Vitamin D deficiency is widespread in Germany, while the market for vitamin D supplements remains confusing and hard to navigate. This article reviews the current state of research, clarifies meaningful dosages and explains how the vitamin D complex next d-complete from nextvital fits into this picture.

You will find solid, evidence-based guidance and answers to 20 common questions about vitamin D, vitamin D deficiency and the practical use of next d-complete.

Vitamin D Deficiency in Germany: The Scale of the Problem

Around 15% of German adults have vitamin D levels below 30 nmol/l (25(OH)D) - a range associated with an increased risk of overt deficiency. Only about 44% reach the concentration of at least 50 nmol/l which is considered desirable.

The German Nutrition Society (DGE) confirms: Overall, the population's vitamin D status is inadequate.

Key points on vitamin D status:

  • Many people spend little time in the sun with exposed skin (for example office work, clothing, sunscreen).
  • Through diet only around 2-4 µg of vitamin D are consumed per day, which is too little to achieve optimal levels without sun exposure.
  • In winter, 25(OH)D levels drop particularly sharply; a relevant share of the population falls below critical thresholds.

Targeted and well-thought-out supplementation can therefore be useful for many people - ideally embedded in a holistic health strategy.

From Sunlight to Capsule: How Vitamin D Works

How Vitamin D Works in the Body

Strictly speaking, vitamin D is a hormone precursor and influences far more than bone health. Scientifically approved health claims include:

  • Supporting normal immune function
  • Maintaining normal bones and teeth
  • Supporting normal muscle function
  • Contributing to the absorption and utilization of calcium and phosphorus

Vitamin D is therefore crucial for the metabolism, immune system and bone health.

How Vitamin D Is Produced

The body produces vitamin D itself. UV-B radiation from sunlight converts a precursor in the skin into vitamin D3 (cholecalciferol). Further conversion steps take place in the liver and kidneys.

In Germany, sunlight is sufficient for adequate vitamin D synthesis only from spring to early autumn; time spent outdoors, skin type and degree of coverage are key factors.

What Levels Are Optimal?

Vitamin D status is measured as 25-hydroxyvitamin D (25(OH)D).

The DGE and other expert bodies recommend:

  • Below 30 nmol/l (≈ 12 ng/ml): increased risk of deficiency and insufficient bone health
  • From 50 nmol/l (≈ 20 ng/ml): sufficient for bone health

The optimal range can vary individually. Interpretation of results should always be done by a physician.

Dosage, Safety, Regulation: Official Recommendations

Reference Values, NRV and Upper Limits

Several reference points are used when it comes to dosage:

  • D-A-CH reference value (DGE, ÖGE, SGE):
    • 20 µg of vitamin D per day (800 IU) for adults without relevant sun exposure
  • NRV (Nutrient Reference Value):
    • 5 µg/day (200 IU) as the European label value
  • EFSA upper limit (UL):
    • 100 µg/day (4,000 IU) for adolescents from 11 years and adults

The UL is not a target intake, but the safe upper limit for healthy individuals.

BfR: Caution With High Doses

The German Federal Institute for Risk Assessment (BfR) points out:

  • Even an additional daily intake of 100 µg (4,000 IU) can lead to undesirable effects such as reduced bone density, increased fall risk and heart problems.
  • For dietary supplements, the BfR recommends a maximum of 20 µg (800 IU) per day.
  • Very high long-term doses (for example 10,000-50,000 IU/day) can be harmful and should be avoided.

next d-complete: Safe, Tested Dosage

next d-complete contains D3, K2, magnesium and vitamin A - deliberately formulated within these recommendations.

One capsule contains 2,400 IU (60 µg) vitamin D3, 80 µg K2 (MK-7), 500 mg magnesium malate (of which 75 mg magnesium), and vitamin A. The recommendation is: 1 capsule every 3 days. This corresponds on average to 20 µg vitamin D3 daily (800 IU), exactly aligned with DGE and BfR guidelines.

next d-complete is therefore

  • within the recommended range (20 µg/day)
  • well below the EFSA upper limit (100 µg/day)

At a Glance: Reference Values and next d-complete

Metric Vitamin D value Assessment
NRV (label value) 5 µg/day (200 IU) Reference intake
D-A-CH reference value 20 µg/day (800 IU) According to DGE
BfR maximum (supplements) 20 µg/day (800 IU) Considered safe
EFSA upper limit (UL) 100 µg/day (4,000 IU) Maximum value
next d-complete (per capsule) 60 µg (2,400 IU) Single dose
next d-complete (1 capsule/3 days) 20 µg/day (800 IU) Within reference range

Why a Complex? Synergy of D3, K2, Magnesium & Vitamin A

Vitamin D3 - the Key Form

Dietary supplements almost always use vitamin D3 (cholecalciferol) - well researched and effective. next d-complete provides highly pure, laboratory-tested vitamin D3 "Made in Germany" in vegan capsules without unnecessary additives.

