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How do I know if I am getting enough vitamin D?

How do I know if I am getting enough vitamin D?

Vitamin D is an essential vitamin. Our bodies produce it when the skin is exposed to sunlight and we can also access the vitamin in a limited way through some foods. If it’s not already part of your supplement regime, read on to consider if you need to top up. 

What is vitamin D’s function in the body? 

Vitamin D’s most understood purpose is the support of healthy bones and teeth, chiefly due to its ability to enable calcium and phosphate absorption. This relationship between vitamin and calcium is central to lots of clinical studies and is referenced in just about all articles you can read on the subject.  

Some scientists have been interested in vitamin D’s potential in other areas of health and this has led to a large number of studies over the past few decades. Researchers have hypothesised that vitamin D also promotes the function of the immune system, contributes to heart and muscle health and that it may even have a role to play it battling some auto-immune disorders.  


Am I deficient? 

Vitamin D deficiency is a medical condition that can only be confirmed by a blood test. It is not common to have severe vitamin D deficiency in Britain today. 

In one of its numerous articles on the subject, Harvard Medical School1 suggests that, instead of speculating about deficiency, we consider if this vitamins levels are insufficient for optimal health. This may sound like semantics but it’s a more complex topic than it first seems.  

Depending on your age, lifestyle, diet, skin tone, weight and other medical conditions, an insufficiency of vitamin D is far more likely than a severe vitamin deficiency. 

It’s worth adding that both vitamin K and magnesium2 both help the body to utilise the calcium that vitamin D helps to unlock 


How to get vitamin D from the sun in Britain 

At latitude 51° North, southern England gets more than its fair share of British sunshine but even these balmy climates get relatively little sunny brightness if you’re aiming to get enough vitamin D. 

The NHS states that most children and adults in Britain should get the vitamin D they need from late March to September3 purely by being exposed to the sun. However, this is Britain with unpredictable weather and a population that’s typically adverse to flashing much flesh. 

If you can get out in the sun frequently, then some decent exposure to UBV rays will enable your skin to produce over 10,000 IU of Vitamin D each day.  


Consider which of these descriptions best reflects you: 


Profile 1 

Profile 2 


20s – 30s 



Roofer on building sites 

Work in an office all day 


I’m always out training for my next triathlon 

go to the gym occasionally but only very occasionally. 


I eat everything and am pretty healthy 

I could be more varied but I’m not eating fish, no way 

Body mass 

My abs are not bad at all 

would like to lose a few pounds 


Generally good 

I take some daily medication  

Skin Exposure 

Am normally in just shorts and work boots through the summer 

I may show an ankle or two, more if I’m by a pool in Spain 


More likely to generate adequate Vitamin D 

Less likely to generate adequate Vitamin D 


If Profile 1 is more reflective of you, you’re well on your way to getting enough of the shining vitamin but keep enjoying the good weathereat oily fish maybe twice a week and stay safe in the sun. 

If you recognise yourself in Profile 2, further steps may be required to ensure your Vit D levels are sufficient for optimal health. Ageing skin is less effective at making Vitamin D and too many fat cells can store Vit D but make it difficult for the body to use.  


When is the best time to get vitamin D from the sun?  

Vitamin D3 is the form that is produced via sunlight, as opposed to Vitamin D2produced by some plants that we eat.  

To access free vitamin D3 in Britain, exposing the skin to UVB rays is required; they’re the ones that we get when the sun is highest and brightestGetting out in the sun between 11am and 3pm during the spring and summer gives you your best chance of catching the right rays. Just 10 – 20 minutes each day should be adequate for your skin to produce over 10,000 IU. 

As ever, take care in the sun4. UVB rays are powerfulare the cause of sunburn and they contribute to some skin cancers.  The dilemma is that if you use sunscreen, it limits how many UVB rays react with your skin to produce vitamin D. As we said, it’s a complex topic. 


Get vitamin D from food 

Some foods can help us top up our intake of Vitamin D. They are not as effective at delivering the vitamin as some careful and consistent sunbathing but they can help. Even if you love the foods listed below and eat them several times a week, they are unlikely to provide sufficient Vit D without complementary sources. 

Food sources for vitamin D3 

Cod liver oil 

Oily fish e.g. salmon, tuna, mackerel, herring, sardines (tinned or fresh) 

Egg yolks 

Red meat 

Fortified breakfast cereals 

Fortified fat spreads 



Do I need a vitamin D supplement? 

As stated above, only a blood test can confirm if your vitamin D levels are below that required for optimum health. But many of us will recognise that we have more in common with Profile 2 in the table above than Profile 1. If that’s you, chances are your vitamin D levels could do with a top-up with food, a supplement, or perhaps both. 

And you are not alone. Following a study by the Department of Health and Social Care, the NHS now recommends vitamin D supplements for everyone5 aged 1 year and above, including pregnant and breastfeeding mums, especially during the winter months. (Babies often get what they need from infant formula milk.) 

Some experts believe that supplements are a safer way to access vitamin D3 due to the dangers associated with UBV rays6 

A good multi-vitamin complex may provide you with the vitamin D that you need. Higher-strength supplements may be required by those who simply cannot or choose not to get out into the sunlight very often or who do not eat vitamin-rich foods 

As previously stated, age, skin tone, lifestyle and body mass can all impact on how the body makes and uses vitamin D, as can medicines. If you take prescription medicines, please consult your doctor before taking vitamin D supplements 

Can I take too much? 

Vitamin D’s ability to enable the absorption of calcium, combined with its fat-soluble status, means that it is possible to get too much vitamin D. The consequence is a build up of calcium that, in extreme cases, can cause serious issues in the blood vessels and heart.  

However, this is a rare condition that is likely to be caused by long-term exposure to very high levels of vitamin D. Numerous studies7 continue to add to the debate about optimum levels of vitamin D supplementation 

The checklist:

  • Enjoy the sunshine when you can and stay safe – UVB rays are powerful 
  • Eat a varied diet that contains foods rich in vitamin D 
  • If you’re concerned about your vit D levels, speak to your doctor about a blood test 
  • If you take prescription medication, always consult your doctor before taking vitamin D 
  • Find a supplement that suits your needs and do not exceed the recommended dose 

Shop Vitamin D here. 



References for this guest blog article: 

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