Vitamin D deficiency symptoms: what to look for

Vitamin D deficiency means your body does not have enough vitamin D to keep your bones, muscles, immune system and mood working properly. In the UK it is defined as a blood level of 25-hydroxyvitamin D below 25 nmol/L, while 25 to 50 nmol/L counts as insufficient and 50 nmol/L or above is considered adequate for most people.

The tricky part is that low vitamin D often creeps up on you. Many people feel tired, achy or run down and put it down to a busy life, getting older, or the British weather, when a simple blood test would tell a different story. NICE estimates that somewhere between 8% and 24% of UK adults have low vitamin D status, and the figure climbs in winter.

Below you will find the common signs, the weird and easily missed ones, and the specific questions people ask us most, from fatigue and hair loss to dizziness and weight gain. Pain gets its own section, because low vitamin D is one of the most overlooked causes of ongoing bone, muscle and joint aches. If you want to jump straight to raising your levels, our Vitamin D3 4000 IU is a simple daily option, but read on first so you know what you are actually dealing with.

The most common signs of vitamin D deficiency

If you are searching for the signs of vitamin D deficiency, these are the ones doctors see most often in adults. You do not need to have all of them. Even one or two that stick around for weeks is a good reason to check your levels.

Bone and muscle symptoms are the classic giveaway because vitamin D controls how well you absorb calcium. When levels drop, your body pulls calcium from your bones to keep blood levels stable, which softens the bones over time. In adults this is called osteomalacia, and in children it causes rickets. If your symptoms centre on your bones and joints, our Joints and Bones collection covers the wider nutrient picture too.

Weird symptoms of vitamin D deficiency

Not every sign of low vitamin D is obvious. Because vitamin D receptors sit in tissues all over the body, from your nerves to your skin to your inner ear, a deficiency can show up in ways that feel random or unrelated. These are the weird symptoms of vitamin D deficiency that people rarely connect to a nutrient at all.

• Unbearable itchiness or burning sensations on the skin, without a rash. This particularly tends to affect the lower legs at first, but can eventually affect the whole body. As the deficiency worsens, it intensifies from annoying itching to constant stinging pain. 
• Forgetfulness and brain fog, which other people will notice more than you do. It tends to be more severe and bizarre than commonplace absent-mindedness. If your spouse or colleagues are commenting on it, it's likely worse than you think and should not be ignored. 
• A profound feeling of illness. You may not be able to put your finger on it, but you will feel ill inside and know that something is badly wrong. 

• Excessive daytime sleepiness, where you nap after work or fade badly in the afternoons despite sleeping normally at night.

• Bone tenderness, where it genuinely hurts to press on your shins or breastbone rather than a vague ache.

• Hair thinning or patchy hair loss, which is linked to vitamin D's role in the hair follicle cycle.

• Dizziness or a spinning sensation when you move your head, connected to balance organs in the inner ear.

• Mood swings that can be mistaken for perimenopause, a thyroid problem or simple stress.

• Getting ill far more often than the people around you, a sign your immune defences are running low.

Remember that you should never attempt to self-diagnose and treat. If you suspect your may have a vitamin D deficiency, see your GP for a professional evaluation. 

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Can vitamin D deficiency cause fatigue?

Yes. Fatigue is one of the most common and most under-recognised symptoms of vitamin D deficiency. Vitamin D helps your cells produce energy, so when levels fall, tiredness can set in even when your sleep is fine.

In one published case, a 61-year-old man with worsening daytime sleepiness, to the point of napping daily and struggling at work, was found to be vitamin D deficient with no other cause. His fatigue improved once his levels were corrected. Larger reviews back this up, suggesting vitamin D supplementation can reduce the severity of fatigue specifically in people who are deficient to begin with.

Fatigue rarely travels alone with vitamin D. It often comes bundled with low mood and aching muscles, which is why the whole picture matters. If your energy is the main issue, you may also find our Energy and Stamina range useful alongside getting your levels checked.

Vitamin D deficiency and pain: bone, muscle and joint

Pain is one of the clearest reasons to take low vitamin D seriously, and it is the symptom that first earned vitamin D its reputation as a natural pain reliever. If you have unexplained back pain, muscle pain or joint pain that will not settle, your vitamin D level is worth checking.

How common is deficiency in people with chronic pain?

Very common. In a study of Swiss rheumatology patients, 86% were found to have a vitamin D deficiency, and a quarter had a severe deficiency below 25 nmol/L. Their levels were lower than patients with osteoporosis, and the very lowest were found in people with inflammatory arthritis and fibromyalgia.

Why does low vitamin D make pain worse?

Vitamin D reduces inflammation by lowering cytokine and prostaglandin levels, which are the main chemical messengers of pain. Research suggests it specifically inhibits Prostaglandin E2, which may explain its pain-relieving effect. People with very low levels, below 30 nmol/L, tend to feel the most benefit from correcting a deficiency, while those already above 50 nmol/L notice far less.

Does topping up vitamin D actually reduce pain?

The evidence points that way for people who are deficient. In a meta-analysis of 19 randomised controlled trials involving 3,436 participants, those given vitamin D showed a significantly greater reduction in pain scores than those given a placebo. Across eight of those trials the difference in pain reduction averaged around 57%, a statistically significant result.

