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Pack of 15 Fultium® D3 cholecalciferol 20000 IU capsules
Prescription Vitamin D
  • For seasonal vitamin D deficiency
  • To stay healthy during winter
  • Available in two doses for prevention and treatment
Prices start from £18.99 Prices and product information

Vitamin D Deficiency

Vitamin D deficiency, often referred to by its medical term hypovitaminosis D, is a condition many experience across the globe. It is particularly prevalent in colder countries that get less sunlight throughout the year. In fact, according to the National Diet and Nutritional Survey, nearly half of the UK population Trusted source University of Birmingham Educational Institution Multidisciplinary Research and Education Go to source do not get enough vitamin D.

Vitamin D helps keep our bones, teeth and muscles strong but ongoing research has found it has been linked to all aspects of our health, such as our skin and heart health. So, the government recommends most people should be taking vitamin D daily, especially during the colder months.

Getting vitamin D from enough sunlight or from your diet isn’t essential every day, but a prolonged lack of vitamin D can cause some health problems. That’s why it’s recommended many should take Vitamin D supplements. They are widely available over-the-counter, but high-dose prescription-only vitamin D capsules are often more effective for some.


Medically reviewed by Dr. Anand Abbot MRCGP Written by our editorial team Last reviewed 19-11-2023

What is vitamin D?

Vitamins are nutrients that your body needs in small amounts to regulate and maintain different bodily functions. There are 13 main vitamins that your body needs, that are all responsible for different processes in your body. We get most of our vitamins from the foods we eat, just like other essential nutrients such as fibre or carbohydrates. One of these 13 essential nutrients is vitamin D, the ‘sunshine vitamin’. There are several types of vitamin D, but the most important two are vitamins D3 and D2.

Vitamin D3 (cholecalciferol) is found naturally in several foods such as oily fish, liver and egg yolk. It is also manufactured naturally by our body from sun exposure. When your skin is exposed to sunlight, the sun’s ultraviolet B (UVB) rays convert chemical compounds in your skin known as 7-DHC into vitamin D3.

Vitamin D2 (ergocalciferol) is the other main type, but is found in much fewer foods. It is generally only found in plant-based foods such as mushrooms that have been exposed to sunlight. Vitamin D overall, is not found naturally in many foods so many food manufacturers add both vitamin D3 and D2 to their products, including milk, butter, yoghurts and cereals.

Why do we need vitamin D?

Vitamin D is essential for bone development, this is because it helps the body absorb calcium and phosphates from our diet. Low levels of vitamin D, and therefore a lack of calcium (hypocalcemia), often leads to several conditions and deformities of the bones that cause bone pain, poor growth, weak bones and bone density loss.

It is mainly responsible for bone health, but it is possible vitamin D is linked to other conditions including mental health disorders, cardiovascular diseases (like heart disease), migraine & chronic headaches, as well as other processes in the immune system. Experts suggest low levels of vitamin D can also be linked to breast cancer. Overall, vitamin D is very much an important nutrient for a healthy body and mind.

What causes a vitamin D deficiency?

There are two main factors in vitamin D deficiency. The first is diet. If you don’t eat many foods in your diet that contain vitamin D then you may develop a deficiency. This is especially true for those who do not eat meat, eggs or dairy, as these are the main foods that have been fortified with vitamin D.

The other main contributing factor is sunlight exposure. During colder times of year, particularly between October and March (in the northern hemisphere), the sun appears less frequently and sets earlier in the day.

This also affects those with darker skin tones, such as those who have an African, African-Caribbean or south Asian background. This is because those with dark skin have more of a pigment called ‘melanin’ in their skin, which reduces the body’s ability to synthesise vitamin D from the sun.

A few groups of people have been found to be at a high risk of developing a vitamin D deficiency. Risk factors include those who:

  • are over 55 years of age
  • are pregnant
  • have a family history of vitamin D deficiency
  • have and inflammatory bowel disease, such as Crohn’s disease, ulcerative colitis or celiac disease
  • have a history of liver disease
  • have a history of kidney disease
  • are lactose or gluten intolerant
  • are vegan or vegetarian
  • have a high BMI
  • take certain medications including weight-loss drugs like Xenical (Orlistat) and oral steroids like prednisone

What are the symptoms of a vitamin D deficiency?

