Vitamin D3, also known as cholecalciferol, is one of two types of vitamin D. It differs from the other type, called vitamin D2 (ergocalciferol), by both its molecular structure and sources.

Vitamin D3 is found in certain foods such as fish, beef liver, eggs, and cheese. It can also be produced in the skin following exposure to ultraviolet (UV) radiation from the sun.

In addition, vitamin D3 is available as a dietary supplement where it is used for general health or for the treatment or prevention of vitamin D deficiency. Some manufacturers of fruit juices, dairy products, margarine, and plant-based milk add vitamin D3 to boost their product’s nutritional value.

The article explains what vitamin D supplements do as well as the benefits and drawbacks of vitamin D3 specifically. It also lists other important sources of vitamin D3 beyond pills.

What Is Vitamin D Deficiency?

Vitamin D, also referred to as calciferol, is a fat-soluble vitamin (meaning one that is broken down by fat and oils in the gut). It is commonly referred to as the “sunshine vitamin” because it can be naturally produced in the body following exposure to the sun.

Vitamin D has many functions in the body, chief of which include bone growth, bone remodeling, the regulation of muscle contractions, and the conversion of blood glucose (sugar) into energy.

When you do not obtain enough vitamin D to meet the body’s needs, you are said to have vitamin D deficiency.

Causes for vitamin D deficiency are many, including diseases or conditions that limit fat absorption and the breakdown of vitamin D in the gut.

Consequences of Vitamin D Deficiency

Vitamin D deficiency can lead to an array of health concerns, including delayed growth and rickets in kids, osteomalacia (loss of bone minerals) in adults and adolescents, and osteoporosis (porous, thinning bones) in adults.

Common causes of vitamin D deficiency include:

  • Celiac disease
  • Crohn’s disease
  • Cystic fibrosis
  • Gastric bypass surgery
  • Liver disease
  • Malnutrition
  • Obesity
  • Ulcerative colitis

People who are older, are housebound, or have dark skin are also more vulnerable to vitamin D deficiency.

Why Vitamin D3?

Vitamin D supplements can be used when a person does not obtain enough vitamin D through food or sun exposure. There are two forms—vitamin D2 and vitamin D3—each of which has its benefits and drawbacks.

Screening Recommendations

The U.S. Preventive Services Task Force does not recommend routine vitamin D screening in adults without symptoms of deficiency. If you suspect you are vitamin D deficient, ask your healthcare provider to test your blood levels.

Vitamin D2 and vitamin D3 are chemically similar and are both well-absorbed in the gut. Where they differ significantly is in their sources:

  • Vitamin D2 is naturally found in mushrooms, including shiitake, portobello, and crimini mushrooms. The vitamin D content increases when these mushrooms are exposed to UV radiation.Vitamin D3 is naturally found in animals and animal-derived products like milk. It is also directly synthesized in the skin when it is exposed to ultraviolet B (UVB) radiation.

Another way that vitamin D3 differs from vitamin D2 is in its bioavailability (the proportion of a drug that enters the bloodstream) and half-life (a measure of the amount of time a drug stays in circulation).

In both respects, vitamin D3 has proven superior to vitamin D2,

On the downside, vitamin D3 in supplements has historically been synthesized using lanolin derived from sheep’s wool. This makes it unsuitable for strict vegans or vegetarians.

Effectiveness of Vitamin D3

Not only does vitamin D3 stay in the body longer, but some studies suggest that it also raises the vitamin D level in the bloodstream 87% more than vitamin D2.

With that said, in recent years some manufacturers have been able to synthesize vitamin D3 from algae and lichen. So, if you decide to buy a vitamin D3 supplement, read the product label carefully to ensure that it is vegan-friendly.

Health Benefits of Vitamin D3

Vitamin D deficiency affects almost 50% of the population worldwide. Both vitamin D2 and D3 can be used to treat this, with vitamin D3 generally being the preferred choice.

Beyond its use in treating vitamin D deficiency, vitamin D3 may offer health benefits to certain people without such deficiency.

Hypertension

Hypertension, more commonly known as high blood pressure, is cardiovascular disease commonly seen in people with vitamin D deficiency.

Recent studies suggest that vitamin D3 may help lower blood pressure in people with hypertension and vitamin D deficiency as well as certain groups of people with hypertension only.

