Vitamin D is sometimes called the “sunshine vitamin,” yet a large proportion of people, especially in the UK, do not get enough of it, particularly through the darker months. Because symptoms build up slowly, many people live with vitamin D deficiency for years without realising it is behind their fatigue, aching bones, or low mood. This guide covers the key symptoms, who is most at risk, and how to correct a deficiency safely.
What Is Vitamin D Deficiency?
Vitamin D deficiency happens when the body does not have enough vitamin D to properly absorb calcium and phosphorus, the two minerals responsible for keeping bones and teeth strong. Vitamin D also plays a role in immune function, muscle strength, and mood regulation, which is why a shortfall can affect far more than just your bones.
Common Symptoms of Vitamin D Deficiency
Physical Symptoms
- Fatigue and low energy, even with a full night’s sleep
- Bone and joint pain, particularly in the lower back, hips, and legs
- Muscle weakness or aches, sometimes making stairs or standing up feel harder than usual
- Frequent colds or infections, linked to reduced immune function
- Slow wound healing
Mood and Mental Symptoms
- Low mood, which can overlap with seasonal affective symptoms in winter
- Brain fog or difficulty concentrating
- Sleep disturbances, including trouble staying asleep
Who Is Most at Risk?
Certain groups are considerably more likely to develop a deficiency:
- People who spend most of their time indoors
- Those with darker skin, since more melanin reduces the skin’s ability to produce vitamin D from sunlight
- Older adults, whose skin produces vitamin D less efficiently
- People who cover most of their skin for cultural, religious, or medical reasons
- Anyone following a strict vegan diet, since most natural dietary sources are animal-based
- People living in the UK and other northern countries, where winter sunlight is too weak for the skin to produce vitamin D
If low mood or poor sleep is one of your symptoms, it is worth reading our guide on how to sleep better naturally, since sleep and vitamin D levels are closely connected.
Why Does the UK Have Widespread Vitamin D Deficiency?
Between October and March, UK sunlight is too weak in UVB rays for the skin to produce meaningful amounts of vitamin D, regardless of how much time is spent outdoors. This is why public health guidance recommends everyone over the age of one consider a daily supplement during the autumn and winter months, not just people already showing symptoms.
How Is Vitamin D Deficiency Diagnosed?
A simple blood test, known as the 25-hydroxyvitamin D test, is the only reliable way to confirm vitamin D deficiency. Levels below 25 nmol/L are generally classed as deficient, while levels between 25 and 50 nmol/L may be considered insufficient. Many people with low vitamin D have no obvious symptoms at all, so testing is the only way to be certain.
Best Food Sources of Vitamin D
Since few foods naturally contain vitamin D, diet alone is rarely enough, but these sources can help:
- Oily fish, such as salmon, mackerel, and sardines
- Egg yolks
- Fortified foods, including some cereals, dairy products, and plant milks
- Mushrooms exposed to UV light
Vitamin D Supplements: How Much Do You Need?
UK guidance recommends a daily supplement of 10 micrograms (400 IU) from October to March for most adults and children over one year old, with some at-risk groups advised to take it year-round. Taking significantly more than recommended without medical advice is not safer and can, in rare cases, lead to toxicity, so it is worth sticking to standard doses unless a doctor advises otherwise.
Safe Sun Exposure
Around 10 to 15 minutes of midday sun on the arms and face, a few times a week between April and September, is generally enough for most people in the UK to produce adequate vitamin D. This should always be balanced against skin cancer risk, so exposure should be brief and without burning.
When to See a Doctor
Speak to a GP if you have ongoing bone or muscle pain, persistent fatigue that does not improve with rest, frequent infections, or if you fall into one of the higher-risk groups listed above. A blood test can confirm whether vitamin D is the cause and guide the right dose of supplementation.
FAQ
What are the early warning signs of vitamin D deficiency?
Early signs typically include fatigue, low mood, and mild bone or muscle aches, though many people have no noticeable symptoms at all.
Can low vitamin D cause hair loss?
Some research links low vitamin D to hair thinning, though it is usually one of several contributing factors rather than a sole cause.
How long does it take to correct a vitamin D deficiency?
With consistent supplementation, blood levels typically improve within 8 to 12 weeks, though symptom improvement can vary from person to person.
Do I need a vitamin D supplement even if I feel fine?
In the UK, public health guidance recommends a daily supplement from October to March for most people, regardless of symptoms, because winter sunlight is not strong enough to produce vitamin D naturally.
Final Thoughts
Vitamin D deficiency symptoms are often mistaken for everyday tiredness, which is exactly why so many cases go undiagnosed. If you recognise several of the signs above, particularly during the winter months, a simple blood test and a standard daily supplement are usually enough to bring levels back to a healthy range.
