Vitamin D Deficiency: Symptoms You Can Easily Miss

You stand in front of the mirror and see a person who, despite 8 hours of sleep, feels constantly tired. Everything hurts - your back, legs, sometimes for no reason. Colds chase you one after another. You blame your diet, stress, the weather. But the real cause could be much simpler - and smaller - than you think.

It's vitamin D. Or rather, the lack of it.

The sunshine vitamin which, as it turns out, is essential not only for strong bones but for the proper functioning of nearly every cell in your body. And the average European? Doesn't get enough. Studies show that up to 80-90% of the population in Northern Europe has a deficiency or insufficient levels of vitamin D, especially during the autumn and winter months.

What exactly is vitamin D and why is it so important?

Let's start from the beginning. Vitamin D isn't actually a vitamin - it's a steroid hormone. Your body can produce it on its own - under the influence of UVB rays from the sun hitting your skin. The problem? In Northern Europe from October to March, the sun sits too low for this process to occur at all.

What does vitamin D do in the body?

• Regulates calcium and phosphorus absorption - without it, bones demineralise and become brittle
• Supports the immune system - helps fight bacterial and viral infections
• Affects mood and brain function - vitamin D receptors are in the brain; its deficiency is linked to depression
• Regulates blood pressure - protects the heart and blood vessels
• Supports muscle strength - deficiency leads to weakness and muscle pain
• Modulates the immune system - reduces the risk of autoimmune diseases

In other words - it's everywhere your body needs it. And when it's lacking? Problems start appearing.

10 symptoms of vitamin D deficiency that are easy to miss

Here are the signals your body sends when it has too little sunshine vitamin. The problem is they're general enough that they're easily blamed on stress, tiredness or an approaching flu.

1. Chronic fatigue and lack of energy

Sleep 8 hours but feel like you haven't slept at all in the morning? Dragging through the whole day? This could be a vitamin D deficiency.

Studies show that people with low vitamin D levels (below 20 ng/ml) report significantly more fatigue than those with normal levels. What's more, supplementation often brings rapid improvement, especially in women.

2. Frequent infections and colds

Do you fall ill more than three times a year? Does every cold drag on for weeks? Vitamin D is one of the key players in the immune system.

It works in several ways:

• Activates immune cells (T and B lymphocytes, macrophages)
• Increases production of antimicrobial peptides (e.g. cathelicidin)
• Modulates the inflammatory response - doesn't let the immune system "overdo it"

Practical advice: If you catch every virus going round the office or your child's nursery, get your vitamin D levels tested. It's a simple and affordable test.

3. Muscle and joint pain

Your back, legs, arms hurt - but you don't know why? You haven't exercised hard, haven't been moving furniture. It just hurts.

Vitamin D deficiency often manifests as diffuse musculoskeletal pain. Vitamin D receptors are found in muscle cells - when it's lacking, muscles are weaker and more susceptible to pain.

Interesting fact: In people with chronic pain where no other cause was found, vitamin D deficiency was identified in up to 70% of cases.

4. Low mood, melancholy, depression

Autumn and winter are times when there's little sun. And times when many people feel worse mentally. That's no coincidence.

Vitamin D affects the production of serotonin - the neurotransmitter responsible for good mood. The less vitamin D, the less serotonin. The result? Greater susceptibility to depression, especially seasonal (SAD - Seasonal Affective Disorder).

Studies show that vitamin D supplementation in people with a deficiency improves mood and reduces depressive symptoms.

5. Weakness and reduced muscle strength

Feel weaker than you used to? Finding it harder to get up from a chair, climb stairs, lift a shopping bag?

Vitamin D plays a crucial role in muscle function. Its deficiency leads to atrophy of type II muscle fibres (responsible for fast, powerful contractions) and increases the risk of falls - especially in older adults.

6. Slow-healing wounds

A cut, graze, minor injury - and it takes weeks to heal? Vitamin D is essential in the tissue regeneration process.

It participates in creating new blood vessels, affects collagen production and has anti-inflammatory properties. Without it, the healing process is slowed down.

7. Hair loss

Is your hair falling out more than usual? Vitamin D deficiency is linked to hair loss - especially alopecia areata.

Vitamin D receptors are found in hair follicles. Its deficiency disrupts the hair growth cycle and can lead to shedding.

8. Problems falling asleep and sleep quality

Tossing and turning in bed for hours? Waking up at night and can't fall back asleep? Low vitamin D levels could be one of the reasons.

Studies show a link between vitamin D deficiency and sleep disorders - difficulty falling asleep, frequent awakenings and poorer sleep quality.

