Vitamin D intake: Useful information about deficiency and dosage

Vitamin D Einnahme: Nützliche Hinweise über Mangel und Dosierung

Vitamin D is an important vitamin for your body due to its effects on muscles, metabolic control and skeletal mineralization. With regular sunbathing, the vitamin D dose can be replenished daily.

You can find out everything about dosage and deficiency in our guide. If you have signs of a vitamin D deficiency, you should first arrange for a serum test. It is not recommended to order supplements online without consulting your doctor. Many products can lead to overdose.

the essentials in brief

  • Vitamin D is fat soluble. A high-fat meal improves the synthesis of vitamin D.
  • Overdosing when sunbathing is not possible. Excess vitamin D is stored in muscle and fat for the sunless season.
  • 80% of vitamin D is synthesized through the sun. The other 20% comes from food and supplements.

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Definition: What is vitamin D?

Vitamin D is a group of fat-soluble vitamins. This is responsible for your calcium and phosphate metabolism and mineralization of the skeleton. Vitamin D also helps to control genes, protein formation and metabolic processes.

There are two forms of vitamin D: vitamin D3 and vitamin D2. Vitamin D3 is formed independently in the skin and can also be found in cod liver and fish oil. Vitamin D2 is produced biochemically by the body when yeast and mushrooms are consumed(6).

Background: What you should know about vitamin D deficiency and intake

Do you feel tired, lacking in energy and not able to perform as well as you used to? Have you already been to the doctor and he found out you have a vitamin D deficiency? The earlier you find out about vitamin D intake and effects, the better you can control your vitamin D balance yourself.

Woman points in the air

Regularly outside in sunlight, depending on the season and skin type, 10 to 30 minutes help to supply your body with vitamin D. (Source: Jude Beck / unsplash)

In this guide we have put together the most important information about vitamin D deficiency, intake and overdose for you. However, this guide does not replace a visit to the doctor for serious health problems.

What does the body need vitamin D for?

Vitamin D group is responsible for strong bones and muscle strength. An improvement in chronic diseases and in the general circulatory condition are also associated with vitamin D intake. Some observational studies have shown that high blood pressure, type 2 diabetes mellitus and cardiovascular and cancer diseases can be influenced with vitamin D(1).

When are vitamin D products useful?

In old age, in people with strong skin pigmentation, but also in areas with little sun exposure like in Denmark, it is difficult for the body to absorb vitamin D naturally(5). These individuals are advised to access dietary supplements. Your general practitioner will help determine the right dose based on a blood test tailored to this.

How do I recognize a vitamin D deficiency and what are the consequences?

1 billion people worldwide suffer from vitamin D deficiency. Modern lifestyle, which mainly takes place indoors, but also environmental factors severely limit natural sunlight absorption. This is the primary source for the synthesis of vitamin D(6).

There are different risk groups that suffer from a vitamin D deficiency. Location, latitude, position of the sun, season and time of day are factors that affect your vitamin D levels in the body.

  • Regions with little sun strength: Individuals living in high latitudes such as Finland and Sweden.
  • Seniors aged 65 and over: Vitamin D formation decreases with age. People who are bedridden or who spend most of their time at home due to a disability are also particularly at risk of developing vitamin D deficiency.
  • Religious reasons: People with reduced exposure to the sun, for example covering their whole body because of religious beliefs.
  • High skin pigmentation: Due to low solar permeability could cause low sun absorption in the body. People of African, African-Caribbean or South Asian origin need more sunlight than those with lighter skin types so that vitamin D can form better.
  • Pregnant and lactating women, especially teenagers and young women: For good mineralization of the skeleton and successful formation and development of baby bones. Sufficient vitamin D production is necessary for breastfeeding mothers.
  • Infants and children: The most common cause of growth retardation and rickets in infants and children is vitamin D deficiency.
risk group Follow
infants and babies Growth retardation, rickets
Adults with high skin pigmentation, pregnant and lactating women, Muslim, residing in high latitude Cardiovascular diseases, cancer, autoimmune and infectious diseases
Seniors over 65 years Muscle weakness, musculoskeletal pain, osteopenia, osteoporosis, risk of fracture, risk of falling, multiple sclerosis, rheumatoid arthritis, type 1 diabetes mellitus

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In summary, in adults with vitamin D deficiency, these consequences can be mentioned: osteopenia and osteoporosis. These phenomena increase the risk of fracture. The risk of cardiovascular disease, cancer, autoimmune and infectious diseases also increases(3).

