wide range of different vitamin D supplements available on the market, the options can seem overwhelming.

Read on to learn what to know about vitamin D supplements, specifically, calcifediol—the best form of vitamin D you can take, and for more on how to eat healthy, don't miss Surprising Side Effects of Not Taking Vitamin D Supplements, Says Dietitian.

Not all vitamin D is the same.

vitamin d pills

The two forms of vitamin D that many people may be most familiar with are vitamin D2 (ergocalciferol), derived from yeast or mushrooms, and vitamin D3 (cholecalciferol), derived from animal sources like fish and egg yolks. There's another form, though, called calcifediol.

Calcifediol is produced when D3 is metabolized by the liver and is the form of vitamin D that circulates in your bloodstream. We often don't get enough of it through diet and from the sun, and most vitamin D supplements on the market do not provide calcifediol directly—they either contain vitamin D2 or vitamin D3, which must be processed by the liver to create the vitamin D that then circulates in the blood.

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The vitamin D supplement, calcifediol, is the best type of vitamin D supplement because it raises blood vitamin D levels fast.

vitamin d

Since a calcifediol supplement does not need to be processed by the liver, it can be absorbed directly into the bloodstream and throughout your body, which makes a calcifediol supplement three times more effective in raising vitamin D levels when compared to vitamin D3 on an equal microgram (mcg) basis. When taking a supplement with calcifediol, you could reach your recommended levels of vitamin D in days instead of months, when compared to vitamin D2 or vitamin D3 supplements.

What's more, several factors can directly affect an individual's vitamin D status, including body weight. Because vitamin D is a fat-soluble vitamin, it can get trapped in fat tissue. Calcifediol is less likely to be affected by body fat because it is less fat-soluble. Research has shown that individuals with higher body weight may benefit from using calcifediol as a source of vitamin D.

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You need a test to know your Vitamin D levels.

vitamin d supplements

Aside from the different forms of vitamin D, it can also be confusing to know how much you need.

The National Institutes of Health offers recommendations on how much vitamin D you need each day based on your age, but the daily upper limit for vitamin D for adults is 4,000 IU. If your total intake of vitamin D is below this level, there is no difference in safety between taking the different forms.

The only way to know what your vitamin D levels are, is through a blood test. It is a good idea to have your vitamin D levels tested regularly, especially if you're taking supplements to understand if they are working and ensure that you're not getting too much. This can be done either with a reliable at-home test kit or by requesting a vitamin D test during your annual physical. Most laboratory tests report total 25-hydroxyvitamin D (calcifediol) as the reference measure of vitamin D status in the body. This includes both vitamin D2 and vitamin D3 forms because they both contribute to vitamin D status.

READ MORE: 5 Signs of Vitamin D Deficiency You Should Never Ignore


woman taking fish oil
Shutterstock / blackzheep

Vitamin D is an important nutrient that is hard for many people to get enough of, either from the sun or from their typical diet. Because of this, vitamin D supplements can be a good option. Taking a vitamin D supplement regularly can help you achieve ideal levels, especially in the fall and winter.

Disclaimer: Melissa Rifkin, MS, RD, CDN is a New York dietitian who specializes in weight management and bariatrics, and a spokesperson for health company Hologram Sciences.

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Melissa Rifkin, MS, RDN, CDN
Melissa is a Connecticut-based registered dietitian with over 15 years of experience, including clinical and outpatient settings, and runs the popular nutrition education Instagram account, Confessionofadietitian. Read more about Melissa