Signs of Vitamin D Deficiency: How to Recognise and What to Do

Vitamin D Deficiency: More Common Than You'd Think

Vitamin D deficiency is one of the most underdiagnosed nutritional problems in Europe. According to EFSA data, approximately 40% of Europeans have vitamin D levels below the recommended 50 nmol/L threshold. In Estonia and other Nordic countries, the prevalence rises even higher during winter months. The problem is that many deficiency symptoms are non-specific — they overlap with countless other health issues, causing vitamin D deficiency to be frequently overlooked.

Classic Signs of Vitamin D Deficiency

Physical Signs

Fatigue and low energy levels are among the most common complaints. One study found that people with vitamin D deficiency have a significantly higher rate of fatigue compared with those with adequate levels (Syed Zaman et al., 2010).

Muscle weakness and bone pain — vitamin D is essential for calcium absorption, which is critically needed for muscle and bone function. Deficiency often manifests as pain in the legs, lower back, and joints.

Frequent infections — vitamin D activates immune cells (T-lymphocytes, macrophages). Studies show that adequate vitamin D levels reduce the risk of respiratory infections by up to 40% (Martineau et al., 2017).

Slow wound healing — vitamin D promotes collagen production and immune cell activity at the wound site.

Mental and Neurological Signs

Mood disturbances, depression — vitamin D receptors are widely distributed in the brain. Low levels are associated with a higher risk of depression, particularly in winter (Anglin et al., 2013). Vitamin D deficiency is one contributing factor in seasonal affective disorder (SAD).

Concentration difficulties and brain fog — a vague but widely reported symptom in people with low vitamin D.

Sleep disturbances — vitamin D receptors are present in sleep centres of the brain; deficiency may contribute to poor sleep quality.

At-Risk Groups

Who is most vulnerable to vitamin D deficiency?

How to Diagnose Deficiency

The only reliable method is a blood test: 25-hydroxyvitamin D (25(OH)D). Your GP can order this test. Useful to know:

• The test is affordable (approximately €8–15 privately)
• Recommended timing: September (before starting supplements) and March (at the end of the winter period)
• Optimal range: 75–125 nmol/L

How to Correct It

Correcting deficiency depends on the severity of the initial level:

Mild deficiency (50–75 nmol/L):

• 2000–3000 IU D3 daily for 2–3 months
• Then recheck

Moderate deficiency (30–50 nmol/L):

• 4000 IU D3 daily for 3 months
• Combine with K2 for optimal effect

Severe deficiency (< 30 nmol/L):

• Usually requires medical guidance and potentially higher doses

MaxFit.ee offers effective correction options. OstroVit Vitamin D3 4000 IU 120 Caps is ideal for rapidly correcting winter deficiency. NOW Vitamin D3 5000 IU 120 softgels suits those with more significant deficiency. OstroVit Vitamin D3 4000 IU + K2 100 tabs adds K2 for better calcium direction into bones — particularly useful for those who have been deficient for a long time.

FAQ

Can you get enough vitamin D in summer if you go outdoors?

Yes in summer, but it depends on many factors: time of day (10:00–14:00 is best), exposed skin area, use of SPF protection, and seasonal variables. 20–30 minutes of active sunlight in summer can produce 10,000–25,000 IU of vitamin D, but this may not be enough to build reserves for winter.

Can you get enough vitamin D from food?

Hardly. The best food sources (fatty fish, cod liver oil) contain 200–400 IU per serving. Meeting the daily minimum (1500–2000 IU) from food alone is very difficult, especially given a typical Estonian diet.

Do vitamin D deficiency symptoms resolve quickly after starting supplements?

Most people feel improvement within 4–8 weeks, but this depends on the severity of the deficiency. Blood levels fully normalise within 2–3 months with adequate dosing.

References

1. Martineau, A. R., Jolliffe, D. A., Hooper, R. L., et al. (2017). Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis. BMJ, 356, i6583.
2. Anglin, R. E., Samaan, Z., Walter, S. D., & McDonald, S. D. (2013). Vitamin D deficiency and depression in adults: systematic review and meta-analysis. British Journal of Psychiatry, 202(2), 100–107.
3. Syed Zaman, S. H., et al. (2010). Vitamin D deficiency and chronic fatigue syndrome. Journal of Psychosomatic Research, 68, 35–41.
4. Cashman, K. D., Dowling, K. G., Skrabáková, Z., et al. (2016). Vitamin D deficiency in Europe: pandemic? American Journal of Clinical Nutrition, 103(4), 1033–1044.
5. Holick, M. F. (2007). Vitamin D deficiency. New England Journal of Medicine, 357(3), 266–281.