For ongoing joint comfort, some people pair vitamin D with our Glucosamine, Chondroitin and MSM complex, or explore the full Pain and Inflammation collection for the wider approach.

Can low vitamin D cause anxiety or low mood?

There is a real link between low vitamin D and mood, though it is more established for depression than for anxiety. Vitamin D receptors sit in the parts of the brain that regulate mood, and vitamin D helps switch on an enzyme involved in making serotonin, the neurotransmitter tied to wellbeing.

A 2025 systematic review and meta-analysis found that low blood levels of vitamin D were associated with around a 45% increase in the odds of depression across 15 studies, with very consistent findings. The picture for anxiety is weaker. Some trials show vitamin D supplementation eases anxiety symptoms in people who are deficient, while several larger reviews find no clear standalone effect.

If mental wellbeing is your focus, it is worth looking at the fuller picture. Our Mental Health support range and Magnesium Glycinate are often part of that conversation, alongside professional support.

Vitamin D deficiency and hair loss

Vitamin D helps control the hair follicle growth cycle, so a deficiency can be a factor in several types of hair loss. The vitamin D receptor plays a direct role in normal hair cycling, which is why low levels keep turning up in people who are shedding more than usual.

A 2024 systematic review and meta-analysis found that vitamin D deficiency was present in around 52% of people with alopecia areata and 50% of women with female pattern hair loss. People with alopecia areata were nearly three times more likely to be deficient than those without it, and women with female pattern hair loss were over five times more likely.

Hair health depends on more than one nutrient. Iron, zinc and biotin all matter too, which is why many people look at a broader approach such as our Biotin hair growth supplement or the wider Hair, Skin and Nails collection.

Can vitamin D deficiency cause dizziness?

It can play a part, particularly in a common type of dizziness called benign paroxysmal positional vertigo, or BPPV. This is the brief spinning sensation you get when you move your head, tip it back or roll over in bed, and it is the single most common cause of positional vertigo.

BPPV happens when tiny calcium crystals in your inner ear become dislodged, and vitamin D is closely tied to calcium balance. In one case-control study, people with recurrent BPPV had markedly lower vitamin D than those without recurrence, and a 2025 meta-analysis concluded that vitamin D supplementation can significantly lower the chance of BPPV coming back.

Can vitamin D deficiency cause weight gain?

This one needs a careful answer. Low vitamin D and higher body weight are strongly linked, but the relationship mostly runs the other way. Vitamin D is fat-soluble, so in people carrying more body fat it gets stored away in fat tissue and less stays circulating in the blood. That is why obesity is a well-established risk factor for vitamin D deficiency.

There is little good evidence that being low in vitamin D directly causes you to gain weight. What is fair to say is that deficiency, fatigue and low mood can feed into less activity and lower motivation, which affects weight indirectly. Correcting a deficiency is good for your energy and your bones, but it is not a weight-loss treatment.

If managing weight is your goal, our Diet and Digestion range sits alongside the basics of movement and a balanced diet, not in place of them.

How to get a vitamin D deficiency test

The only reliable way to know if you are deficient is a blood test. Symptoms point you in the right direction, but they overlap with too many other conditions to diagnose on their own.

What the test measures

A vitamin D test measures serum 25-hydroxyvitamin D, written as 25(OH)D, which is the accepted marker of your body's vitamin D stores. It is a simple blood sample and does not usually need fasting. The active form, 1,25-dihydroxyvitamin D, is not used for this because it does not reflect your reserves and can read misleadingly normal.

What your result means in the UK

How to get tested

• Through your GP, who can arrange a test if you have symptoms of deficiency or risk factors such as darker skin, little sun exposure, or a condition affecting absorption.

• Through a private or home finger-prick test kit, which posts your sample to a lab and returns a 25(OH)D result.

The NHS does not screen everyone, because for most at-risk people it is more cost-effective to simply take a daily supplement than to test first. If you have clear symptoms, though, testing is the sensible route.

How to raise your vitamin D levels safely

There are three ways to get more vitamin D: sunlight, food and supplements. In the UK, most people need all three at different times of year, because from October to March the sun sits too low for your skin to make any vitamin D at all.

1. Sunlight

From late March to the end of September, most people can make enough vitamin D from short daily sun exposure on bare forearms, hands and lower legs, roughly 10 to 30 minutes around midday. You need longer if you have darker skin. Never let your skin redden or burn.

2. Food

Vitamin D is found in only a few foods: oily fish such as salmon and mackerel, egg yolks, red meat and fortified foods like some cereals and spreads. Diet alone rarely provides enough, which is why supplements matter through the darker months.

3. Supplements

The NHS advises that everyone in the UK considers taking a daily 10 microgram (400 IU) supplement during autumn and winter, and all year round if you are at higher risk. If you have a confirmed deficiency, your doctor may recommend a higher dose to rebuild your stores. The safe upper limit for adults is 100 micrograms (4,000 IU) a day unless a doctor advises otherwise.

You can find it here: VitaBright Vitamin D3 4000 IU. Many people also pair it with Vitamin K2, which helps direct calcium towards the bones, in our Vitamin D3 and K2 combo.