According to a 2019 review of studies in the journal Medicine involving 1,687 people, vitamin D3 was able to significantly reduce systolic (upper) blood pressure in people over the age of 50 as well as those with obesity.

This is important because isolated systolic hypertension can over time increase the risk of stroke, heart disease, and chronic kidney disease.

Osteoporosis

Osteoporosis is a frequent consequence of long-term vitamin D deficiency, and common wisdom would suggest that vitamin D supplements may help prevent (or slow the progression of) this common aging-related bone disease. There is some evidence to support this claim.

A 2013 study from the University of Western Australia found that the use of vitamin D3 in nursing home residents aged 70 and over significantly reduced the incidence of hip fractures. In addition, low-dose vitamin D3 (400 IU) also increased bone mass density in the femoral (thigh) bone.

Sources of Vitamin D3

Whether you are nutritionally deficient or simply want to meet your recommended daily allowance (RDA) of vitamin D, you obtain ample supplies of vitamin D3 from animal-based foods, dietary supplements, and the sun.

Unproven Benefits

Despite claims to the contrary, there is no evidence that vitamin D3 supplements can reduce the risk of cancer, coronary heart disease, or stroke. With that said, the supplements pose little, if any, harm if taken at the prescribed dose.

Current guidelines from the National Institutes of Health recommend that people ages one to 70 should get 600 (international units) IUs of vitamin D per day from all sources. Adults over 70 need 800 IUs daily.

Dietary Sources

Food should always be the first source of vitamin D. Here are some of the best dietary sources of vitamin D3 to bolster your intake:

Supplements

As convenient as they are, supplements should never be your primary source of vitamin D (or any nutrient for that matter). They are really only intended for when you are not getting enough from your diet.

Vitamin D3 is readily available in supplement form and sold as capsules, soft gels, gummies, and liquid drops. Most are formulated in doses higher than you need per day—between 2,000 and 10,000 IUs—but this is not a concern as only a portion will be absorbed and the rest will be passed in urine.

Talk to your healthcare provider about the best dose for you based on your age and medical history. And, as a general rule, never exceed the dose listed on the product label.

Sun Exposure

Vitamin D3 is unique in that (unlike vitamin D2) you can get it from the sun.

When exposed to UVB light, an organic compound in the skin called 7-dehydrocholesterol will activate and start churning out vitamin D3. The rate of production can vary by your age and skin tone (with older people and those with darker skin getting the least benefit). Sunscreen can also decrease production by blocking both UV rays.

Getting a little sunlight every day can help you maintain your vitamin D levels, but it’s not the safest or most reliable way to get it given the risk of skin cancer.

Possible Risks

Vitamin D3 is generally regarded as safe, but it can on rare occasions cause toxic effects if you take too much. This is referred to as hypervitaminosis D.

With vitamin D toxicity, the balance of minerals like calcium and potassium will be upset. This can lead to a condition known as hypercalcemia where too much calcium builds up in the body, leading to symptoms like:

  • Stomach upsetNauseaVomitingConstipationBone painMuscle weaknessAn increased risk of bone fractures

Vitamin D toxicity was common in the 1940s when daily doses of 200,000 to 300,000 IUs per day were commonly recommended to treat chronic illnesses like tuberculosis and rheumatoid arthritis.

Today, vitamin D toxicity is considered a rare occurrence.

Recent studies have shown that vitamin D3 doses of 20,000 IUs per day are tolerable in adults with no signs of toxicity.

Summary

Vitamin D helps you absorb calcium and phosphate from food. Vitamin D3 is more efficient than D2. You get vitamin D from food, supplements, and sunshine.

Vitamin D is important for bone and muscle strength and immune function. It may help prevent depression, inflammatory disease, and heart disorders.

Adults under 70 should get 600 IU a day. Older adults should get 800 IU. Supplements are the most reliable way to get enough vitamin D.

Taking too much can have toxic effects. Have your healthcare provider test your levels before starting a supplement.

A Word From Verywell

If you have health conditions that could be tied to vitamin D, bring it up with your healthcare provider. It’s easy to boost levels with supplements. And that could mean feeling a lot better and being healthier down the road.

