Taking vitamin D is an excellent preventative and therapeutic measure. Whether it’s an increased susceptibility to infections, autoimmune diseases, degenerative disorders, or problems like diabetes, high blood pressure, depression, and dementia, a vitamin D deficiency is usually a causal factor. We explain how to determine a vitamin D deficiency with a home test, how much vitamin D you need, and how to properly combine vitamin D with calcium, magnesium, and vitamin K.

Why Vitamin D matters?

Vitamin D plays a key role in maintaining healthy bones by supporting calcium absorption and preventing bone loss. But its benefits go far beyond that.

This powerful nutrient is also known for its anti-inflammatory effects, making it essential in the management of chronic conditions that involve inflammation—such as heart disease, autoimmune disorders, and even mood-related conditions like depression.

Low vitamin D levels have been associated with:

• Frequent infections
• Fatigue and low mood
• Poor wound healing
• Increased risk of osteoporosis and fractures
• Diabetes and high blood pressure

It’s no surprise that so many people feel better once their vitamin D levels are restored.

Vitamin D Deficiency Is Common – Here’s Why

Vitamin D is not a true vitamin. True vitamins must be ingested through food. However, the body can obtain vitamin D from sunlight alone, as the vitamin is produced in the skin under the influence of UVB radiation.

To produce enough vitamin D from sun exposure, you need to spend regular time outdoors with uncovered skin, without high-SPF sunscreen, and typically in spring/summer in temperate regions.

For most people – especially those working indoors or living in areas with low sunlight in winter – that simply doesn’t happen. As a result, vitamin D deficiency is widespread.

Even in Australia, where the sun is strong, many people experience low vitamin D due to sunscreen use, protective clothing, and indoor living.

What Makes Vitamin D Unique?

The bone vitamin is one of the fat-soluble vitamins, along with vitamins A, E , and K. This means two things:

1. For the absorption of vitamin D from the intestine, some fat is always required (see below under “Correct intake: Always with a little fat”).
2. The vitamin can be stored in the body (in fatty tissue and liver), which is almost never the case with water-soluble vitamins (B, C).

The advantage is that once your stores are full, you don’t have to take vitamin D every day. Your body can rely on a full supply for weeks or even months.

The disadvantage is that it’s possible to overdose on fat-soluble vitamins, which is something you need to be careful about when taking them. While excess water-soluble vitamins are usually simply excreted in the urine, this is not the case with fat-soluble vitamins. Therefore, cases of vitamin A overdose are occasionally reported, for example, in regions where fish liver is popular. This contains particularly high levels of vitamin A.

Can You Overdose on Vitamin D?

As far as vitamin D is concerned, the risk of an overdose usually only arises if very high doses are taken in the form of dietary supplements over a longer period of time.

50 µg or 2,000 IU per day is considered the recommended maximum dose in Europe and North America. However, clinical studies show that even long-term intake of 10,000 IU daily poses no risks. An overdose could occur at 50,000 IU per day and serum levels above 150 ng/ml. Hypercalcemia (too much calcium in the blood) can then develop, according to an analysis by Indian researchers published in the Oman Medical Journal in May 2011 (1).

Symptoms of vitamin D overdose include:

• Extreme thirst, frequent urination
• Nausea, vomiting, or constipation
• Muscle weakness and fatigue
• Confusion or irregular heartbeat

Ideally, blood levels of vitamin D should be below 150 ng/ml, as even indigenous peoples rarely reach higher levels, despite spending their daily time in the sun without clothing. Levels above 300 ng/ml clearly indicate the beginning of the toxic range.

Overdose from food or sun?

Since vitamin D is rarely found in food, it is almost impossible to overdose (unless you eat a lot of fish liver).

It’s also almost impossible to overdose from sun exposure. Apparently, the body has protective mechanisms that stop vitamin D production through the skin once a sufficiently high serum level is reached.

On a sunny summer day, the body rarely absorbs more than 10,000 IU of vitamin D – and this only happens if you spend the entire day in the sun almost unclothed (swimming trunks/bikini).

Only in cases of extreme sun exposure (years of spending all day on the beach in hot regions) could adverse consequences of a vitamin D overdose occur, but even then only if there is a vitamin K2 deficiency and possibly an overly well-intentioned calcium intake.

It is therefore more likely that taking too high a dose of the vitamin in the form of a dietary supplement could lead to problems.

Vitamin D supplement from mushrooms and sun

Since the actual vitamin D content of mushrooms is unknown, the appropriately prepared edible mushrooms can be regularly incorporated into the diet, so that in the long term you only need to take low-dose supplements or, at some point, perhaps even no supplements at all.

The correct intake

Below, we describe all the factors you need to know to properly take vitamin D. First, we’ll discuss the four vital substances the vitamin needs to work properly, then how to measure your vitamin D levels, and finally, we’ll present two methods you can use to determine or calculate the right dose for you.

1. Take vitamin K2

Vitamin D enhances calcium absorption—but without vitamin K2, that calcium may end up in your arteries instead of your bones. Vitamin K2 directs calcium to where it’s needed: your teeth and bones.

We recommend:

• 100 µg of vitamin K2 (MK-7) for up to 2,500 IU of vitamin D daily
• 200 µg of K2 if taking more than 2,500 IU/day

If you’re on blood thinners or medications that interact with vitamin K, speak with your healthcare provider first.

2. Support with Vitamin A

Vitamin D and vitamin A are synergistic. A 2020 study found that vitamin D is more effective when vitamin A intake is adequate. Aim for 1 mg of vitamin A per day, preferably from food sources like liver, eggs, or orange veggies.

3. Don’t Forget Magnesium

Magnesium supports over 300 enzymatic processes in the body—including how vitamin D is converted into its active form. Without enough magnesium, your vitamin D levels might not rise effectively.

