8 Signs of vitamin D deficiency you shouldn't ignore

8 Signs of vitamin D deficiency you shouldn't ignore

Written by Georgia Chappell & Reviewed by Paul Holmes

If you’ve got a vitamin D deficiency, you simply haven’t got enough vitamin D in your body. Without it, you can’t absorb essential vitamins needed to function properly. This can lead to fatigue and various bone and muscle issues. Learn how to spot the warning signs so you can stay fit and healthy all year round.

Understanding Vitamin D deficiency

What is Vitamin D deficiency?

A vitamin D deficiency is when your body doesn’t have enough vitamin D. That much is obvious. But what are the causes of vitamin D deficiency?

Vitamin D deficiency is a common condition, especially during the winter months, when there is less sunlight. That’s because a vitamin D deficiency is most commonly caused by a lack of exposure to sunlight. Why? Well, sunlight is what triggers the body to produce this essential vitamin – which in turn helps your body perform various important processes.

As well as exposure to sunlight, vitamin D can be gained through your diet. Dietary sources of vitamin D include fatty fish, fortified dairy products, and fortified cereals. However the UK government and the NHS recommend that everyone should take a vitamin D supplement to avoid vitamin D deficiency throughout Autumn and Winter.

What is Vitamin D good for?

Vitamin D is a crucial nutrient that plays several important roles in the body. Some of its key functions include:

1. Bone health: Vitamin D is essential for the regulation of calcium and phosphorus in the body, which are essential for maintaining healthy bones and teeth.1,2 It helps the body absorb calcium from the diet and promotes bone mineralisation.3

2. Immune system support: Vitamin D is known to play a role in the functioning of the immune system. It may help modulate the immune response and has been linked to a lower risk of certain infections.4

3. Muscle function: Vitamin D is involved in muscle function, and its deficiency has been associated with muscle weakness and pain.5

5. Mood and Mental Health: Some studies have explored the role that vitamin D might play in mood regulation, and its deficiency has been associated with conditions such as seasonal affective disorder (SAD).6

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Top 8 Signs of Vitamin D Deficiency

So, what are the most common symptoms of vitamin D deficiency? Explore the signs you’re not getting the vitamin D your body needs to work as it should, with a list of symptoms and conditions that can have a huge impact on your health.

1. Fatigue and tiredness

Vitamin D plays a role in energy production, and low levels may contribute to feelings of fatigue and general tiredness. One report from the Journal of the College of Physicians and Surgeons discusses a case where fatigue was a presentation of vitamin D deficiency, and symptoms improved with vitamin D supplementation.

Fatigue can have various causes, and vitamin D deficiency is just one potential factor. Other medical conditions, lifestyle factors, and overall health should always be considered, too.

Vitamin D for tiredness

2. Bone weakness and pain

Vitamin D is crucial for calcium absorption, and deficiency can lead to weakened bones and muscles. This study investigated the relationship between musculoskeletal pain and vitamin D deficiency in adults. It found that individuals with low vitamin D levels were more likely to experience musculoskeletal pain. This included experiencing bone pain particularly in the back and legs, and muscle weakness.

Maintaining adequate vitamin D levels through sunlight exposure, dietary sources, or supplementation when necessary is essential for overall bone health.

Vitamin D for bone weakness and pain

3. Mood changes and depression

Various studies have explored the link between vitamin D deficiency and mood disorders, including depression and anxiety. One particular trial investigated the impact of vitamin D supplementation on depressive symptoms in individuals with seasonal affective disorder.

Vitamin D for Mood changes and depression

4. Frequent Illness or Infections

Research has explored the potential role of vitamin D in immune function – suggesting an association between vitamin D levels and the risk of frequent illnesses or infections. Some meta-analysis undertaken examined individual participant data from various studies to assess the impact of vitamin D supplementation on preventing acute respiratory tract infections. The findings suggested a protective effect, particularly in individuals with lower baseline vitamin D levels.

While studies suggest a potential link between vitamin D levels and the risk of respiratory tract infections, it's essential to note that individual responses may vary. Vitamin D is proven to play a role in immune function, and maintaining adequate levels through sunlight exposure, diet, or supplementation is essential to overall health.

Vitamin D for illness and infection

5. Hair Loss

There is limited direct evidence establishing a clear link between hair loss and vitamin D deficiency. However, vitamin D is known to play a role in various physiological processes, including those related to skin and hair health.

For example, hair follicles have vitamin D receptors, with vitamin D involved in the regulation of hair follicle cycling. As a result, vitamin D deficiency might disrupt this process – contributing to hair loss alongside various other factors, including genetics, hormonal changes, and underlying health conditions.