9. Pale skin

This is logical - if you have fair skin and avoid the sun, you produce less vitamin D. But it works the other way too: dark skin makes vitamin D production harder (melanin acts as a UVB filter).

People with dark skin living in Northern Europe are in a particularly high-risk group for deficiency.

10. Excessive head sweating

This is a lesser-known but classic symptom - especially in infants. Excessive head sweating, particularly during feeding or sleeping, can indicate a vitamin D deficiency.

In adults it's a rarer symptom, but if it occurs without another cause - it's worth checking your vitamin D levels.

Who is in the highest risk group?

Vitamin D deficiency can affect anyone, but some people are particularly vulnerable:

• Older adults (65+) - skin produces less vitamin D with age, and older people spend less time in the sun
• People with dark skin - melanin makes vitamin D production harder
• Overweight and obese people - vitamin D "accumulates" in fat tissue and is less available to the body
• People working indoors - lack of sun exposure
• People with absorption disorders - Crohn's disease, coeliac disease, cystic fibrosis
• People after bariatric surgery - reduced intestinal absorption
• Pregnant and breastfeeding women - increased demand
• People taking certain medications - e.g. corticosteroids, anti-epileptic drugs
• People with kidney or liver disease - impaired vitamin D activation

If you belong to any of these groups - check your vitamin D levels. It could change how you feel.

How to test vitamin D levels?

It's simple. All you need is a blood test - 25(OH)D (25-hydroxyvitamin D). This is the most reliable marker of vitamin D levels in the body.

How to interpret the results?

• Below 20 ng/ml (50 nmol/l) - deficiency
• 20-30 ng/ml (50-75 nmol/l) - insufficient level
• 30-50 ng/ml (75-125 nmol/l) - normal level
• 50-100 ng/ml (125-250 nmol/l) - optimal level (according to some experts)
• Above 100 ng/ml (250 nmol/l) - possible overdose

When to test? Best at the end of winter (February-March) - that's when vitamin D levels are lowest. But if you have symptoms - you can test at any time.

Cost: In private laboratories €15-30. No referral needed.

Where to get vitamin D? Sun, diet, supplements

1. Sun - naturally, but...

Your body can produce as much as 10,000-20,000 IU of vitamin D after full-body sun exposure for 20-30 minutes (at the peak of summer, around midday).

The problem?

• In Northern Europe from October to March, the sun can't produce vitamin D (UVB too weak)
• SPF sunscreens block production (which is needed to protect against skin cancer)
• People work indoors - there's no time for sun

Conclusion? Sun is a great source in summer, but insufficient in winter.

2. Diet - as a supplement

Vitamin D in food occurs in small amounts. The best sources are:

• Oily sea fish (salmon, herring, mackerel) - 400-1000 IU per 100 g
• Egg yolks - about 40 IU per egg
• Liver - about 50 IU per 100 g
• Fortified milk, yoghurt, breakfast cereals - 40-100 IU per serving
• Mushrooms (e.g. UV-exposed button mushrooms) - up to 400 IU per 100 g

The problem? To cover the daily requirement (2000 IU), you'd need to eat 200 g of salmon or 50 eggs every day. That's unrealistic.

3. Supplementation - the most reliable method

In Northern European climate conditions, vitamin D supplementation isn't a fad - it's a necessity, especially from October to April.

How much to supplement?

• Adults (prevention): 1000-2000 IU daily year-round
• People in risk groups: 2000-4000 IU daily
• With a confirmed deficiency: 4000-10,000 IU daily for 8-12 weeks, then check levels and reduce the dose
• Children: according to paediatrician's recommendations (usually 400-1000 IU)

Important: These are general recommendations. If you have a blood test showing a deficiency - talk to your doctor about an individual dose.

Which form of vitamin D is best?

You'll find various forms on the market. Here's what's worth knowing:

D2 vs D3 - which to choose?

• Vitamin D2 (ergocalciferol) - plant-derived, absorbs less well and works for a shorter time
• Vitamin D3 (cholecalciferol) - the same form that skin produces under sunlight, better absorbed

Choose D3. It's more effective and better at raising blood vitamin D levels.

In what form?

• Oil drops - easy to dose, absorb well (vitamin D is fat-soluble)
• Soft gel capsules - convenient, stable dosage
• Tablets - cheapest, but absorb more slowly (especially without fat)
• Spray - rapid absorption through the oral mucosa

Practical advice: Best to take vitamin D with a meal containing fat (e.g. eggs, nuts, avocado, olive oil). This increases absorption by up to 50%.

Vitamin D with K2?

Preparations combining vitamin D3 with vitamin K2 are increasingly recommended. Why?

Vitamin D increases calcium absorption. Vitamin K2 directs that calcium to the bones (where it's needed), rather than to blood vessels (where it can lead to calcification).