Good magnesium sources include leafy greens, nuts, seeds, and whole grains. You can also supplement if needed, ideally with a well-absorbed form like magnesium glycinate or citrate.

4. Vitamin D and calcium only advisable in certain situations

Vitamin D is considered THE bone vitamin par excellence, and it’s often believed that proper intake also includes calcium. However, this only seems to be useful in certain cases, namely:

1. if, for example, the risk of osteoporosis is to be reduced during menopause
2. if osteoporosis is already present and the risk of bone fractures should be reduced
3. if a low-calcium diet is practiced that provides significantly less than the daily recommended 1,000 mg of calcium

However, those who consume sufficient calcium should not take additional calcium when taking vitamin D (especially at very high doses). This could increase the risk of hypercalcemia.

Correct intake: Measure your vitamin D levels beforehand!

Correct intake of vitamin D can only take place if you know your actual value and can then calculate the appropriate dose for you or have it advised by your doctor.

Therefore, have your vitamin D levels measured first. Otherwise, you could be taking far too little and therefore not feeling any effect. Or you could be taking far more than necessary, which would place unnecessary strain on your body.

Your family doctor or alternative practitioner can perform the measurement. You can also perform a vitamin D home test yourself. However, you should also discuss the results with a doctor or alternative practitioner to be on the safe side.

If you order the test kit online, it costs approximately $55. You prick your finger (the necessary accessories are included in the test), add a few drops of blood to the sample tube, seal it, and send it to the lab in the enclosed mailing bag. You’ll receive the results by mail within 5 to 7 business days.

Correct intake: Which dose? – Method 1

You can then determine the dose you need (have it approved by your doctor/alternative practitioner) and obtain the appropriate preparation.

Proper vitamin D intake also includes having your levels re-measured after two to three months. First, to see how your levels have increased and second, to adjust your dose to the new level.

Correct intake: Which dose? – Method 2

The goal should be a blood level of at least 30 ng/ml, preferably around 40 to 50 ng/ml (100–125 nmol/l) of vitamin D3 (25(OH)-vitamin D3). The appropriate dose for you is calculated based on your current level and your desired level, taking your body weight into account.

In cases of severe deficiency, the procedure described in the article linked above may not lead to healthy vitamin D levels quickly enough. Therefore, we present the method developed by Dr. Raimund von Helden, author of the highly recommended book “Healthy in Seven Days – Success with Vitamin D Therapy.”

Dr. von Helden divides the intake of vitamin D into two parts of therapy: initial therapy and long-term or maintenance therapy.

1. Initial therapy after a deficiency is aimed at replenishing vitamin D stores, which should occur as quickly as possible so that the deficiency symptoms that usually occur can be resolved as quickly as possible. A single dose is administered. This is followed by a transition to the dose of maintenance therapy.
2. Continuous therapy provides the amount of vitamin D required to compensate for daily losses and maintain healthy vitamin D levels over the long term.

Calculating the dose for initial therapy

To raise vitamin D levels by 1 ng/ml (3.74 nmol/l), 10,000 IU are needed for a body weight of 70 kilograms. For a different body weight, calculate the value proportionally. Do not exceed 7,000 IU per kilogram of body weight.

For example, if you weigh 70 kg, have a current value of 15 ng/ml (52 nmol/l), and want to achieve a value of 35 ng/ml (121 nmol/l), then choose a single dose of 200,000 IU as your initial therapy. If you weigh only 60 kg, then take about 170,000 IU.

The initial dose is very high. We recommend discussing this method of administration with your doctor or alternative practitioner beforehand.

Calculating the dose for long-term therapy

Assuming a body weight of 70 kilograms, 3,333 IU of vitamin D per day or 23,000 IU per week are required. Here, too, the dose is calculated proportionally for a different body weight.

Those who spend a lot of time in the sun during the summer can take a break from vitamin D supplements. However, levels probably wouldn’t develop to a worryingly high level if they continued taking the supplement despite sunbathing.

Correct intake: Always with a little fat

If you take vitamin D supplements that come as powder in capsules with black coffee, water, or juice, this will result in absorption of the vitamin, but absorption will be rather low. As a fat-soluble vitamin, vitamin D should always be taken with some fat.

Too much fat isn’t a good idea either. So, if you take the vitamin supplement with a thick bread and butter or fatty cheese, you won’t be able to absorb the ideal dose. Too much fat seems to inhibit absorption.

A 2013 study showed that taking vitamin D with 11 grams of fat resulted in 16 percent higher absorption than taking it with 35 grams of fat and 20 percent higher absorption than taking it with 0 grams of fat.

It makes no difference whether you consume a fat made from polyunsaturated fatty acids (hemp oil, linseed oil, sunflower oil), one from monounsaturated fatty acids (olive oil, avocados, almonds) or one from saturated fatty acids (coconut oil).

Correct intake: Through the skin

If you cannot tolerate vitamin D supplements or if your vitamin D levels simply do not increase despite taking vitamin D supplements correctly, you can also apply the vitamin to your skin, as it can also be absorbed through the skin.

To do this, choose a liquid preparation without any unfavorable additives, such as vitamin D3 drops, which consist only of vitamin D3 and MCT fats (medium-chain fats from, for example, coconut oil).

But here, too, you only dose according to your own needs and apply the drops, for example, to your forearm, where the skin is most receptive.

Keep educated

There’s a certain empowerment that comes with understanding how your body works. When you give it what it needs – sunlight, movement, nourishment, and the right micronutrients – it responds with energy, resilience, and vitality.

Vitamin D is just one piece of that beautiful puzzle. And with the right knowledge, you’re in the best position to support your health naturally, wisely, and with confidence.