Vitamin K2 (MK-7) - for Bones & Blood Vessels?

Vitamin K activates proteins that incorporate calcium into the bones. For K2 (especially MK-7), there is evidence suggesting a positive influence on vascular health. However, the BfR emphasizes that protection against vascular calcification with high vitamin D intake is not clearly proven at present.

Practical note:

  • According to approved health claims, K2 contributes to the maintenance of normal bones.
  • If you take coumarin-type anticoagulants (certain blood thinners), you should only use vitamin K2 after consulting your doctor.

Magnesium - an Indispensable Cofactor

Magnesium acts as a cofactor in the activation of vitamin D and is required for enzymes such as 25-hydroxylase (liver) and 1α-hydroxylase (kidneys); a deficiency can reduce the effectiveness of vitamin D.

Established health claims include:

  • Reduction of tiredness and fatigue
  • Support of energy metabolism, muscle function, nervous system and bone structure

next d-complete therefore deliberately combines vitamin D3 with magnesium malate.

Vitamin A - as a Complement

Vitamin A influences the immune system and cell division. next d-complete provides retinyl palmitate in a moderate dose as part of the overall concept.

next d-complete: Quality, Concept, Use

next d-complete stands for:

  • Complex of D3, K2, magnesium, vitamin A
  • 120 vegan capsules, without unnecessary additives
  • Production "Made in Germany", laboratory-tested
  • Listed as a bestseller in the nextvital shop, with very high customer satisfaction (4.98/5 from over 40 reviews).

The dosage is designed so that you reach evidence-based reference values - an approach that reflects the recommendations of German expert committees.

Frequently Asked Questions

Here you will find 20 common questions about vitamin D, deficiency, dosage and how to use next d-complete.

1. What Is Vitamin D - Vitamin or Hormone?

Strictly speaking, vitamin D is a hormone precursor. Sunlight on the skin produces vitamin D3; the active hormone form is then generated through further processing in the liver and kidneys.

2. How Can I Tell If I Have a Deficiency?

A deficiency can only be reliably detected through a blood test (25(OH)D). Non-specific symptoms such as fatigue, muscle weakness and susceptibility to infections can have many different causes.

If you have symptoms or risk factors (little sun exposure, high degree of coverage, darker skin, older age), you should discuss a blood test with your doctor.

3. How Common Is Vitamin D Deficiency?

Large studies (DEGS1, KiGGS) show:

  • Many people fall below 30 nmol/l in winter.
  • Only just under half reach ≥ 50 nmol/l, the recommended level.

Vitamin D deficiency is widespread, particularly in people with low sun exposure.

4. Which Blood Values Are Considered Good or Critical?

Common threshold values (25(OH)D in serum):

  • < 30 nmol/l (≈ 12 ng/ml): increased risk of deficiency
  • 30-< 50 nmol/l: suboptimal status
  • ≥ 50 nmol/l (≈ 20 ng/ml): sufficient

Individual target ranges may vary depending on underlying conditions. Assessment should always be done by a physician.

5. How Much Vitamin D Is Recommended?

The DGE recommends 20 µg per day (800 IU) for adults without adequate sun exposure.

  • This is a guideline, not an individual treatment plan.
  • Personal requirements vary depending on baseline level, body weight and lifestyle.

6. Where Is the Safe Upper Limit?

The EFSA sets the UL at 100 µg/day (4,000 IU) from age 11 onwards. The BfR advises limiting vitamin D in dietary supplements to a maximum of 20 µg (800 IU) per day to keep total intake safely within limits.

Very high long-term doses (for example 10,000 IU/day) should be medically supervised to avoid complications.

7. What Is the Difference Between Vitamin D2 and D3?

D2 (ergocalciferol) comes from plant sources (such as UV-treated mushrooms), while D3 (cholecalciferol) comes from animal sources or the body's own synthesis.

Vitamin D3 usually raises 25(OH)D levels more efficiently and maintains them more stably. next d-complete therefore relies on D3.

8. Why Combine Vitamin D With K2?

Vitamin D increases calcium absorption; K2 activates proteins that help transport calcium into the bones. There is evidence suggesting potential benefits of K2 for bones and blood vessels.

The BfR notes:

  • The evidence base for K2 in combination with high vitamin D doses is still limited.
  • A reliable protective effect of K2 against vascular calcification has not been proven.

next d-complete contains K2 in a moderate dose tailored to typical needs.

9. What Role Does Magnesium Play in Vitamin D Metabolism?

Magnesium is required for the activation of vitamin D: it is needed for the hepatic and renal enzymes involved.