Do you have to? No. But if you supplement high doses of vitamin D (above 4000 IU) for a prolonged period, it's worth considering a preparation with K2.

Can you overdose on vitamin D?

Yes, but it's difficult. Vitamin D accumulates in the body (it's fat-soluble), so theoretically it can be overdosed.

When could there be a problem?

• Long-term intake of very high doses (above 10,000 IU daily for months)
• Blood level exceeding 150 ng/ml

Overdose symptoms:

• Nausea, vomiting
• Weakness, fatigue
• Excessive thirst, frequent urination
• Hypercalcaemia (too much calcium in the blood) - can lead to kidney stones, vascular calcification

Conclusion: Doses up to 4000 IU daily are considered safe for most adults. At higher doses, it's worth monitoring blood levels every few months.

How long to supplement and when to check levels?

It depends on your starting level:

• Deficiency (below 20 ng/ml): Intensive supplementation (4000-10,000 IU) for 8-12 weeks, then check levels and adjust the dose
• Insufficient level (20-30 ng/ml): 2000-4000 IU daily for 2-3 months, then check
• Normal level: 1000-2000 IU daily as prevention year-round (especially autumn-winter)

When to check? After 8-12 weeks of supplementation, then once every 6-12 months (or sooner if symptoms don't subside).

Should everyone supplement vitamin D?

In Northern Europe? Almost everyone. Experts agree - in our climate, vitamin D should be supplemented year-round, especially in autumn and winter.

Exceptions:

• People with hypercalcaemia (excess calcium in blood)
• People with hypercalciuria (excess calcium in urine)
• People with sarcoidosis or other granulomatous diseases
• People with calcium kidney stones (after medical consultation)

If you don't belong to any of these groups - vitamin D supplementation is simply a sensible investment in your health.

Where to buy and how much does it cost?

Vitamin D supplements are available without a prescription in pharmacies, drugstores, health food shops and online.

Prices vary significantly:

• Basic preparations (2000 IU, 60 capsules): €3-8
• Premium preparations (with K2, in oil): €8-20
• Drops for infants: €4-10

It's worth comparing prices! The same product in different pharmacies can differ in price by as much as 30-40%. Check CheaperForDrug before buying - over a year, you can save a good amount on supplementation for the whole family.

Frequently asked questions (and honest answers)

Does vitamin D really help immunity?

Yes. Studies show that people with normal vitamin D levels fall ill less frequently with upper respiratory infections. The effect is particularly noticeable in people who had a deficiency - supplementation reduces the risk of infection by as much as 30-50%.

What time of day should I take vitamin D?

It doesn't matter much - the most important thing is to take it with a meal containing fat. Many people take it in the morning with breakfast (easier to remember), but evening is fine too.

Can vitamin D help with depression?

In people with a deficiency - yes. Supplementation can improve mood and reduce depressive symptoms. But it won't replace psychiatric treatment if you have clinical depression. It's support, not a panacea.

Can you take vitamin D during pregnancy?

Yes, you even should. Vitamin D deficiency in pregnancy increases the risk of complications (gestational diabetes, premature birth, low birth weight). Recommended dose: 1500-2000 IU daily (after consulting your gynaecologist).

Why do I still feel unwell after supplementation?

There could be several reasons:

• The dose is too low - check your blood levels
• You have another health problem (e.g. hypothyroidism, anaemia)
• You need time - improvement may come after 4-8 weeks

If after 3 months of supplementation you don't feel a difference - see a doctor. There could be something else going on.

Summary - what to remember?

Vitamin D deficiency is a common problem in Northern Europe - up to 90% of the population has insufficient levels, especially in winter.

Symptoms are subtle: fatigue, frequent infections, muscle aches, low mood - easy to miss or blame on stress.

Check your levels - the 25(OH)D test costs €15-30 and gives you certainty. Optimal level is 30-50 ng/ml.

Supplement D3 - in Northern European climates, it's a necessity, not a fad. Preventive dose: 1000-2000 IU daily, more for deficiency (after consultation).

Take it with fat - increases absorption by up to 50%.

Compare prices - vitamin D preparations vary significantly in price. Check CheaperForDrug before buying.

Disclaimer

This information is for educational purposes and does not constitute medical advice. If you have symptoms of vitamin D deficiency or plan to take high doses, consult a doctor. Every body is different and may require an individual approach.

Vitamin D is a small thing, but it has enormous significance. If you feel constantly tired, keep falling ill, everything aches - check your levels. It could be exactly what your body has been lacking.

Look after your health wisely - and affordably. With CheaperForDrug you'll find the best prices on vitamin D supplements and save on your whole family's health.