Vitamin D deficiency

Last updated: 25 August 2026
Reviewed by: Specialist doctors from the Elfcare quality team

Feeling low on energy, catching colds more often, or noticing muscle aches? These subtle signs might point to something deeper, like low vitamin D. While the symptoms are subtle, vitamin D is essential for bone strength, immune function, and mood regulation.

In northern climates like Sweden, where sunlight is limited for much of the year, this deficiency is more common in certain groups, particularly people with darker skin, older adults, and those with limited sun exposure, and it can be easily overlooked. A simple blood test is the only way to identify it definitively, and correction is typically straightforward.

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What is vitamin D deficiency?

Vitamin D is a fat-soluble hormone produced through sunlight and found in foods like fatty fish and eggs. Its role goes far beyond bone health; it is a master regulator that strengthens the immune system, supports muscle function, and influences brain chemistry.

A clinical deficiency is defined as a level below 50 nmol/L, while insufficiency falls between 50–75 nmol/L. Low levels hinder calcium absorption, often leading to persistent fatigue, bone pain, and weakened immunity. These states are common in northern climates but are easily corrected once identified.

Symptoms of vitamin D deficiency

Vitamin D deficiency symptoms are non-specific and develop gradually, which is why they are so frequently attributed to other causes or simply dismissed. Common signs include:

  • Fatigue or low energy

  • Muscle weakness or cramps

  • Bone or joint pain, particularly in the back, hips, and legs

  • Frequent colds or infections

  • Mood changes like low mood or irritability

  • Hair thinning or loss

  • Slow wound healing

  • Cognitive difficulties such as reduced concentration or mental clarity

In severe or prolonged deficiency, symptoms can progress to osteomalacia (softening of the bones) in adults, or rickets in children, both characterised by significant bone pain and structural changes.

What causes vitamin D deficiency?

Vitamin D deficiency is driven by a combination of limited sunlight exposure, inadequate dietary intake, and impaired absorption, all of which are exacerbated by northern geography and modern indoor lifestyles.

Common contributing factors include:

  • Limited sun exposure, especially in winter or for those with indoor lifestyles

  • Darker skin tone, which reduces vitamin D production

  • Ageing, as older adults produce less vitamin D naturally

  • Diet low in vitamin D, especially in plant-based diets

  • Certain medications like steroids or anticonvulsants

  • Digestive conditions that affect absorption, such as celiac or Crohn’s disease

How is vitamin D deficiency detected?

Vitamin D deficiency is straightforward to diagnose. A single blood test provides a definitive answer. Our panel assesses the following markers to provide a complete picture of your bone metabolism:

  • 25-OH Vitamin D: The primary marker used to confirm deficiency, insufficiency, or adequacy.

  • Corrected calcium: Measures absorption levels; low calcium is a direct consequence of severe deficiency.

  • Phosphate: Regulated by Vitamin D; low levels contribute to the softening of bone tissue.

  • Magnesium: Essential for Vitamin D activation; a deficiency here can make supplementation less effective.

  • ALP (alkaline phosphatase): An enzyme that rises when bone turnover increases due to poor mineralisation.

  • CRP: A marker of systemic inflammation, which Vitamin D helps modulate and regulate.

Why early detection matters

Vitamin D deficiency often develops silently, and you may feel fine for months before symptoms like chronic fatigue, muscle aches, or low mood become part of daily life. Left unaddressed, sustained deficiency is associated with a wider range of consequences: accelerated bone density loss and fracture risk, higher susceptibility to respiratory infections and autoimmune conditions, increased cardiovascular risk, links to depression and cognitive decline, greater muscle weakness and fall risk in older adults, and a higher risk of insulin resistance and type 2 diabetes.

Catching a deficiency early means it can usually be corrected simply, through nutrition, safe sun exposure, or supplementation, well before it contributes to any of these longer-term consequences.

How Elfcare can help

Elfcare's blood panel measures 25(OH)D directly and definitively. No imaging is needed, no specialist referral is required for initial assessment, and results are immediately actionable.

Our panel also includes calcium, phosphate, magnesium, and ALP, giving a complete picture of vitamin D's downstream effects on bone and mineral metabolism, not just the deficiency marker itself.

If our blood tests identify vitamin D deficiency or related metabolic imbalance, we take care of further diagnostics or refer you to the appropriate specialist.

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Summary

Vitamin D deficiency is a silent but common condition that impacts your energy, mood, and immunity. Because it affects everything from bone density to heart health, early detection via a blood test is the most effective way to prevent long-term complications.

A comprehensive blood panel measures 25(OH)D alongside calcium, phosphate, and magnesium to provide a full map of your metabolic health. Identifying these levels allows you to take simple, proactive steps to restore vitality before symptoms arise. If a deficiency is found, we provide the necessary guidance or specialist referrals to get you back on track.

Early awareness is the simplest way to protect your physical and mental performance.

Last updated: 25 August 2026
Reviewed by: Specialist doctors from the quality team at Elfcare

FAQ

  • Vitamin D deficiency occurs when circulating levels of 25-hydroxyvitamin D fall below 50 nmol/L — the threshold below which the body cannot adequately regulate calcium absorption, immune function, muscle performance, and bone mineralisation. It is common worldwide and particularly prevalent in northern countries with limited annual sunlight.

  • Persistent fatigue, muscle weakness or aching, bone and joint pain, frequent infections, low mood, and cognitive difficulties are the most common signs. Symptoms are non-specific and develop gradually, which is why deficiency is so frequently missed without a blood test.

  • The primary cause is insufficient sun exposure, particularly relevant in Sweden and other northern countries. Contributing factors include darker skin tone, age, obesity, malabsorption conditions (coeliac, Crohn's), certain medications, and limited dietary intake. Many people have multiple overlapping risk factors.

  • A blood test measuring 25-hydroxyvitamin D (25(OH)D) is the definitive diagnostic tool. Results are interpreted alongside calcium, phosphate, magnesium, and ALP to give a complete picture of vitamin D status and its downstream metabolic effects.

  • Yes. Elfcare's blood panel includes 25(OH)D as a standard marker, providing a direct, definitive measurement of vitamin D status. Supporting markers including calcium, phosphate, magnesium, and ALP are also included. If deficiency is identified, we take care of further diagnostics or refer you to the appropriate specialist.

  • Yes, and correction is straightforward. Supplementation with vitamin D3, combined where needed with magnesium and calcium, restores levels effectively in most people. Sun exposure and dietary adjustments support long-term maintenance. In severe deficiency, higher-dose supplementation under medical supervision may be recommended. Symptoms typically improve within weeks to months of achieving adequate levels.