What is vitamin D deficiency and why you should care

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Vitamin D deficiency occurs when you don’t have enough vitamin D in your body for it to function normally. We get vitamin D from spending time outside in sunlight and from the food we eat. Getting enough vitamin D can be difficult, especially if you live in a country where there isn’t much sunlight (like the UK). It can also be hard to get enough vitamin D from your diet as it is only found in a few foods. 

Low levels of vitamin D can impact both your short and long-term health. Some health issues that can occur when you have low levels of vitamin D include: 

  • Problems with your bones and muscles. Vitamin D helps your body absorb calcium, a mineral important for strong bones. It also helps to preserve muscle fibres and build strong muscles. 

A weaker immune system. Vitamin D may strengthen the immune system, meaning we are more able to fight infection and disease.

What symptoms can vitamin D deficiency cause?

Symptoms of vitamin D deficiency tend to be vague and occur slowly over a long period of time. As such you may not be aware of them or may put them down to other factors like getting older or life events. 

Some common symptoms of Vitamin D deficiency include: 

  • Muscle weakness, aches, or cramps
  • Bone or joint pain
  • Headaches
  • Fatigue (extreme tiredness and lack of energy)
  • Mood swings, low mood, and depression

To learn more about the symptoms of vitamin D deficiency, read our article, Symptoms of Vitamin D Deficiency.

What is vitamin D good for?

Vitamin D helps your body absorb calcium and phosphate, minerals we need to keep our bones and muscles healthy. Low levels of vitamin D can cause hypocalcaemia, a condition where the levels of calcium in your blood get too low. As your body tries to hold onto calcium, it can trigger a condition known as secondary hyperparathyroidism which causes symptoms like muscle weakness, fatigue, and depression. Your body also starts to take calcium from your bones faster than it can be replaced, leading to break down of your bones (known as bone demineralisation), and bone weakness which increases the risk of fractures.

Why do we need vitamin D?

Vitamin D has many functions in the body, some of which are still being understood. In addition to bone and muscle health, vitamin D appears to play an important role in the prevention of many illnesses including: 

  • Heart disease. Some research suggests that Vitamin D may play an important role in heart health by boosting immunity and reducing inflammation. Low levels of vitamin D have been linked to an increased risk of heart disease. 
  • Type 2 diabetes. Studies have shown that people with higher levels of vitamin D are less likely to develop type 2 diabetes.
  • Psychiatric disorders. Low levels of vitamin D have been linked to a range of psychiatric disorders, particularlydepression.

How to get vitamin D

There are three ways our bodies can get vitamin D:

  • Sunlight
  • Food
  • Supplements 

The majority of vitamin D is made by our bodies when we expose our skin to the sun. For some people, it can be difficult to get enough vitamin D this way, for example, if you:

  • Live in a country with limited sunlight, especially during the winter months
  • Wear clothes that cover most of your skin
  • Spend a lot of time indoors
  • Have darker skin (because darker skin protects you from the sun more than lighter skin)

It can be difficult to get sufficient vitamin D from your diet as it is only found in a small number of foods. Some dietary sources of vitamin D include:

  • Oily fish like salmon, mackerel, and herring
  • Red meat and liver
  • Egg yolks
  • Fortified foods like some cereals and spreads

For more information about foods containing vitamin D, read our article, Foods High in Vitamin D

Supplements are a great way to make sure you are getting enough vitamin D. In the UK the NHS recommends everyone over 4 years of age take a vitamin D supplement of 10mcg (400IU) between early April and late September. Breastfed babies also need a daily dose of vitamin D as breastmilk alone may not contain enough. 

If you have been diagnosed with vitamin D deficiency, your doctor will tell you how much vitamin D supplement you need to take. Taking too much vitamin D can be dangerous, so never take more than the recommended amount. 


Vitamin D is an essential nutrient for many aspects of our health, and one that many people are unaware of. In the UK 1 in 6 adults and around 20% of children have low levels of vitamin D. The good news is that vitamin D is easily diagnosed and treated with a simple blood test and vitamin D supplements. 

At Medicspot we offer an at-home vitamin D deficiency test kit. The test is delivered to your home and works by testing a small sample of blood from your finger. The results are ready in around 10 minutes with no need to send your sample to the lab or wait for your results. 

We recommend booking an online GP appointment along with your test to discuss your result and any necessary treatment.


Harvard School of Public Health: Vitamin D July 2022 (Accessed August 8th, 2022)  

PubMed: Vitamin D and cardiovascular health May 2021 (Accessed August 8th, 2022)  

PubMed: Vitamin D deficiency and secondary hyperparathyroidism in the elderly: consequences for bone loss and fractures and therapeutic implications August 2001 (Accessed August 8th, 2022)  

 NHS: Vitamin D August 3rd, 2020  (Accessed August 8th, 2022)  

Gov.UK: New review launched into vitamin D intake to help tackle health disparities April 3rd, 2022  (Accessed August 8th, 2022)  

PubMed: Vitamin D and Depression: Where is all the Sunshine?  June 2011 (Accessed August 8th, 2022)  

PubMed: Vitamin D and chronic diseases May 2017 (Accessed August 8th, 2022)  

National Health Executive: Call for evidence issued as 1 in 6 adults show low levels of vitamin D   April 4th 2022 (Accessed August 8th, 2022)