A reasonable amount of sun exposure, depending on skin type and sun intensity, is enough for 10 to 30 minutes a day on arms, legs and face to replenish vitamin D levels.

For older people, exposing their arms and legs to the sun wouldn't do as much. In most cases, a diet and supplemental vitamin D intake are prescribed by the doctor(2).

In the elderly, vitamin D deficiency is associated with chronic musculoskeletal pain, muscle weakness, increased risk of falls, multiple sclerosis, rheumatoid arthritis and type 1 diabetes mellitus, and higher incidence of hypertension(6,4)

For this reason, it is necessary to carry out an annual measurement of 25-hydroxyvitamin D (25(OH)D for short) in the blood serum of people at risk.

It is important to be careful not to do the 25(OH)D3 lab test, but to do the complete 25(OH)D. Because the latter gives a more revealing documentation about the status of the serum. In this way, a more accurate prognosis can be made about the treatment(6).

Some reference values ​​are compiled below. However, these are exemplary values. The interpretation of the laboratory values ​​should only be discussed with the doctor performing the test. Deviations from the specified values ​​can occur and do not automatically indicate a disease.

Unit reference range
men up to 18 years Men over 18 years old women up to 18 years women over 18 years of age
nmol/L (nanomoles per liter) 60-120 nmol/L 50-100 nmol/L 60-120 nmol/L 50-100 nmol/L

What happens if you overdose on vitamin D?

If vitamin D is synthesized by the sun, no overdose can occur. In addition, an excess portion of vitamin D is stored in fat and muscle cells for the sun-free season. When taking dietary supplements, it is strongly recommended that you only take preparations prescribed by your doctor.

If you choose your own supplements and take them, you could overdose. The consequences of this are nausea and vomiting, loss of appetite, extreme thirst, increased urination, weakness, headaches, nervousness, kidney stones, kidney damage, kidney calcification and even kidney failure.

Older people may also experience fatigue, confusion and difficulty walking. So it is important to remedy vitamin D deficiency only under medical supervision. Below are some guidelines for taking vitamin D.

risk group Amount of vitamin D taken per day
Children up to 10 years maximum 50 micrograms
Adult no more than 100 micrograms

What supports vitamin D intake?

Together with calcium, vitamin K or fats? What favors better absorption of vitamin D? Research has shown that increased calcium intake, along with an adequate source of vitamin D, plays an important role in maintaining good bone health(1).

woman eats noodles

Numerous studies have shown that fat-soluble vitamins are best absorbed and utilized with a high-fat meal. (Source: Pablo Merchán Montes / unsplash)

No direct correlation between better absorption and vitamin K has been found. On the contrary, there is a higher chance of calcification when calcium, vitamin D and vitamin K are taken together(7).

Numerous studies have shown that fat-soluble vitamins are best absorbed and utilized with a high-fat meal. Unfortunately, no fish oil additive is enough, because the fat content of this is only about 1 gram. The effect is already evident from 15 grams. This corresponds to at least 3 teaspoons of oil.

Even high doses of calcium or calcium infusions alone can ensure bone mineralization(5).

In most meals it's at least 5 grams of fat, which is also the amount of fat in a single egg. As a comparison, a tuna wrap with mayonnaise already contains 40 grams of fat. For example, you can increase absorption by 32% to 57% with additional consumption of a high-fat meal compared to taking it with water.

Vitamin D Intake Dosage: Natural sources and dietary supplements

In this part of our guide you will learn about the natural and synthetic sources of vitamin D. This way you can estimate and pay attention to how much you are getting from food, sun exposure or supplements.

natural sources


Regularly outside in sunlight, depending on the season and skin type, 10 to 30 minutes help to supply your body with vitamin D. According to the Robert Koch Institute, 80 to 90% of vitamin D is formed on the skin through direct sunlight.