Vitamin D for hairloss

6. Slow Wound Healing

Vitamin D is involved in the regulation of the immune system, and if you have a deficiency it could impair your body's ability to heal wounds. Vitamin D is essential for various physiological processes, including immune function and wound healing.

While there is a connection between vitamin D and wound healing, it's crucial to recognise that multiple factors contribute to the healing process, including overall health, nutrition, blood circulation, and the type and severity of the wound.

Vitamin D for wound healing

7. High Blood Pressure

There is some evidence suggesting a potential association between vitamin D levels and blood pressure regulation, but the relationship is complex, and more research is needed to establish causation. One systematic review explored the relationship between vitamin D levels and the risk of hypertension. The findings suggested an inverse association, indicating that individuals with higher vitamin D levels may have a lower risk of developing hypertension (low blood pressure).

Vitamin D for high blood pressure

Risk Factors and Prevention

Who is at risk of vitamin D deficiency?

Several factors can increase the risk of vitamin D deficiency. Anyone can develop a vitamin D deficiency, however there are some groups of people who are more likely to be at risk.

- Limited sun exposure

Individuals who have limited exposure to sunlight, either due to living in regions with minimal sunlight, spending most of their time indoors, or using excessive sun protection.

- Dark skin tone

People with darker skin produce less vitamin D when exposed to sunlight compared to those with lighter skin. This is because melanin, the pigment responsible for skin colour, reduces the skin's ability to produce vitamin D in response to sunlight.

- Older adults

Aging reduces the skin's ability to synthesise vitamin D. Additionally, older adults may spend more time indoors and could have a reduced efficiency in converting vitamin D into its active form.

- Obesity

Vitamin D is a fat-soluble vitamin, and individuals with obesity may have lower bioavailability of vitamin D because it can be separated in fat tissues.

- Breastfed infants

Breast milk is not a rich source of vitamin D. Infants exclusively breastfed without vitamin D supplementation may be at risk of deficiency.

- Limited dietary intake

Individuals with a diet low in vitamin D-rich foods, such as fatty fish, eggs, and fortified dairy products, may be at risk.

- Geographic location

People living at higher latitudes, where sunlight is less intense, especially during the winter months, might also have reduced opportunities for vitamin D synthesis.

How does vitamin D deficiency impact the immune system?

Vitamin D plays a crucial role in supporting the immune system, and its deficiency can have various impacts on immune function. Here are some ways that vitamin D deficiency can affect your immune system.

Reduced antimicrobial peptide production: Vitamin D is involved in the regulation of antimicrobial peptides, which are essential for the innate immune system's ability to defend against pathogens. Deficiency may lead to decreased production of these peptides.

Impaired phagocytosis: Vitamin D helps enhance the ability of immune cells, such as macrophages, to eliminate pathogens through a process called phagocytosis. Insufficient vitamin D levels can impair this function.

Altered T-cell function: Vitamin D is involved in the modulation of T-cell function, a critical component of the adaptive immune response. Deficiency may impact the balance of T-cell subsets – potentially affecting the body's ability to mount an effective immune response.

Suppressed immune response: Vitamin D deficiency has been associated with a suppressed innate immune response – affecting the body's ability to recognise and respond to pathogens quickly.

Impaired respiratory immune defence: Vitamin D deficiency has been linked to respiratory infections. Adequate vitamin D levels are thought to play a role in maintaining the integrity of the respiratory epithelium and supporting immune defences in the respiratory tract.

Longer recovery time: Vitamin D deficiency may prolong the recovery time from infections, as the immune system may not function optimally in the absence of sufficient vitamin D.

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5 ways to prevent vitamin D deficiency

Preventing vitamin D deficiency involves a combination of sunlight exposure, dietary choices, and, if necessary, supplementation. Here are five ways to help prevent vitamin D deficiency.

1. Get sunlight exposure: Vitamin D is often referred to as the "sunshine vitamin" because the skin produces it in response to sunlight. Spending time outdoors, especially during the morning or late afternoon, can help your body produce vitamin D. Aim for about 10–30 minutes of sunlight exposure to the face, arms, legs, or back at least twice a week.

2. Eat vitamin D-rich foods: Include foods rich in vitamin D in your diet. Good dietary sources include fatty fish (e.g. salmon, mackerel, and sardines), cod liver oil, egg yolks, and fortified foods such as fortified milk, orange juice, and cereals. Incorporating these foods into your meals can contribute to maintaining adequate vitamin D levels.

3. Take vitamin D supplements: If you have limited sun exposure, are in a high-risk group, or have difficulty obtaining enough vitamin D from food sources, consider vitamin D supplements. However, it's important to consult with your doctor before starting any supplementation to determine the appropriate dosage for your specific needs.

4. Maintain a healthy weight: Vitamin D is fat-soluble, so individuals with obesity may have lower bioavailability of vitamin D because it can become separated in fat tissues. Maintaining a healthy weight through a balanced diet and regular exercise can contribute to optimal vitamin D levels.

5. Get regular health check-ups: Schedule regular health check-ups with your doctor. Blood tests, specifically measuring 25-hydroxyvitamin D levels, can help tell if you’re at risk of deficiency. Based on the results, a GP can recommend appropriate interventions.

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Diagnosis and treatment

How is vitamin D deficiency diagnosed?

Vitamin D deficiency is diagnosed through a blood test that measures the concentration of 25-hydroxyvitamin D, which is the major circulating form of vitamin D. This test reflects both dietary intake and the synthesis of vitamin D in the skin in response to sunlight.

The results of this blood test determine the individual's vitamin D status. The measurements are typically reported in nanograms per millilitre (ng/mL) or nanomoles per litre (nmol/L).

The general classifications are:

· Normal: 20-50 ng/mL (or 50-125 nmol/L)

· Insufficient: 12-20 ng/mL (or 30-50 nmol/L)

· Deficient: Below 12 ng/mL (or 30 nmol/L) 

In some cases, additional tests might be ordered to assess specific aspects of vitamin D metabolism, or to identify underlying health conditions contributing to the deficiency.

Diagnosis and treatment for vitamin D

How do you recover from vitamin D deficiency?

Recovering from vitamin D deficiency involves addressing the underlying cause and implementing strategies to increase vitamin D levels. Here are steps you can take to recover from vitamin D deficiency:

Consult with a doctor

If you suspect vitamin D deficiency, speak with your GP. They can assess your specific situation, review your medical history, and provide personalised guidance.


If your vitamin D levels are significantly low, your doctor may recommend vitamin D supplements. The dosage will depend on the severity of the deficiency. Common forms of vitamin D supplements include vitamin D2 and vitamin D3.

Sun exposure

Increase your exposure to sunlight in a safe manner. Spend time outdoors, especially during the morning or late afternoon when the sun is less intense.

Dietary changes

Include vitamin D-rich foods in your diet. Incorporating foods such as fatty fish and cod liver oil into your meals can contribute to maintaining adequate vitamin D levels.

Regular monitoring

Follow up with your doctor for regular monitoring of your vitamin D levels. This may involve additional blood tests to assess your progress.

Address underlying causes

If your vitamin D deficiency is related to an underlying health condition, such as malabsorption disorders, kidney problems, or certain medications, work with your doctor to address these issues.

What are the best dietary sources of Vitamin D?

Vitamin D is found in various foods, and some of the best dietary sources include:

Vitamin D is found in various foods, and some of the best dietary sources include:

Fatty Fish

 Fatty fish are among the richest sources of vitamin D. This includes:

- Salmon
- Mackerel
- Sardines
- Herring
- Tuna

Cod Liver Oil

Cod liver oil is a potent source of vitamin D. However, it should be eaten in moderation due to its high vitamin A content.

Egg Yolks

Egg yolks contain vitamin D, but the concentration may vary. Look for eggs labelled as "enriched" or "high in vitamin D" for higher levels.

Fortified Plant-Based Milk Alternatives

Some plant-based milk alternatives, such as soy milk, almond milk, and oat milk, are fortified with vitamin D.

What are the best dietary sources of vitamin D?

Fortified Cereals and Breakfast

Foods Some cereals and breakfast foods, including oatmeal, are fortified with vitamin D. Check the product labels for information on fortification.


When you can’t get enough vitamin D in your diet, supplementation is a quick and easy way to get the vitamin D you need. Choose our popular vitamin D3 capsules, or try the effective combination of vitamin D and K for an additional boost.

Vitamin D deficiency FAQS

Recapping vitamin D deficiency

Vitamin D deficiency results from a combination of factors, and both adults and children can be affected. Essential things to remember when it comes to vitamin D deficiency include:

- Spending limited time outdoors, especially during peak sunlight hours, or consistently using sun protection measures can reduce the skin's ability to produce vitamin D.

- A diet lacking in vitamin D-rich foods, such as fatty fish, egg yolks, and fortified dairy products can cause vitamin D deficiency – especially during the darker months when your exposure to sunlight is heavily reduced. Consider taking vitamin D supplements to help with this.

- Disorders affecting the absorption of fat may lead to reduced absorption of fat-soluble vitamins, including vitamin D. Conditions include celiac disease and Crohn's disease.

If you think yourself or one of your children are suffering from a vitamin D deficiency, it’s important to always speak with a doctor first to discuss the best solution for you.

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