Frequently Asked Questions

  • When should I take vitamin D3?
  • Vitamin D3 is a fat-soluble vitamin. This means that taking it with fat helps it absorb better. It doesn’t matter what time of day you take it, but you should eat fat-containing food when you do.
  • Learn More:
  • What Is a Fat Soluble Vitamin?
  • How can I check my vitamin D levels at home?
  • There are some mail-in home tests (from companies like Everlywell, Drop, and myLAB Box) that can measure the amount of vitamin D in your blood. All you need to do is place a drop of blood on a test strip and mail it to the test manufacturer for results.
  • Learn More:
  • What to Know About Vitamin D Home Tests
  • Does vitamin D3 give you energy?
  • A lack of vitamin D can cause you to feel lethargic. So if you’re deficient, taking D3 supplements could, over time, help you feel more energetic. However, D3 supplements don’t provide an immediate energy boost. They won’t reduce fatigue unless you have a deficiency.
  • Learn More:
  • Vitamin D Deficiency and Headaches
  • Who should not take vitamin D3?
  • People with hyperparathyroidism, kidney disease, or hypercalcemia (high blood calcium) typically avoid vitamin D3 supplements. Certain medications can also interact with vitamin D including Alli (orlistat), prednisone, and thiazide diuretics. Speak with your doctor to ensure that vitamin D is safe for you and does not interfere with any medication you are one.

Vitamin D3 is a fat-soluble vitamin. This means that taking it with fat helps it absorb better. It doesn’t matter what time of day you take it, but you should eat fat-containing food when you do.

There are some mail-in home tests (from companies like Everlywell, Drop, and myLAB Box) that can measure the amount of vitamin D in your blood. All you need to do is place a drop of blood on a test strip and mail it to the test manufacturer for results.

A lack of vitamin D can cause you to feel lethargic. So if you’re deficient, taking D3 supplements could, over time, help you feel more energetic. However, D3 supplements don’t provide an immediate energy boost. They won’t reduce fatigue unless you have a deficiency.

People with hyperparathyroidism, kidney disease, or hypercalcemia (high blood calcium) typically avoid vitamin D3 supplements. Certain medications can also interact with vitamin D including Alli (orlistat), prednisone, and thiazide diuretics. Speak with your doctor to ensure that vitamin D is safe for you and does not interfere with any medication you are one. 

  • National Institutes of Health Office of Dietary Supplements. Vitamin D: fact sheet for health professionals.

  • US Preventive Services Task Force, et al. Screening for vitamin D deficiency in adults: US Preventive Services Task Force recommendation statement. JAMA. 2021;325(14):1436-1442. doi:10.1001/jama.2021.3069

  • MedlinePlus. Cholecalciferol (vitamin D3).

  • Tripkovic L, Lambert H, Hart K, et al. Comparison of vitamin D2 and vitamin D3 supplementation in raising serum 25-hydroxyvitamin D status: a systematic review and meta-analysis. Am J Clin Nutr. 2012 Jun;95(6):1357–64. doi:10.3945/ajcn.111.031070

  • Nair R, Maseeh A. Vitamin D: the “sunshine” vitamin. J Pharmacol Pharmacother. 2012 Apr-Jun;3(2):118–26. doi:10.4103/0976-500X.95506

  • He S, Hao X. The effect of vitamin D3 on blood pressure in people with vitamin D deficiency: a system review and meta-analysis. Medicine (Baltimore). 2019 May;98(19):e15284. doi:10.1097/MD.0000000000015284

  • Geddes JAA, Inderjeeth CA. Evidence for the treatment of osteoporosis with vitamin D in residential care and in the community dwelling elderly. Biomed Res Int. 2013;2013:463589. doi:10.1155/2013/463589

  • Danik JS, Manson JE. Vitamin D and cardiovascular disease. Curr Treat Options Cardiovasc Med. 2012 Aug;14(4):414–24. doi:10.1007/s11936-012-0183-8

  • Marcinowska-Suchowierska E, Kupisz-Urbańska M, Łukaszkiewicz J, Płudowsk P, Jones G. Vitamin D toxicity–a clinical perspective. Front Endocrinol (Lausanne). 2018;9:550. doi:10.3389/fendo.2018.00550

  • Nowak A, Boesch L, Andres E, et al. Effect of vitamin D3 on self-perceived fatigue: A double-blind randomized placebo-controlled trial. Medicine (Baltimore). 2016;95(52):e5353. doi:10.1097/MD.0000000000005353

  • National Institutes of Health, Office of Dietary Supplements. Vitamin D fact sheet for consumers.

By Yvelette Stines

Yvelette Stines, MS, MEd, is an author, writer, and communications specialist specializing in health and wellness.