10 to a maximum of 20% of the vitamin can be formed through food and dietary supplements. Consumption of fatty fish such as salmon, herring or mackerel is recommended. Liver, egg yolk, and some edible mushrooms are also a source of vitamin D.(5) The following are the most common dietary sources and sources of vitamin D.

Hfood vitamin D content
Oily Fish 4.1 μg per 85 g serving of sardines
cod liver oil 11.3mcg per 5ml
hard boiled egg 1. 1mcg per piece
pork meat 0.2 to 2.56 micrograms per 100 grams
margarine 10.7mcg per 100g
Portobello mushrooms 7.9 µg per 120 mg

dietary supplements

Different dosage forms of vitamin D are presented below.


Drops are one of the best forms of intake for vitamin D. Because the vitamin is dissolved in the oil and is therefore quickly available. Individual and easy dosing also speaks for drops as a dosage form.

Vitamin D Capsules

The second best way to take vitamin D is in capsules. These contain hardly any additives and offer a good absorption of vitamin D. The hard capsules sometimes have a gelatine shell and this is disadvantageous for people who do not eat pork products.

However, there are also variants made of cellulose. The capsules do not contain any oil, so the increase in vitamin D levels cannot be achieved so quickly. However, there is also a special form of vitamin D capsules: soft capsules. These are tightly closed and contain vitamin D oil or gel. Here the vitamin D increase in serum is comparable to that of the oil.

Vitamin D tablets

The last vitamin D dosage form is tablets. These contain some additives due to production. These are harmless, but reduce the purity of the product. The usability of vitamin D in this form is low and vitamin D levels rise imperceptibly. When buying vitamin D supplements, pay attention to the following:

  • Active ingredient: vegan or animal
  • Combination preparation and bioavailability: calcium and oil, for better absorption and utilization
  • Dosage: observe the maximum recommended amount associated with age
  • Dosage form: liquid (oil, soft capsule) or solid (hard capsule, tablets)
  • Ingredients: few additives (free from gluten, lactose and gelatine) guarantee the purity of the product
  • fertility


It is recommended to let the sun shine on your arms, face and legs for 10 to 30 minutes every day, depending on your skin type. This is for the natural availability and synthesis of vitamin D. Dietary supplements are only recommended for people who cannot synthesize vitamin D from sun or food.

Older people over the age of 65, people in areas with little solar radiation and veiled Muslim women are most affected.

Before making any assumptions about vitamin D deficiency, a doctor should be consulted. After a complete 25(OH)D test, the vitamin D level in serum can be determined.


  1. Holick MF. Vitamin D and bone health. J Nutr. 1996;126(4 Suppl):1159S-64S. doi:10.1093/jn/126.suppl_4.1159S
  2. Holick MF. Sunlight and vitamin D for bone health and prevention of autoimmune diseases, cancers, and cardiovascular disease. Am J Clin Nutr. 2004;80(6 Suppl):1678S-88S. doi:10.1093/ajcn/80.6.1678S
  3. Holick MF. Sunlight, ultraviolet radiation, vitamin D and skin cancer: how much sunlight do we need?. Adv Exp Med Biol. 2014;810:1-16
  4. Holick MF. Evolution and function of vitamin D. Recent Results Cancer Res. 2003;164:3-28. doi:10.1007/978-3-642-55580-0_1
  5. Lips P. Vitamin D physiology. Prog Biophys Mol Biol. 2006;92(1):4-8. doi:10.1016/j.pbiomolbio.2006.02.016
  6. Charoenngam N, Shirvani A, Holick MF. Vitamin D for skeletal and non-skeletal health: What we should know. J Clin Orthop Trauma. 2019;10(6):1082-1093. doi:10.1016/j.jcot.2019.07.004
  7. The Synergistic Interplay between Vitamins D and K for Bone and Cardiovascular Health: A Narrative Review. 2017 Adriana J van Ballegooijen, Stefan Pilz, Andreas Tomaschitz, Martin R Grübler, Nicolas Verheyen
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