Vitamin D3 4000 I.U.

All the sunshine vitamin you need and more
With just 1 capsule a day

High-dose formula
30-day supply

High-powered vitamin D3 supplement that’s exactly what everyone needs these days

Most people don’t know that there’s a global problem concerning vitamin D3 - what is more, most people have no idea it’s their problem too! Up to 75% of the world population has low vitamin D3 levels. Since this is one of the key vitamins for immunity, you can see why it’s so important to keep your levels up these days.

Vitamin D plays many crucial roles in your body – starting with immune system support

Also called the sunshine vitamin, vitamin D is produced in your body with the help of sunlight. It is an essential vitamin that performs many vital life functions, which is why sufficient vitamin D levels are crucial for good health.

Contributes to normal immune system function

Helps maintain normal muscle function

Contributes to maintenance of normal bones and teeth

Contributes to normal absorption and utilisation of calcium and phosphorus

Supports normal cell division

Sources of vitamin D

1. Sunlight

Yes, your body can produce vitamin D when exposed to sunlight – but does it? You need about 15 minutes of midday sun (between 10 a.m. and 3 p.m.), with your forearms, face and lower legs uncovered, several times a week, to keep your levels where you need them.

Sitting next to a sunny window indoors doesn’t count, since UVB rays (which are crucial for vitamin D production) can’t get through the glass. In the fall, winter and early spring, sunlight doesn’t contain enough UVB radiation, which is why your skin can’t produce vitamin D.

2. Food

Some vitamin D is found in oily fish, egg yolks, some dairy, liver and mushrooms. But while it’s important to include vitamin D sources into your diet, it’s very difficult to get the recommended amount from food alone. In fact, some studies suggest we only get between 10 and 20% of vitamin D that way.

3. Supplements

D3 supplements are an efficient way of covering your daily vitamin D needs, especially in times like these, when your immune system needs all the support it can get.

Our ALL IN A DAY Vitamin D3 delivers a high-potency formula with 4000 IU (100 μg) of vitamin D3! Current research suggests consuming up to 4000 IU of vitamin D per day should be ideal for optimal blood levels in most people.

Vitamin D deficiency – a global health challenge

Vitamin D deficiency is a major health problem which affects people of all ethnicities and age groups worldwide – even those that live in countries close to the equator, where it was previously assumed that UV radiation was sufficient to prevent this from happening. Estimates suggest that over 1 billion people worldwide are vitamin D deficient or insufficient.1,2

Prevalence of low vitamin D status in adults worldwide.1

This is the result of several different issues, starting with scarce exposure to sunlight due to the modern way of life. In fact, studies suggest we spend over 90% of our time indoors, which is far from ideal for vitamin D production.

The symptoms are generally so subtle and common that we often fail to realise they’re connected to vitamin D deficiency. As a result, they’re often ignored – even in cases where they seriously affect our lives. The most common symptoms include:

1. Getting ill often

Studies show that vitamin D deficiencies lead to compromised immunity and increased risk of infections, especially the flu and respiratory infections.3

2. Bone loss, pain and achy joints

Without vitamin D, your body has difficulties absorbing calcium from food, which is why it “sucks” calcium from bones instead, leading to weaker bones, increased risk of fractures and osteoporosis.

3. Back pain

Studies suggest back pain, especially lower back pain, is a common sign of vitamin D deficiency.

4. Tiredness and fatigue

Excessive fatigue is a common sign of vitamin D deficiency, since low vitamin D levels negatively affect your energy levels.

5. Muscle weakness and pain

Along with muscle cramps, these have both been linked to low vitamin D levels.

6. Mood changes

Vitamin D is important to healthy brain function, and insufficient levels have been linked to low mood and a greater risk of depression

Groups that benefit from D3 supplementation the most

Due to the modern way of life, we spend most of our days in stuffy offices, production halls or at home – missing the window for efficient vitamin D production. And during our summer holidays, when we do hang outside around midday more often – we wear sunscreen, which interferes with it as well. As a result, most of us are likely to have low vitamin D levels and could greatly benefit from supplementation.

Groups that could use it the most are the following.

Are you at risk of vitamin D deficiency?
Take the test & find out

To make things easier, we’ve developed a quick test that should help you establish whether you’re at risk of having low vitamin D levels. Ready to find out?


