Vitamin D is essential for bone health, calcium absorption, and muscle function. In the UK, the recommended daily intake is 10 micrograms (400 IU) for most adults and children over one year. Due to limited sunlight exposure, particularly during autumn and winter months, the Department of Health and Social Care advises that everyone should consider taking a daily supplement containing 10 micrograms of vitamin D. Certain groups, including those with darker skin tones, limited sun exposure, or specific medical conditions, may require year-round supplementation. Understanding how much vitamin D you need helps maintain optimal bone and muscle health whilst avoiding deficiency.

Recommended Daily Vitamin D Intake in the UK

In the United Kingdom, the recommended daily intake of vitamin D is 10 micrograms (400 IU) for most adults and children over the age of one year, as advised by the Department of Health and Social Care and the Scientific Advisory Committee on Nutrition (SACN). This recommendation is designed to maintain adequate bone and muscle health in the general population.

Vitamin D is essential for calcium absorption and bone mineralisation, playing a critical role in preventing conditions such as rickets in children and osteomalacia in adults. The UK's northerly latitude means that sunlight exposure—the primary natural source of vitamin D—is insufficient for adequate synthesis during autumn and winter months (October to March). Even during summer, factors such as cloud cover, indoor lifestyles, and appropriate sun protection practices can limit vitamin D production.

The Department of Health and Social Care recommends that everyone should consider taking a daily supplement containing 10 micrograms of vitamin D during the autumn and winter months (October to March). Some individuals should consider year-round supplementation, particularly those with limited sun exposure, those who cover their skin when outdoors, or those with darker skin tones, which reduce the skin's ability to synthesise vitamin D from sunlight.

Whilst dietary sources such as oily fish (salmon, mackerel, sardines), egg yolks, and fortified foods (breakfast cereals, fat spreads) contribute to vitamin D intake, it is challenging to obtain sufficient amounts through diet alone. The 10 microgram daily recommendation represents a safe and effective baseline for maintaining vitamin D sufficiency across the UK population, primarily supporting skeletal health and muscle function.

How Much Vitamin D Do Different Age Groups Need?

Vitamin D requirements vary slightly across different life stages, though the core recommendation of 10 micrograms (400 IU) daily applies to most age groups in the UK. Understanding these nuances helps ensure appropriate supplementation for vulnerable populations.

Infants and young children have specific needs. Babies from birth to one year of age require 8.5 to 10 micrograms daily. The NHS recommends that breastfed babies receive a daily vitamin D supplement of 8.5 to 10 micrograms from birth, as breast milk alone does not provide sufficient vitamin D. Formula-fed infants consuming at least 500ml of infant formula per day do not need additional vitamin D supplements, as formula is already fortified with vitamin D. Children aged one to four years should receive a daily 10 microgram supplement to support bone growth and development. Eligible families may access free supplements through the Healthy Start scheme.

Children over 4 years, adolescents and adults require 10 micrograms daily. This includes teenagers experiencing growth spurts, adults of working age, and older adults. There is no official increase in the recommended amount for pregnancy or breastfeeding in the UK, though maintaining adequate vitamin D status is particularly important during these periods for both maternal and foetal bone health.

Older adults (aged 65 and over) should prioritise vitamin D supplementation, as ageing reduces the skin's capacity to synthesise vitamin D and many older people have reduced sun exposure. The 10 microgram daily recommendation remains consistent, but adherence is especially important in this group to maintain bone and muscle health, which may help reduce fall risk. Vitamin D alone does not prevent fractures, but correcting deficiency is an important part of bone health management.

Individuals in care homes or those who are housebound should take vitamin D supplements daily throughout the year, as their sun exposure is typically minimal.

When You Might Need More Vitamin D

Certain individuals and clinical circumstances may warrant higher doses of vitamin D supplementation beyond the standard 10 microgram daily recommendation. These situations should be discussed with a GP or healthcare professional, who may recommend testing your vitamin D levels before prescribing higher doses.

People with darker skin tones (African, African-Caribbean, or South Asian backgrounds) have higher concentrations of melanin, which reduces the skin's ability to produce vitamin D from sunlight. These individuals are at increased risk of deficiency and may benefit from year-round supplementation at the standard 10 microgram dose, or higher doses if deficiency is confirmed by blood testing.

Individuals with limited sun exposure include those who cover their skin for cultural or religious reasons, people who are housebound or institutionalised, and those who work night shifts or spend most daylight hours indoors. These groups cannot rely on sunlight for vitamin D synthesis and should maintain consistent supplementation throughout the year.

Medical conditions affecting vitamin D absorption require particular attention. Conditions such as Crohn's disease, coeliac disease, chronic pancreatitis, and cystic fibrosis impair fat absorption, which is necessary for vitamin D uptake. Similarly, individuals who have undergone bariatric surgery or bowel resection may require higher doses. Chronic kidney disease and liver disease can affect vitamin D metabolism, but active vitamin D analogues such as alfacalcidol or calcitriol are only prescribed under specialist supervision for specific conditions and are not used for routine vitamin D deficiency.

