Vitamin D deficiency: why it is so common here

From mid-autumn to mid-spring the sun in Bulgaria does not sit high enough for skin to produce vitamin D. However long you spend outdoors.

Deficiencies  ·  4 min read  ·  Updated 2026-10-06

Vitamin D is made in the skin under ultraviolet B light. That light only reaches the ground when the sun is above a certain angle. At Bulgaria's latitude, around forty-two degrees, that angle is not reached from roughly October to roughly April.

That means something concrete. In winter, time outdoors produces no vitamin D at all, regardless of how long you stay out. The body lives on what it stored over the summer and on what you take in through food or a supplement.

Who is most at risk

• People who work indoors through all the daylight hours
• Adults over sixty-five, because skin synthesises less with age
• People with darker skin, because melanin acts as a natural filter
• People carrying excess weight, because the vitamin is fat soluble and distributes into fat tissue
• People who cover more of the body for religious or personal reasons
• Infants and young children, which is why supplementation is a standard recommendation for them

The symptoms that get missed

The trouble with vitamin D deficiency is that it does not hurt. It shows up as things easily blamed on tiredness, age or the weather.

• Fatigue that does not improve with rest
• Muscle weakness, especially in the thighs, noticed when standing up from a chair or climbing stairs
• Dull bone ache, most often in the lower back, pelvis and calves
• Lower mood through the winter months
• More frequent upper respiratory infections
• Slower healing

None of this is specific. Which is exactly why it is checked with a test, not by how you feel.

How it is tested properly

The marker is 25(OH)D, that is 25-hydroxy vitamin D. It is the storage form and it reflects your reserves. There is also a 1,25(OH)2D test, but it is not suitable for assessing reserves and leads to wrong conclusions.

The test needs no fasting and can be done at any time of day. The most informative moment is the end of winter, somewhere between February and March, when values are at their lowest for the year.

How to read the result

Values are given in nanograms per millilitre or in nanomoles per litre. The generally accepted reading is as follows. Below twenty nanograms per millilitre counts as deficiency. Between twenty and thirty is insufficiency. Above thirty counts as sufficient. Above one hundred is the zone where toxicity becomes a risk.

Labs in Bulgaria give both units. If yours reports nanomoles, divide by two and a half to reach nanograms.

How to supplement sensibly

The dose depends on your starting value, your weight and the reason for the deficiency, so a regimen is set by a doctor, especially where values are low. A few things hold true regardless.

• Take it with food containing fat. The vitamin is fat soluble. A tablet on an empty stomach is absorbed considerably less well.
• Vitamin K2 is worth it at higher doses. It directs calcium to bone rather than to blood vessels. That is why the D3 with K2 combination is so widespread.
• Magnesium is part of the conversion. With a marked magnesium deficiency, vitamin D works less well.
• Do not push megadoses on your own initiative. Vitamin D accumulates. Overdose raises blood calcium, which is a real problem, not a theoretical one.
• Retest after three months. That shows whether the dose is doing its job, instead of guessing.

Food is not enough

Oily fish is the best source. A hundred grams of salmon or mackerel delivers a meaningful amount. Egg yolk and liver contribute too. But to cover the daily requirement from food alone you would need oily fish nearly every day, which almost nobody does.

So through the winter months at our latitude a supplement is sensible for most people, not an exception.

NLS, Vega and EAV are wellness methods for orientation, not medical diagnostics. This article is educational and is not medical advice. It does not replace examination, testing or consultation with a doctor. Do not stop or change prescribed treatment without your doctor.