There are no telltale symptoms that you have low vitamin D. If you do have symptoms, they’re probably very subtle.

Symptoms may include:

These symptoms could indicate many conditions, so it’s important to speak to a healthcare professional if you experience any worrying or severe symptoms.

What are the risks of vitamin D deficiency?

Vitamin D deficiency can result in some medical conditions in the long-term. One of these conditions is known as hyperparathyroidism. This is a condition that affects the parathyroid glands in your neck that help to control calcium levels in your blood. When there are low levels of vitamin D, less calcium is absorbed into your digestive system. This causes the parathyroid glands to become overactive and extract the calcium from your bones and into your bloodstream (hypercalcemia). This affects your kidneys, as well as your bones, which can result in nausea, dehydration and high blood pressure.

The condition also causes the bones to soften over time, leading to bone pain and potentially deformities. Your bones will weaken over time (osteoporosis) meaning you are more susceptible to fractures and breaks from falls. Low vitamin D can also lead to defective bone mineralisation over time which means the quality of your bone tissue may be compromised. This will result in several bone diseases including ‘osteomalacia’ in adults and ‘rickets’ in children, where the bones break-down faster due to the lack of nutrients for healthy bone tissue.

How do I treat vitamin D deficiency?

Diet & lifestyle

One way you can increase your vitamin D intake is to spend more time outside. Most people can get the right amount of vitamin D from daily short periods in the sun with their hands, forearms or lower legs uncovered. However, you should still take care to not burn from prolonged exposure, as this can lead to many skin conditions including skin cancer. Make sure to protect your skin from burning by wearing sun cream, especially during the summer months.

Although there are not many vitamin D-rich foods, there are a select few foods that are good sources of vitamin D and thereby improve your vitamin D levels:

  • oily fish - salmon, mackerel, herring and sardines
  • red meat - including liver
  • eggs
  • fortified foods including dairy products, spreads and cereals


It’s difficult to get your recommended vitamin D intake solely from food, so most people will need to take supplements. These are available over-the-counter and on prescription. Supplements typically contain the active form of vitamin D3 known as cholecalciferol (25-hydroxyvitamin D) and are measured in international units (IU), in which 1 microgram of vitamin D is equivalent to 40IU.

For general daily maintenance of vitamin D levels, the optimal dose is 400IU a day (equivalent to 10 micrograms) for most people, including pregnant women, older adults and children. Vitamin D capsules in this strength are widely available over-the-counter, in the form of tablets, liquid drops and an oral solution.

If you have a vitamin D deficiency, either during winter or for other reasons, you may require high-dose vitamin D tablets. You can take a higher dose of vitamin D at around 10 - 20,000IU (400mcg) and these are available over-the-counter (on advice by a pharmacist) or on prescription.

It’s important that you do not take more than the recommended daily amount off the dose you have been prescribed. Whilst they are generally very safe and there tend to be very few side effects of vitamin D, too much vitamin D does not provide any greater benefits and can cause adverse effects (vitamin D toxicity). The prevalence of severe effects is low, but vitamin D doses should be adhered to.

How do I buy treatment online?

You can buy prescription vitamin D3 capsules (Fultium) in 800IU and 20,000IU doses here at HealthExpress for preventing or treating a vitamin D deficiency. All you have to do is complete a quick online consultation which will be reviewed by one of our registered doctors. Once approved for treatment, our pharmacy will dispense and dispatch your medication with free, next-day delivery.

Do I need to get tested for vitamin D deficiency?

You do not need to get tested for vitamin D levels if you want to buy either the 800IU or 20,000IU dose at HealthExpress. However, you cannot purchase more than one course of the 20,000IU capsules a year without a vitamin D test.

It’s recommended you speak with your doctor if you regularly experience symptoms of a vitamin D deficiency, as they will want to test your vitamin D levels to make sure there’s nothing else causing your symptoms.

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