Obesity (BMI >30 kg/m²) is associated with lower circulating vitamin D levels, as the vitamin is sequestered in adipose tissue. Some evidence suggests that individuals with obesity may require higher doses to achieve adequate serum levels, though specific UK guidance on dosing is limited.

Medications including anticonvulsants (phenytoin, carbamazepine), glucocorticoids, rifampicin, and some antiretroviral drugs can increase vitamin D metabolism. If you are taking these medications long-term, discuss vitamin D supplementation with your GP, who may recommend blood testing to assess your vitamin D status and determine appropriate supplementation. Do not exceed 100 micrograms (4,000 IU) daily unless prescribed and monitored by a healthcare professional.

Signs You May Not Be Getting Enough Vitamin D

Vitamin D deficiency can be subtle and develop gradually, with many people experiencing no obvious symptoms initially. However, prolonged or severe deficiency can manifest in various ways affecting bone health, muscle function, and general wellbeing.

Bone and muscle symptoms are the most characteristic features of vitamin D deficiency. Adults may experience bone pain, particularly in the lower back, pelvis, and legs, alongside muscle weakness and generalised aching. These symptoms reflect the underlying osteomalacia (softening of bones) that occurs when vitamin D deficiency impairs calcium absorption and bone mineralisation. In children, severe deficiency causes rickets, characterised by delayed growth, bone deformities (bowed legs, knock knees), delayed tooth development, and skeletal pain.

Fatigue and low mood have been associated with low vitamin D levels in some studies, though the evidence linking vitamin D deficiency directly to these symptoms remains under investigation. These symptoms are non-specific and can have many other causes.

Increased susceptibility to infections may occur, as vitamin D plays a role in immune function. Some research suggests that vitamin D deficiency might be associated with more frequent respiratory infections, though this relationship requires further study and is not proven for the general population.

Stress fractures and reduced bone density can develop over time in those with chronic deficiency, particularly in older adults and postmenopausal women already at risk of osteoporosis.

Red flags requiring urgent assessment include bone deformities in children, recurrent low-trauma fractures, severe bone pain, and significant proximal muscle weakness.

Routine screening for vitamin D deficiency is not recommended for asymptomatic, low-risk adults. If you experience persistent bone pain, muscle weakness, unexplained fatigue, or recurrent fractures, contact your GP. A blood test measuring serum 25-hydroxyvitamin D levels can confirm deficiency. In the UK, levels below 25 nmol/L indicate deficiency, 25-50 nmol/L suggests insufficiency, and levels above 50 nmol/L are generally considered adequate for most people. Your GP can then recommend appropriate supplementation doses based on your results.

Safe Upper Limits and Vitamin D Toxicity

Whilst vitamin D supplementation is generally safe at recommended doses, excessive intake can lead to toxicity, known as hypervitaminosis D. Understanding safe upper limits is essential to avoid potential harm whilst ensuring adequate supplementation.

The safe upper limit for vitamin D in the UK, as established by the European Food Safety Authority (EFSA) and recognised by the NHS, is 100 micrograms (4,000 IU) daily for adults, including pregnant and breastfeeding women. For children, the upper limits are lower: 25 micrograms (1,000 IU) for infants up to 12 months, 50 micrograms (2,000 IU) for children aged 1-10 years, and 100 micrograms (4,000 IU) for those aged 11-17 years. These limits represent long-term daily intake levels that should not be exceeded unless prescribed and monitored by a healthcare professional.

Vitamin D toxicity does not occur from sun exposure or normal dietary intake; it results exclusively from excessive supplementation. Toxicity causes hypercalcaemia (elevated blood calcium levels), which can manifest as:

• Gastrointestinal symptoms: nausea, vomiting, poor appetite, constipation, and abdominal pain

• Neurological effects: confusion, disorientation, and in severe cases, altered consciousness

• Renal complications: excessive thirst, frequent urination, dehydration, and potentially kidney stones or kidney damage

• Cardiovascular effects: abnormal heart rhythms due to elevated calcium levels

Harm can occur at different doses for different individuals, and certain medical conditions (such as sarcoidosis, tuberculosis, and some lymphomas) can increase sensitivity to vitamin D. Be cautious about taking multiple supplements containing vitamin D (such as multivitamins plus separate vitamin D supplements) to avoid unintentionally exceeding safe limits.

If you are taking high-dose vitamin D supplements prescribed by a healthcare professional for confirmed deficiency, monitoring typically includes checking calcium levels (and possibly renal function) at baseline and after about one month, with vitamin D levels rechecked after 3-6 months. Never exceed recommended doses without medical supervision. If you experience symptoms suggestive of hypercalcaemia whilst taking vitamin D supplements, stop the supplement and contact your GP promptly for assessment and blood testing.

If you suspect an adverse reaction to a vitamin D supplement or medicine, you can report it to the MHRA Yellow Card scheme (yellowcard.mhra.gov.uk or via the Yellow Card app).

Frequently Asked Questions