High-dose vitamin D3: the most important questions and answers

Hochdosiertes Vitamin D3 : Die wichtigsten Fragen und Antworten

Vitamin D3 is obtained through exposure to the sun, diet, or even supplements. High-dose vitamin D3 is taken when there is an insufficient supply of vitamin D in order to regulate the requirement or even alleviate symptoms of certain diseases.

The following article will answer the most important questions about vitamin D3 in high doses . We hope that we have summarized the most important facts and answers to your questions about high-dose vitamin D3 in this article. We hope you enjoy reading!

the essentials in brief

  • Around 80 - 90% of vitamin D3 is produced by the body itself through sufficient solar radiation. As a result, vitamin D3 is also referred to as a hormone.
  • The human body stores vitamin D3 for months, so daily intake is not absolutely necessary.
  • An overdose of high-dose vitamin D3 is associated with numerous side effects, which in the worst case can lead to death.

The most important questions and everything you should know about high-dose vitamin D3

Intake of high doses of vitamin D3 is important to improve resistance to infection, improve immune health and prevent autoimmunity (1).

We have summarized the most important questions and everything you need to know about the topic "vitamin D3 high doses" here.

What is vitamin D3?

Vitamin D is the generic term for the group of fat-soluble vitamins, which includes vitamin D1, vitamin D2, vitamin D3, vitamin D4 and vitamin D5. If one speaks of vitamin D, this is usually associated with vitamin D3. Vitamin D3 is the natural vitamin that is produced by the human body with the help of solar radiation.

woman sunbathes

Unlike other vitamins, vitamin D can be synthesized by the human body itself when exposed to sunlight. (Image Source: Amy Humphries / unsplash)

The artificially produced vitamins include vitamin D1, vitamin D2, vitamin D4 and vitamin D5.

Around 80-90% of vitamin D is produced by the body itself through sufficient exposure to the sun, whereas diet contributes only 10-20%.

Thus, vitamin D3 is more commonly referred to as a hormone (precursor hormone), which the body converts into a hormone called calcitriol (2).

How much vitamin D3 should you take per day?

Depending on the age group, a different intake of vitamin D3 is recommended in the absence of endogenous synthesis . The German Society for Nutrition (DGE) estimates the vitamin D requirement as follows:

Old Vitamin D in µg per day
Infants (0-12 months) 10
Children (1-15 years) 20
Adolescents and adults (15-65 years) 20
Adults (from 65 years) 20
Pregnant and lactating women 20

However, the recommended intake of vitamin D varies from person to person and should be discussed with your trusted doctor.

When is vitamin D3 considered high dose?

When it comes to dosing vitamin D3, a distinction is made between a low dose , a medium dose and a high dose .

Here you have an overview of the classification of the different dosages of vitamin D3:

dose Supply of vitamin D3
low dose 400-1000 units/day
Medium dose 2000-6000 units/day
highly dosed 7000-10000 units/day, 20000-60000 units/week, 100000-200000 units/single dose

High-dose vitamin D is used, among other things, to treat diseases that are explained in the next section.

For whom is taking high-dose vitamin D3 suitable?

Since the body forms vitamin D3 itself with the help of solar radiation and thus 80-90% of the requirement is covered, vitamin D3 preparations should only be used in exceptional cases. For example, taking vitamin D3 supplements makes sense if you are bedridden.

Taking high-dose vitamin D3 is also suitable in the following situations:

type of therapy Description
initial therapy In the initial therapy, vitamin D3 is used to remedy the vitamin D deficiency in the shortest possible time (3).
maintenance therapy In clinics, high-dose vitamin D is used as a weekly or even monthly dose in maintenance therapy. This ensures that patients do not forget to take their daily intake and make ongoing studies useless.
therapy of serious diseases High doses of vitamin D help treat serious diseases such as multiple sclerosis and reduce the symptoms of this disease (4).

However, in cases of therapy for serious illnesses, high doses of vitamin D3 should only be taken under the supervision of a doctor, so that an overdose and the associated consequences can be avoided.

How long can you take high-dose vitamin D3?

The intake of high-dose vitamin D3 is mainly recommended when an insufficient supply of vitamin D3 in the body has been proven. As a result, taking vitamin D3 is a good idea if neither food nor sunlight has been able to confirm an improvement in the supply of vitamin D3 in the body.


Herring has a high vitamin D content and is considered a good alternative to a good supply of vitamin D in the body. (Image Source: Camila Igisk / Unsplash)

High-dose vitamin D3 should generally only be taken as long as the requirement is met.

Is taking high doses of vitamin D3 harmful?

High-dose vitamin D3 is often used to treat diseases. However, this is usually done under medical supervision.

An overdose of vitamin D3 can lead to numerous side effects.

Thus, an excessive intake of high-dose vitamin D3 preparations is associated with harmful consequences, ranging from nausea to, in the worst case, death. We have listed the most common side effects and the resulting consequences of an overdose of high-dose vitamin D3 in the next section. However, these are not all side effects that can arise from an overdose of vitamin D3.

What side effects can occur when taking high-dose vitamin D3?

Vitamin D3 overdose is associated with some side effects. The most well-known side effects are as follows:

  • nausea
  • fatigue
  • hypercalcemia
  • loss of appetite
  • depressions
  • Stomach cramps
  • Vomit
  • kidney damage
  • cardiac arrhythmia
  • unconsciousness
  • Death


When taking vitamin D3, regular visits to a doctor are necessary to avoid overdose and its side effects, which can also be fatal.

Which preparations of high-dose vitamin D3 are there?

Vitamin D3 can be purchased in different preparations. In addition, these can be vegan, organic or plant-based, so that everyone can find the right preparation for themselves.

