Last updated: October 2026
Many people with low vitamin D have no symptoms. When signs appear, the main ones are bone pain (often in the back, ribs, pelvis or legs), aching or weak muscles, and in children, bowed legs from rickets. Tiredness and low mood are often blamed but have many causes. A GP blood test is the only way to know.
Below: how reliable each sign is, who is most at risk in the UK, how the blood test works and how GPs treat a deficiency.
The short version: vague symptoms are a reason to see your GP, not a reason to start high-dose vitamin D on your own. For everyday prevention, the NHS advice is simple: 10 micrograms a day in autumn and winter. Our vitamin D in winter guide explains the daily dose in full.
Signs of low vitamin D
Vitamin D helps the body control calcium and phosphate, so the clearest signs of a real deficiency show up in bones and muscles. Online lists often include a dozen or more symptoms, but the evidence behind them varies a lot.
| Sign | How strong is the link? | Other common causes |
|---|---|---|
| Bone pain or tenderness (back, ribs, pelvis, legs) | Strong, especially when it has gone on for months | Arthritis, injury, joint pain from other causes |
| Muscle aches, cramps or twitching | Strong when severe and long-lasting | Exercise, low magnesium, dehydration |
| Weak thigh and hip muscles (struggling with stairs or getting up from a chair) | Strong, a typical sign of osteomalacia | Thyroid problems, ageing, inactivity |
| Bowed legs, late teeth or slow growth in children | Strong, the main signs of rickets | Needs a doctor to assess |
| Bones that break easily | Moderate, linked to long-term low levels | Osteoporosis, low calcium |
| Tiredness | Weak on its own | Iron deficiency, low B12, thyroid, poor sleep |
| Low mood in winter | Weak; mood has many causes | Winter blues, SAD, stress |
| Hair loss | Weak; not well established | Stress, iron, thyroid, hormones |
| Getting ill often | Weak; immunity depends on many things | Poor sleep, stress, young children at home |
Vitamin D contributes to the maintenance of normal bones and to normal muscle function, which is why bone and muscle signs are the ones doctors take most seriously.
Vitamin D deficiency and tiredness
Low vitamin D and tiredness both peak in late winter, so it is easy to link them. But tiredness has many causes, from poor sleep and stress to iron deficiency, low B12 and an underactive thyroid. See why am I always tired? and why am I so tired in winter?
The research is limited. One Swiss trial gave 120 otherwise healthy adults who were both tired and low in vitamin D either a single large dose of vitamin D3 or a placebo. After four weeks, fatigue scores improved more in the vitamin D group. It was small and short, and it only included people with a confirmed deficiency.
If you are tired all the time, ask your GP to check the usual causes together rather than assuming it is vitamin D. Vitamin D has no authorised health claim for tiredness. For what does have evidence, see the best supplements for energy.
Vitamin D deficiency in women and men
The symptoms are the same for both sexes. What differs is when the risk is higher.
- Pregnancy and breastfeeding: a higher-risk time, and the NHS advises 10 micrograms a day. Ask your midwife or GP which product to use. We don’t recommend our products during pregnancy or breastfeeding.
- Covering your skin: women who cover most of their skin outdoors make less vitamin D and are advised by the NHS to take it all year.
- Midlife: aches, tiredness and low mood around the menopause have many possible causes. See perimenopause symptoms.
- Men: UK survey data show low vitamin D is slightly more common in men than in women.
Who is at risk of low vitamin D in the UK?
Low vitamin D is common here. In the UK National Diet and Nutrition Survey (2019 to 2023), 18% of adults aged 19 to 64 and 12% of those aged 65 and over had blood levels below 25 nmol/L, and the figure rose to between 21% and 38% from January to March. Between October and early March, the sun in the UK is too weak for your skin to make enough.
You are more likely to be low if you:
- have darker skin, for example an African, African-Caribbean or south Asian background
- are rarely outdoors, for example if you are frail, housebound or live in a care home
- usually cover most of your skin when outside
- are 65 or over
- are pregnant or breastfeeding
- have a BMI over 30
- have a condition that affects fat absorption (such as coeliac or Crohn’s disease), have had weight loss surgery, or have severe liver or kidney disease
- take certain medicines that lower vitamin D (ask your pharmacist)
Babies and children: the NHS advises a daily vitamin D supplement for all children aged 1 to 4, and for babies who are breastfed or have less than 500ml of formula a day. Ask your health visitor or pharmacist which product to use. Our products are for adults only.
Rickets and osteomalacia
A long-term lack of vitamin D and calcium can make the bones soft and weak.
- Rickets (children): the main sign is bowed legs. Children may also be small for their age, and their teeth may come through later than usual.
- Osteomalacia (adults): bone pain, weak muscles that make walking, climbing stairs or getting out of a chair harder, and bones that break more easily, especially in the hips, lower back and feet.
A GP checks vitamin D and calcium with a blood test, and a specialist may arrange X-rays or a bone scan. Treatment is usually vitamin D and calcium supplements under medical supervision.
