GB
Germany
France
Spain
Italy
Netherlands
Norway
Sweden
Denmark
Finland
PortugalVitamin D deficiency: symptoms, tests and who is at risk
What a vitamin D blood test result means, who is most at risk in the UK, the symptoms of real deficiency, how to get tested and how it is treated.
Vitamin D deficiency usually means a blood level of 25-hydroxyvitamin D below 25 nmol/L. Mild deficiency often causes no symptoms at all. Severe or long-lasting deficiency can cause bone pain, muscle weakness and, according to the NHS, osteomalacia in adults and rickets in children. A blood test is the only way to know, and treatment is a medical decision.
What counts as vitamin D deficiency?
Vitamin D status is measured with a blood test for 25-hydroxyvitamin D (often written 25-OH-D), the form that circulates in the blood. In the UK, results are usually read like this:
| Blood level | What it usually means |
|---|---|
| Below 25 nmol/L | Deficient |
| 25–50 nmol/L | May be inadequate for some people |
| Above 50 nmol/L | Sufficient for almost everyone |
The 25 nmol/L line comes from the Scientific Advisory Committee on Nutrition (SACN), which judged that below it the risk to bone and muscle health rises. Other countries draw the line differently – US guidance uses 30 nmol/L for deficiency, and several bodies treat 50 nmol/L as adequate. That is why two websites can give different numbers for the same result.
Who is most at risk of low vitamin D?
In the UK, low vitamin D is mostly about sunlight. Between October and early March the sun isn’t strong enough for the skin to make enough, so levels tend to be lowest in late winter. You’re more likely to be low if you:
- rarely go outdoors – for example if you’re frail, housebound or live in a care home
- usually cover most of your skin when outside
- have dark skin, for example of African, African-Caribbean or south Asian background, because it takes more sun to make the same amount
- are older – the skin makes less vitamin D with age
- rarely eat oily fish, eggs or fortified foods
- have a condition that affects how the gut handles fat, such as coeliac disease or Crohn’s disease, or have liver or kidney disease
- are living with obesity, as vitamin D is stored in body fat
What are the symptoms of not enough vitamin D?
Mild or moderate deficiency often causes no symptoms at all – many people only find out from a blood test. When deficiency is severe or goes on for a long time, the NHS lists these as the main signs of rickets in children and osteomalacia in adults:
- pain in the back, shoulders, ribs, pelvis or legs
- swollen, painful wrists
- weak muscles – for example finding it hard to climb stairs or get out of a chair
- tingling, cramping or twitching of the muscles
- changes in the way you walk, or tiring more easily when walking
- bones that break more often or after a minor accident
- in children, bowed legs, being small for their age and teeth coming through late
If you have bone pain or muscle weakness that you can’t explain, see your GP rather than trying to work it out yourself.
How do you feel when your vitamin D is low?
Usually, no different. That’s the honest answer, and it’s why online symptom lists can mislead. Tiredness, aches and low mood are common and have many possible causes – from poor sleep and stress to anaemia or an underactive thyroid. Low vitamin D can sit alongside them without being the reason.
If you’ve felt unwell for weeks, a GP can look at the whole picture and decide which tests make sense.
What organ is affected by vitamin D deficiency?
Mainly the bones and muscles. Without enough vitamin D the body can’t keep calcium and phosphate at the right levels, so bones don’t mineralise properly and become soft – that is what rickets and osteomalacia are. Muscles can become weak and painful.
The skin, liver and kidneys are where vitamin D is made and activated, so liver or kidney disease can itself be a cause of low levels.
How do I get a vitamin D test?
There are two routes:
- Through your GP. The NHS doesn’t test everyone, but your GP can order a blood test if you have symptoms such as bone pain or muscle weakness, a condition that affects vitamin D, or a high risk of deficiency.
- A home test kit. Private labs and pharmacies sell finger-prick tests that you post back for analysis. They measure the same 25-hydroxyvitamin D. Discuss a low result with your GP rather than acting on it alone.
Remember the season: a test in February will usually read lower than the same person’s test in September.
How is vitamin D deficiency treated?
A confirmed deficiency is treated by a doctor. For severe deficiency, GPs commonly prescribe a course of higher-dose vitamin D, followed by an everyday maintenance dose, and sometimes calcium. The dose and length depend on your blood level, your symptoms and any other conditions, and your GP may recheck your level and your calcium afterwards.
Don’t try to fix a low result quickly with large over-the-counter doses. High doses taken without supervision can push calcium in the blood too high – see Can you take too much vitamin D?
How can you raise vitamin D levels?
There’s no safe shortcut, but there are three steady ways:
- Sunlight from late March to September. The NHS suggests about 15 minutes outdoors without sunscreen 2 or 3 times a week, and more often if you have brown or black skin – always covering up or going into the shade before you start to burn.
- Food – oily fish, eggs, red meat and fortified foods. See Vitamin D foods and sunlight.
- A daily supplement in line with UK advice – see How much vitamin D per day?
If you have a diagnosed deficiency, follow the dose your doctor gives you.
Frequently asked questions
What are three symptoms of not enough vitamin D?
In severe or long-lasting deficiency, the NHS lists bone pain (often in the back, shoulders, ribs, pelvis or legs), muscle weakness such as difficulty climbing stairs, and tingling, cramping or twitching of the muscles. Mild deficiency often has no symptoms at all.
How do you feel when your vitamin D is low?
Often no different. Tiredness, aches and low mood are common and have many causes, so they aren’t a reliable sign of low vitamin D on their own. A blood test is the only way to know.
What organ is affected by vitamin D deficiency?
Mainly the bones and muscles. Without enough vitamin D, bones can become soft (osteomalacia in adults, rickets in children) and muscles can become weak and painful.
How to raise vitamin D quickly?
If you have a confirmed deficiency, your GP will prescribe the right dose – often a short higher-dose course. Don’t take large doses on your own, as too much vitamin D can raise calcium in the blood.
How do I get a vitamin D test?
Ask your GP if you have symptoms or a high risk of deficiency, or use a private finger-prick home test. Talk through a low result with your GP before changing what you take.
What vitamin D level is too low?
In the UK, a 25-hydroxyvitamin D level below 25 nmol/L is usually classed as deficient, and 25–50 nmol/L as possibly inadequate. Some countries use 30 nmol/L as the cut-off for deficiency.