  • drops
  • tablets
  • capsules
  • oil

When choosing the preparation, it depends on your personal feelings. Some find it difficult to swallow tablets and capsules and prefer to choose the liquid version, such as drops and oil.

Where can you buy high-dose vitamin D3?

The question of buying high-dose vitamin D3 is more difficult. Basically, you can buy high-dose vitamin D3 on the following sites/shops:

  • Amazon.de
  • Various online pharmacies
  • pharmacies

Depending on the preparation and dose, you can only purchase high-dose vitamin D3 with a prescription. Generally speaking, you can purchase high-dose vitamin D3 up to 1000 units of vitamin D over the counter.

Oil, drops and capsules are usually offered with 20,000 units of vitamin D and require a prescription in any case. However, this information only applies to medicinal products. There is no maximum amount specified for dietary supplements, so even a high dose can be purchased without a prescription.

What should you consider when taking high-dose vitamin D3?

As you have already learned in the article, high-dose vitamin D3 is associated with many side effects. Therefore, you should take enough time with your doctor to get the best possible and technically correct information from him. Only doctors who are knowledgeable in this field can tell you exactly how much vitamin D3 is suitable for your body.

However, you should generally note that taking vitamin D3 supplements is independent of the time of day.

Since vitamin D3 is a fat-soluble vitamin, a vitamin D supplement should be taken with a meal as this improves absorption (7).

How quickly do high doses of vitamin D3 break down in your body?

Vitamin D3 is usually stored in our body for months because it is not broken down immediately. Vitamin D3 is stored in fat and muscle tissue and partly in the liver.

So you can't take vitamin D3 for months and still be well supplied with it. Nevertheless, the rate at which vitamin D3 is broken down varies from person to person and cannot be generalized.

What alternatives are there to high-dose vitamin D3?

High-dose vitamin D3 is taken in the form of different preparations and is intended to help people with insufficient coverage of the vitamin D content. However, not everyone wants to take medication and tries to meet their vitamin D needs through other methods. There are two known ways to meet individual vitamin D requirements:

  1. Sun: When exposed to sunlight, the body can produce vitamin D on its own. Therefore, it is best to sunbathe for 15-30 minutes on warm days to adequately cover the vitamin D requirement. In general, the time should not be exceeded so that sunburn can be avoided. Applying sunscreen interferes with vitamin D absorption, so you really shouldn't sunbathe for more than 30 minutes without sunscreen.
  • Diet: Vitamin D is also found in many foods. You can choose from both animal and plant-based foods that are rich in vitamin D. For example, the highest vitamin D content is measured in sea animals(8). To be precise, herring has a vitamin D content of 25 micrograms per 100 grams. In addition to seafood, vitamin D is also found in the following foods: dairy products, meat, eggs, fruit, vegetables and fats such as butter.

Vitamin D deficiency can be remedied through exposure to the sun and diet. However, these types of vitamin D recovery involve a slight increase in your body's vitamin D levels. The vitamin D content in the body cannot be reached by far from the sun and diet as with the intake of high-dose vitamin D3.


Vitamin D3 makes an important contribution to the human immune system. High-dose vitamin D3 is not only offered to remedy a vitamin deficiency, but also in numerous therapies.

However, high doses of vitamin D3 are associated with fatal side effects. Therefore, the dosage should only be discussed in urgent cases and if possible with a doctor of your choice. In any case, you should seek personal advice from a doctor who will draw your attention to the risks and side effects.


  1. Vanherwegen AS, Gysemans C, Mathieu C. Regulation of Immune Function by Vitamin D and Its Use in Diseases of Immunity. Endocrinol Metab Clin North Am. 2017;46(4):1061-1094. doi:10.1016/j.ecl.2017.07.010
  2. Holick MF, Smith E, Pincus S. Skin as the site of vitamin D synthesis and target tissue for 1,25-dihydroxyvitamin D3. Use of calcitriol (1,25-dihydroxyvitamin D3) for treatment of psoriasis. Arch Dermatol. 1987;123(12):1677-1683a.
  3. Wilson LR, Tripkovic L, Hart KH, Lanham-New SA. Vitamin D deficiency as a public health issue: using vitamin D2 or vitamin D3 in future fortification strategies. Proc Nutr Soc. 2017;76(3):392-399. doi:10.1017/S0029665117000349
  4. Kouchaki E, Afarini M, Abolhassani J, et al. High-dose ω-3 Fatty Acid Plus Vitamin D3 Supplementation Affects Clinical Symptoms and Metabolic Status of Patients with Multiple Sclerosis: A Randomized Controlled Clinical Trial. J Nutr. 2018;148(8):1380-1386. doi:10.1093/jn/nxy116
  5. Beer TM, Javle MM, Ryan CW, et al. Phase I study of weekly DN-101, a new formulation of calcitriol, in patients with cancer. Cancer Chemother Pharmacol. 2007;59(5):581-587. doi:10.1007/s00280-006-0299-1
  6. Peterson ME, Fluegeman K. Cholecalciferol. Top Companion Anim Med. 2013;28(1):24-27. doi:10.1053/j.tcam.2013.03.006
  7. Silva MC, Furlanetto TW. Intestinal absorption of vitamin D: a systematic review. Nutr Rev. 2018;76(1):60-76. doi:10.1093/nutrit/nux034
  8. Guo J, Lovegrove JA, Givens DI. 25(OH)D3-enriched or fortified foods are more efficient at tackling inadequate vitamin D status than vitamin D3. Proc Nutr Soc. 2018;77(3):282-291. doi:10.1017/S0029665117004062
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