After a nice long summer, Vitamin D deficiency isn't currently at the forefront of most people's minds. At LDC, our Doctors encourage our patients to take a pro-active approach to their health, by means of active screening and prevention of disease. This is why our GP's are always looking one step ahead as to what our patients should be considering with regard to their health in the near future.

With Winter here and the levels of sunlight dramatically decreased to an estimated daily average of just 1 hour and 15 minutes of sunlight! It's time you start to consider your Vitamin D levels.

So, without further ado, let's introduce the Vitamin of the hour: Vitamin D!

What is Vitamin D?

Vitamin D is one of 13 essential vitamins in our bodies. It has many roles from maintaining bone strength to helping immune function and preventing fatigue.

It can be obtained from the diet and is also made from sunlight exposure. Foods that are rich in vitamin D include mushrooms, egg yolks, liver and oily fish. However, it is hard to get enough vitamin D from foods alone, with the majority being made as a result of exposure to sunlight.

A type of cholesterol in the skin is made into cholecalciferol by UVB light. This is then converted into 25-hydroxycholecalciferol (calcidiol) in the liver and finally into 1α, 25-dihydroxycholecalciferol (calcitriol) in the kidneys. This is the active form of vitamin D3 and helps absorption of calcium in the gut and releases calcium/phosphate from bones if needed.

Another hormone, ‘parathyroid hormone’ from the parathryroid gland, is released if low calcium is detected and this then acts on the kidneys to increase calcitriol production and reduces kidney excretion of calcium.

How Vitamin D is made and used:

Vitamin D diagram


Key causes of low Vitamin D levels in the body:

  • Lack of intake:
    • Poor diet
    • Lack of sunlight/being too covered
    • Reduced skin intake of UV light in those with more melanin (darker skin) 
  • Lack of production of active vitamin D:
    • Liver dysfunction = less 25-hydroxylation of vitamin D
    • Reduced renal function = less 1-hydroxylation of vitamin D.
      • 25 hydroxyvitamin D is a partially active form
      • 1,25 dihydroxyvitamin D is the fully active form (vitamin D3) used to be able to help resorb calcium and phosphate

Symptoms of insufficiency/deficiency:

Patients often have no symptoms. Once the insufficiency is more severe though, some may experience fatigue, certain muscles may feel weak/painful and sometimes fractures may occur (if severe).

Vitamin D Tests:

If you or your doctor are concerned about your vitamin D levels a simple blood test can be carried out to check for 25-hydroxycholecalciferol (vitamin D):

Vitamin D Status

Vitamin D Level:



Moderate Insufficiency




Treatment for Vitamin D Insufficiency:

Currently UK guidelines state that those with levels of < 25nmol/L should begin treatment. Those with a higher risk of fractures, who have complications from insufficiency/deficiency or who are likely to continue to become more deficient should also take supplements. Such treatment usually includes:




Mild-Moderate insufficiency


Supplements in tablet form:

- May be obtained ‘over the counter’

- D2 or D3 may be given, although D3 is the preferred choice

- For maintenance 800-2000 units per day may be adequate



A loading dose of 300,000 units may be required – such as through tablets over several weeks.

An alternative is weekly/monthly intramuscular injections for 6-8 weeks too


As with all good things though, too much can be bad for you. Overtreatment/very high levels of vitamin D (>250nmol/L) may result in abnormal levels of calcium in the body (hypercalcaemia), which can lead to constipation, low moods, kidney stones and even heart arrhythmias.

Furthermore, whilst sunlight exposure can help increase production of vitamin D, there is also a fine balance between obtaining enough to make vitamin D versus increasing the risk of skin cancer! Dermatologists (skin specialists) and rheumatologists (bone, joint, muscle and autoimmune specialists) have been working together to try and come up with the ideal sunlight exposure time…until this has been decided though, supplements may, therefore, be the safer option through which to obtain enough vitamin D.

Skin cancer, Dermatology, Too much Sunlight Exposure, Vitamin D

Sunlight exposure requires a fine balance: too little can lead to Vitamin D insufficiency; too much can cause skin cancer.


Benefits of treatment:

Vitamin D may help reverse/prevent the symptoms mentioned above – fatigue, thinner bones…

More recent research also indicates that it may be beneficial for patients with inflammatory bowel conditions too. Those with IBD are often found to have low vitamin D levels – whether vitamin D came first and acted as a potential trigger for the IBD or if IBD contributed to the lower vitamin D levels is still an area of active research.

Many studies have looked at and are currently still investigating the link between Multiple Sclerosis and low vitamin D levels – hence could preventing low levels also reduce the risk of this long-term condition?

Watch this space – the many roles of vitamin D are still being investigated and more of its therapeutic/prophylactic health benefits are, no doubt, yet to be revealed!


So if you're at all concerned about your Vitamin D levels, or are suffering symptoms such as severe tiredness, book in today for a GP consultation! Our experienced doctors can investigate this by performing one or more blood tests, for Vitamin D and any other possible causes of tiredness (iron levels, thyroid function). One quick 15-minute GP appointment could make the world of difference to both your energy levels and health as a whole!


By Dr Marianne Phillips