Vitamin D helps control calcium and phosphate in the body, keeping bones, teeth and muscles healthy. A lack of vitamin D in the UK can cause many symptoms such as tiredness, depression and aches and pains. 

Vitamin D is responsible for increasing intestinal absorption of calcium, iron, magnesium, phosphate and zinc. In humans, the most important types of Vitamin D are vitamin D3 and vitamin D2. 

Vitamin D3 is naturally produced in the human skin through exposure to sunlight and Vitamin D2 is mainly obtained from foods. Vitamin D is transported to the liver where it is metabolised to 25-hydroxy Vitamin D. 

In medicine, a 25-hydroxy Vitamin D blood test is used to determine Vitamin D concentration in the body. The blood concentration of 25-hydroxy Vitamin D (including D2 and D3) is considered the best indicator of Vitamin D status. Vitamin D deficiency is now recognised as a global epidemic. Virtually every cell in our body has receptors for Vitamin D, meaning that they all require a “sufficient” level of Vitamin D for adequate functioning.

Those who follow a strict vegan diet may suffer from a vitamin D deficiency because most of the natural dietary sources are animal-based, including fish and fish oils, egg yolks, fortified milk, and red meat. 

A very common cause of Vitamin D deficiency in the UK is low levels of sunlight. Because the body makes vitamin D when your skin is exposed to sunlight, anyone who lives in the UK may be at risk of deficiency During the winter, vitamin D deficiency can be more prevalent because there is even less sunlight. 

If you have darker skin, the pigment melanin shields the body from sunlight, which means that your body is unable to make sufficient levels of Vitamin D if you live in countries without much sunlight. People of South Asian and African descent who live in the UK are suffering from an epidemic of Vitamin D deficiency. This can be compounded by cultures that require covering the face and body and where people spend less time outside.

Severe lack of vitamin D causes rickets, which presents in children as abnormal growth patterns, weakness in muscles, pain in bones and deformities in joints; however, this is very rare. Children who are deficient in vitamin D can also have muscle weakness or sore and painful muscles. 

A lack of vitamin D is not quite as obvious in adults but possible signs and symptoms might include: fatigue, bone pain, muscle weakness, muscle aches, muscle cramps and depression.

• Deficient: Two distinct coloured lines will appear. One is in the control region (C) and another should be in the test region (T). The line intensity in the test region (T) will be equal to or darker than the 10ng/mL line depicted on the colour card provided with the kit. This means that you have very low levels of Vitamin D. 
• Insufficient: Two coloured lines will appear. One is in the control region (C) and another should be in the test region (T). The line intensity in the test region (T) will be darker than the 30 ng/mL line depicted on the colour card provided with the kit and lighter than the 10 ng/mL line depicted on the colour card. This means that you have slightly low levels of vitamin D and only need treatment if you have symptoms. 
• Sufficient: Two coloured lines will appear, one line will be in the control region (C) and a faint coloured line will appear in the test region (T). The line intensity in the region (T) will be equal to or lighter than the 30 ng/mL line depicted on the colour card. This means that you have normal levels of vitamin D in your bloodstream. 
• Excess: One coloured line will appear in the control line region (C). No apparent coloured line will show in the test line region (T). This means that you have high levels of Vitamin D in your bloodstream, which may be unsafe. You should stop taking any Vitamin D or multivitamin supplements. 
• Invalid: The control line will fail to appear. This could be due to insufficient specimen volume or incorrect procedural techniques. In this instance, you should take another test.