Vitamin D3 4000 I.U.

Get the sunshine vitamin that’s crucial for the immune system during the season of flus and colds.

High-potency formula with 4000 IU (100 μg) of vitamin D3 in easy-to-swallow capsules with no artificial colouring. 30-day supply!

  • High-potency, high-dose formula with 4000 IU (100 μg of vitamin D3)
  • Small, easy-to-swallow capsules
  • No artificial colourings
  • 30-day supply
  • Produced with 15 years of expertise in supplement development and production
  • 1.7 million of Sensilab customers worldwide
  • The vitamin D content is verified by the independent laboratory ChemProf

30-Day Money-back Guarantee!

Use the product for up to 30 days and see the results first-hand. If for any reason you are not completely satisfied, simply return the empty package and get a full refund.

Quality. Safety. Expertise.

We have over 1.7 million happy customers worldwide and are present in over 40 countries across Europe. Thus, it’s our mission and responsibility to design and manufacture products using the highest-quality, effective, clinically tested and natural active ingredients. We follow the highest pharmaceutical GMP and HACCP standards at our state-of-the-art production facilities.



When developing our products, we analyse the latest findings, studies and trends in the fields of nutrition, supplements and biochemistry.


Our own production facilities

EU-based modern pharmaceutical plant where we follow GMP and HACCP standards


Certified raw materials

From reliable and traceable suppliers who must show certificates proving the quality and integrity or the materials


Lab analyses

Our products are tested twice – as raw materials and finished products, so each product comes with purity and microbiological integrity guarantees.


Verified vitamin D content

The vitamin D content is verified by the independent laboratory ChemProf.


Due to the modern way of life, low vitamin D levels are highly prevalent around the world. The main source of vitamin D is the sun, which means you need to spend enough time in sunlight to keep them where you need them. This usually means about 15 minutes a day, with your face, forearms and lower legs uncovered. But not just whenever you have the time.

There’s actually a very specific time frame. The UVB rays, which are crucial for vitamin D production, are only strong enough between 10 a.m. and 3 p.m. But where do you usually find yourself around that time? Most likely, in a stuffy office, production hall or at home. Sadly, sitting next to a sunny window indoors won’t do the trick, since the UVB rays can’t get through the glass – you have to be outdoors for that!

And there’s more. Staying in the shade and wearing sunscreen interferes with vitamin D synthesis, too – an SPF 30 reduces vitamin D production by more than 95%. Smog and air pollution play an important part in that too.

That’s why supplementation is recommended throughout the year, and is especially important from October to April. Take the test above to find out if you belong to a group of people who are at higher risk of vitamin D deficiency.

Not many foods are good sources of natural vitamin D. Some vitamin D is found in oily fish (such as salmon, herring, sardines and mackerel), egg yolks, some dairy, liver and mushrooms. While foods of animal origin contain it in the form of vitamin D3 (cholecalciferol), plant-based sources have it in the form of vitamin D2 (ergocalciferol) which appears to be less effective at increasing vitamin D blood levels.

Vitamin D is a fat-soluble vitamin that gets stored in the body’s adipose (fat) tissue. Vitamin D toxicity is extremely rare but can develop over time if extreme doses are taken daily. Current research suggests consuming up to 4000 IU of vitamin D per day should be ideal for optimal blood levels in most people. Yet doses of up to 10000 IU have not been shown to result in toxicity in healthy people either.4,5

ALL IN A DAY Vitamin D3 contains 4000 international units of vitamin D3, which corresponds to 100 μg of vitamin D3. Current research suggests consuming up to 4000 IU of vitamin D per day should be ideal for optimal blood levels in most people.

Just take 1 capsule a day, with a glass of water after a meal – and that’s it, you’re all set.

Sources and further reading

  1. A systematic review of vitamin D status in populations worldwide:  
  2. Is vitamin D deficiency a major global public health problem?: 
  3. Vitamin D and the Immune System: 
  4. The 2011 report on dietary reference intakes for calcium and vitamin D from the Institute of Medicine: what clinicians need to know: 
  5. Risk assessment for vitamin D: 
  6. Immune-boosting role of vitamins D, C, E, zinc, selenium and omega-3 fatty acids: Could they help against COVID-19?: 
  7. Vitamin D Supplementation:  
  8. Can vitamin D help with symptoms of COVID-19?: