Vitamin D deficiency

What is vitamin D deficiency?

Vitamin D deficiency means you don’t have enough vitamin D for your body to maintain health.

Vitamin D is an essential vitamin that helps the body absorb calcium and phosphorus, which are essential for healthy bones and teeth.

It also supports muscle, immune, and nervous system function.

Why do we need vitamin D?

Low levels can weaken your bones and increase the risk of osteoporosis and bone fractures. In children, it can cause rickets, where soft, weak bones may become deformed.

Vitamin D may also play a role in:

• Protecting against certain cancers (such as bladder, brain, bowel, and skin cancers).

• Reducing the risk of falls.

• Helping to stave off depression and low mood.

• Keeping energy levels normal.

The main source of vitamin D is sunlight; you can also get it from foods - particularly fortified ones - and vitamin D supplements.

Symptoms of vitamin D deficiency

Symptoms of vitamin D deficiency differ in adults and children.

In adults

You might feel:

• Generally tired, achy, and unwell.

• Have pain and muscle weakness - making it hard to climb stairs, stand up from the floor or a low chair, or can cause a waddling walk.

• Your bones may feel tender when pressed, especially over the ribs or shins, and bone pain can occur in the lower back, hips, pelvis, thighs, and feet.

• Fatigue and low energy, even with adequate sleep.

• Frequent illnesses or infections, due to reduced immune function.

• Osteomalacia (softening of bones), which can lead to bone pain and fractures.

• Increased risk of fractures, particularly in older adults.

• Low mood or depression.

• Brain fog or difficulty concentrating.

• Sleep disturbances.

• Hair thinning or hair loss (may be associated in some cases).

• Slow wound healing.

• Bone loss (osteoporosis) with long-term deficiency.

Some people with vitamin D deficiency might not have any symptoms at all, or they can be very subtle.

In children

They might have:

• Soft or weak bones, especially in the skull and legs. Legs may appear bowed. This is known as rickets.

• Bone pain (often in the legs) and muscle pain or weakness.

• Slow growth, with height affected more than weight. Some children may be slow to start walking.

• Delayed teething because the milk teeth develop more slowly.

• Increased irritability.

• More frequent infections. In severe cases, weak chest muscles and soft ribs can cause breathing problems.

• Very severe deficiency can cause low calcium levels, leading to muscle cramps, seizures, or breathing difficulties - this needs urgent medical care.

• Rarely, very low levels can weaken the heart muscle (cardiomyopathy).

In babies, severe vitamin D deficiency can develop muscle cramps, seizures, and breathing difficulties, all caused by very low calcium levels due to the lack of vitamin D.

Causes of vitamin D deficiency

A vitamin D deficiency may happen if:

• You have an increased need for it (but are unable to take in enough in your diet)- such as growing children, pregnant women, and breastfeeding women

• Your body is unable to make enough of it - due to a lack of sunlight on the skin, ageing, having darker skin, certain gut, liver or kidney diseases, or some medicines (such as barbiturates or anti-HIV drugs).

• You do not have enough vitamin D in your diet - particularly if you follow a strict vegetarian, vegan, or a non-fish-eating diet.

Who is at risk of vitamin D deficiency?

Vitamin D deficiency is common and affects about 1 in 5 adults and children in the UK.

Those at risk of deficiency include people who are:

• Pregnant or breastfeeding.

• Aged 1-4 years.

• Over 65 (older adults are less efficient at producing vitamin D).

• Have little exposure to sunlight, because they:

  • Are housebound.

  • Are confined indoors for long periods.

  • Cover their skin for cultural reasons.

• Have darker skin, for example people of African, African-Caribbean or South Asian origin.

• Have particular gut (bowel), kidney or liver disease

How much vitamin D do I need a day?

It is recommended that everyone in the UK over 1 year old take 10 micrograms (400 International Units) a day from October to March.

Those who are at higher risk of low vitamin D are advised to take a vitamin D supplement of 10 micrograms (400 International Units) a day all year round.

Babies from birth to 1 year old should have a supplement in the form of vitamin D drops of 8.5 to 10 micrograms a day.

Babies having 500 ml or more of formula milk per day do not need supplements, as formula milk already has vitamin D added.

How is vitamin D deficiency diagnosed?

Vitamin D deficiency is diagnosed with a simple blood test to determine your vitamin D levels.

Blood tests for calcium and phosphate levels and liver function may also show changes linked to a low level of vitamin D.

Sometimes a wrist X-ray is requested by a paediatrician (specialist) for a child in order to see how the bones are developing. This can assess how severe the problem is by looking for changes in the wrist bones.

Treatment of vitamin D deficiency

The main treatment for vitamin D deficiency is to take vitamin D supplements (D2/D3). This is a form of vitamin D called ergocalciferol(D2) or calciferol(D3).

Vitamin D3 is available from:

• Sunlight: UVB rays trigger vitamin D3 production in the skin.

• Animal-based foods:

  • Fatty fish (salmon, mackerel, sardines, tuna).

  • Cod liver oil.

  • Egg yolks.

  • Liver.

• Fortified foods:

  • Milk and dairy products.

  • Some plant milks (soy, almond, oat).

  • Breakfast cereals.

  • Some yogurts and juices.

Vitamin D2 is available from:

• Plants and fungi:

  • UV-exposed mushrooms (fresh or dried).

• Fortified foods:

  • Some plant-based milks.

  • Breakfast cereals.

Additionally they are available as:

• High-dose supplements (tablets or liquids) - these are available in different strengths and may be taken either daily, weekly or monthly. They are usually given to growing children or people who have very low levels.

• Standard dose supplements (tablets or liquids) - these are taken daily for about 12 months to gradually restore vitamin D levels and are mainly used for prevention.

• Vitamin D injection - in some cases a single small injection of vitamin D will be given that can last up to six months. Injections are only used when oral supplements haven't worked due to increased risks of side effects and vitamin D toxicity.

After deficiency is corrected, long-term maintenance therapy is often needed at a lower dose to prevent vitamin D levels from falling again.

Are there any risks to taking vitamin D supplements?

There are some risks involved with taking vitamin D supplements, these are:

• Taking too much can cause vitamin D toxicity, leading to high calcium levels. High calcium levels are potentially dangerous.

• It can interact with certain medicines (such as digoxin or some diuretics), so high doses may need to be avoided.

• It may cause problems in people with certain medical conditions (such as kidney, liver, or hormonal disorders), where specialist advice may be needed.

How to prevent vitamin D deficiency

You can help prevent a vitamin D deficiency by:

Increased sunlight exposure

During the UK summer months (April-September) daily sunlight exposure can help your body produce enough vitamin D.

• For people with fair skin - 10-15 minutes of direct sunlight on the face and forearms around the middle of the day, 2-3 times a week.

• For people with darker skin - The exact time needed varies by location, season, and skin tone, but people with darker skin generally need longer exposure than those with lighter skin.

The sunlight has to fall directly on to bare skin, you cannot get enough vitamin D from sunlight through a window.

Always wear sunscreen to protect your skin from sunburn. Sunscreen does not block the absorption of vitamin D.

Eating vitamin D-rich foods

Vitamin D can also be obtained from foods that either contain it naturally or have it added to them.

Foods high in vitamin D include:

• Oily fish - such as sardines, pilchards, herring, trout, tuna, salmon, mackerel, and kippers.

• Egg yolk, red meat and liver.

• Cod liver oil (although this should be avoided if you're pregnant).

• Fortified foods (vitamin D added to them) - such as infant formula milk, most margarines, and some cereals.

In some countries (but not in the UK) all milk is fortified with vitamin D.

Frequently asked questions

How long does it take to correct a vitamin D deficiency?

It usually takes a few weeks to several months to correct vitamin D deficiency, depending on how low your levels are, the dosage of supplements, and how consistently you take them.

Can I take vitamin D all year round?

Yes, vitamin D supplements are generally safe to take all year round, especially if you don’t get enough from sunlight or diet. Always follow official guidelines or your doctor’s advice to avoid taking too much.

Does a lack of vitamin D cause depression?

A lack of vitamin D has been linked to low mood and depression, however, not everyone with a deficiency develops depression. Maintaining healthy levels through sunlight, diet, or supplements may help support mental wellbeing.

Where can I buy vitamin D supplements?

Vitamin D dietary supplements can be bought at pharmacies, supermarkets and online retailers. High doses however can only be obtained by a prescription from a doctor.