How to test your vitamin D level
The test measures 25-hydroxyvitamin D, written 25(OH)D, which reflects your vitamin D over the past few weeks. A GP will usually test if you have bone pain, muscle weakness, widespread aches or a bone condition. NICE advises against routine testing in people without symptoms; people at higher risk should simply take a daily supplement.
| Blood level of 25(OH)D | What it means (UK thresholds for bone health) |
|---|---|
| Below 25 nmol/L | Higher risk of deficiency |
| 25 to 50 nmol/L | May be inadequate (insufficient) for some people |
| Above 50 nmol/L | Enough for most people |
These thresholds come from the Scientific Advisory Committee on Nutrition (SACN). Home finger-prick kits measure the same marker, but a result on its own is not a diagnosis. If yours is low, see your GP rather than treating yourself with high doses.
How vitamin D deficiency is treated
Treating a confirmed deficiency is different from the everyday 10 micrograms the NHS advises for prevention.
| Everyday prevention | Treating a diagnosed deficiency | |
|---|---|---|
| Who decides | You, following NHS advice | Your GP or specialist |
| Typical amount | 10 micrograms (400 IU) a day | A loading course totalling about 300,000 IU over 6 to 10 weeks, then a maintenance dose |
| Maintenance | Not needed | 800 to 2,000 IU (20 to 50 micrograms) a day, starting about a month after loading |
| Checks | None | Calcium intake reviewed; some people need blood tests |
NICE guidance says GPs use a loading course when a deficiency needs correcting quickly, for example when someone has symptoms; otherwise they may start straight on a maintenance dose. Vitamin D3 is the preferred form. People with kidney stones, severe kidney or liver disease or problems absorbing fat may need specialist advice first, and your GP will check you get at least 700mg of calcium a day.
Never copy a loading dose on your own. Afterwards, most people buy a maintenance supplement over the counter. See how much vitamin D to take in the UK.
Can you take too much vitamin D?
Yes, from supplements, though not from sunlight. The NHS says taking too much over a long time can cause calcium to build up in the body (hypercalcaemia), which can weaken bones and damage the kidneys and heart.
- Adults and children aged 11 to 17: no more than 100 micrograms (4,000 IU) a day
- Children aged 1 to 10: no more than 50 micrograms (2,000 IU) a day
- Babies under 12 months: no more than 25 micrograms (1,000 IU) a day
Add up everything you take, including multivitamins, unless your doctor has prescribed a higher dose for a set time.
Preventing low vitamin D
The NHS advises everyone to consider 10 micrograms a day from October to March, and some groups all year. Add time outdoors from late March to September (without burning), the few foods that contain vitamin D, such as oily fish and egg yolks, and calcium from dairy and leafy greens. Many people pair vitamin D with magnesium in winter. See magnesium and vitamin D together and our winter wellness guide.
If you use CBD oil, our Evolabs Mint CBD Oil with vitamin D3 adds 5 micrograms of vegan, algae-based D3 per half pipette (100% of the nutrient reference value) to broad spectrum CBD. Vitamin D contributes to the normal function of the immune system, the maintenance of normal bones and normal muscle function. It is a daily top-up for adults, not a treatment for a diagnosed deficiency, so follow your GP’s plan and count it in your daily total. Read why we added vitamin D3 to our mint oil.
The FSA’s 10mg a day figure is precautionary advice rather than a legal limit, set while longer-term safety research continues. At Evopure we think it is a very cautious figure, and many adults use more. If you go above it, increase slowly, and check with your GP or pharmacist first if you take any medication.
When to see a GP
See a GP if you have:
- bone pain, or aching muscles that don’t settle
- muscle weakness, such as struggling to climb stairs or get up from a chair
- a bone that broke after a minor fall or knock
- tiredness or low mood that has lasted more than a few weeks
- a child with bowed legs, delayed teeth or slow growth
Your GP can check vitamin D alongside iron, B12 and thyroid levels. See underactive thyroid symptoms and low mood vs depression.
FAQs
What are the first signs of vitamin D deficiency?
Often there are none. When symptoms appear, they are usually bone pain, aching muscles and muscle weakness. In children, the first sign of rickets is often bowed legs.
Can low vitamin D make you tired?
It can be one cause, but tiredness has many others, such as poor sleep, iron deficiency, low B12 and thyroid problems. A GP blood test can check these together.
What level of vitamin D is classed as deficient in the UK?
A blood level of 25(OH)D below 25 nmol/L means a higher risk of deficiency. Between 25 and 50 nmol/L may be insufficient for some people, and above 50 nmol/L is enough for most.
How long does it take to fix low vitamin D?
A GP loading course usually runs for 6 to 10 weeks, followed by a daily maintenance dose. Symptoms such as bone pain can take longer to improve.
Can I treat vitamin D deficiency myself?
No. A daily 10 microgram supplement helps prevent low levels, but a diagnosed deficiency needs a plan from your GP, which may include higher doses for a set time.
Who should take vitamin D all year in the UK?
The NHS advises it for people who are rarely outdoors, who cover most of their skin outside, or who have dark skin, plus children aged 1 to 4 and most babies.
Sources
- NHS. Vitamin D.
- NHS. Rickets and osteomalacia.
- NICE Clinical Knowledge Summaries. Vitamin D deficiency in adults (definition, risk factors, prevalence, diagnosis and management; revised August 2026).
- Nowak A et al (2016). Effect of vitamin D3 on self-perceived fatigue: a double-blind randomized placebo-controlled trial. Medicine (Baltimore).
- Food Standards Agency. Cannabidiol (CBD) guidance.
This guide is general information, not medical advice. Evopure makes the Evolabs Mint CBD Oil with vitamin D3.