Studies show that magnesium deficiency can impair the effect of vitamin D.

next d-complete provides 500 mg magnesium malate per capsule (75 mg elemental magnesium), helping to support magnesium intake.

10. How Does next d-complete Differ From Single-Nutrient Products?

next d-complete combines:

  • Vitamin D3 (interval dosing)
  • Vitamin K2 (vegan MK-7)
  • Magnesium malate
  • Vitamin A (retinyl palmitate)

On top of that, there is the quality aspect: Made in Germany, laboratory-tested, vegan capsules, no unnecessary additives.

11. Who Is next d-complete Suitable For?

Suitable for:

  • People with little sun exposure (for example office workers, shift workers, people who wear covering clothing)
  • Individuals who want to support bone and muscle function
  • Users who value a tested vitamin D complex

For certain medical conditions or medications, you should consult a doctor before starting supplementation.

12. Dosage Recommendation for next d-complete

  • 1 capsule every 3 days with sufficient fluid.

This corresponds on average to 20 µg vitamin D3 daily (800 IU).

13. Why Take It Every Three Days?

Vitamin D is fat-soluble and stored in the body. A somewhat higher single dose every three days prevents large fluctuations while staying practical for everyday life: 60 µg spread over three days gives 20 µg/day.

14. Can I Also Take next d-complete Daily?

The recommendation is: every 3 days. A daily capsule would provide 60 µg (2,400 IU) per day - above the DGE and BfR guideline but below the EFSA upper limit.

Any dose adjustment outside the recommendation should only be made under medical supervision and ideally after checking blood levels.

15. What Should Be Considered With Medications?

  • Coumarin-type anticoagulants: Vitamin K2 can interact with these drugs; medical advice is essential.
  • Conditions such as hyperparathyroidism, kidney disease or a tendency to kidney stones require particular caution.

In general: If you take regular medications or have chronic illnesses, always clarify supplementation with your doctor.

16. How Long Should You Take Vitamin D?

If a deficiency is diagnosed by a physician, treatment usually starts with a short loading phase followed by a maintenance dose. Otherwise, maintenance aligned with reference values - as with next d-complete - is possible after medical consultation. Regular monitoring is advisable.

17. Is a Blood Test Necessary Before Taking Vitamin D?

The DGE does not consider routine measurements without suspicion strictly necessary.

A blood test is sensible if you have:

  • Clear symptoms or risk factors
  • Planned high-dose supplementation
  • Underlying medical conditions

For supplementation within the reference range (for example 20 µg/day), self-assessment is often sufficient, but a blood test can provide certainty.

18. What Do Users Experience With Vitamin D and next d-complete?

Individual reports are subjective but can provide clues about tolerability. In the nextvital shop, next d-complete is rated with very high satisfaction. Users particularly appreciate:

  • the combination of D3, K2, magnesium and vitamin A
  • the simple 3-day intake rhythm
  • trust in "Made in Germany" and laboratory-tested quality

Subjective effects such as "more energy" should always be viewed in the context of overall health.

19. Is Summer Sun Enough - and Why Supplement Anyway?

Regular time outdoors with uncovered skin can be sufficient in summer. In reality, however, everyday life often looks different: long hours indoors, clothing, sunscreen and our latitude all limit the body's own production.

A vitamin D complex like next d-complete provides a reliable, controlled supplement for times when sun exposure is low.

20. What Is the Role of Diet, Sun and Supplements?

Three pillars complement each other:

  • Sun: Expose your face, hands and arms to sunlight briefly several times a week without sunscreen - adjusted to your skin type and without getting sunburned.
  • Diet: Vitamin D-rich foods (fatty fish, eggs) contribute, but usually are not enough on their own.
  • Targeted supplementation: A tested product like next d-complete helps to safely close gaps.

In this way, you achieve a practical mix of the body's own synthesis, diet and controlled supplementation.

Conclusion: Three Concrete Steps for Your Vitamin D Routine

  1. Assess your individual risk:

    • How often are you outdoors with uncovered skin?
    • Do you have risk factors (age, skin color, weight, relevant health conditions)?

  2. Choose a strategy:

    • Combine moderate sun exposure, mindful nutrition and supplementation dosed in line with reference values.
    • A daily intake of around 20 µg vitamin D (800 IU) is considered safe and appropriate by DGE and BfR.

  3. Prioritize quality:

    • Use tested products manufactured in Germany with clearly declared ingredients.
    • next d-complete brings together D3, K2, magnesium and vitamin A in a laboratory-tested, practical format.

This article does not replace medical advice. If you are unsure - especially regarding dosage or pre-existing conditions - talk to your doctor or another qualified professional about your vitamin D status.