What are vitamins and should I supplement?

Supplements can be a good way of adding extra nutrients into our diet. This vitamin guide contains everything you need to know about the 13 essential vitamins, and whether you need to take a supplement.

We discuss:

• What are vitamins?
• How many types of vitamins are there?
• Vitamin D
• B vitamins
• Vitamin A
• Vitamin E
• Vitamin K
• Vitamin C
• Should I supplement vitamins?

What are vitamins?
 

Vitamins are important micronutrients found in food that keep our body working properly. If you become deficient in a vitamin, you might notice unwanted symptoms, such as feeling overly tired or unable to concentrate.

Vitamins can be categorised into fat-soluble and water-soluble, depending on where in the body they are stored.

Fat-soluble vitamins are stored in our body’s fat, where they can remain up to six months before being used. This means we don’t need to eat them every day, and can actually become toxic when taken at high doses.

On the other hand, water soluble vitamin are excreted in our urine, and need to be taken or eaten regularly to avoid becoming deficient.

How many vitamins are there?
 

There are currently 13 recognised vitamins. Some vitamins, such as vitamin A or E refer to groups of compounds known as vitamers - which are slightly different in structure, but all have the same biological effect.

Fat-soluble vitamins:  

• Vitamin A
• Vitamin D
• Vitamin E
• Vitamin K

Water-soluble vitamins:

• B vitamins (B1, B2, B3, B5, B6, B7, B9, B12)
• Vitamin C

Let’s take a look at each one, going in order of occurrence of deficiency in the UK.

Vitamin D
 

First up, it’s the most common vitamin deficiency in the UK: vitamin D.

Fat-soluble vitamin D is produced in our skin in response to sunlight. So it’s little wonder it’s the most common deficiency in the UK.

We need vitamin D to keep our muscles and bones healthy, and it’s linked to supporting our mood too. You can get a small amount of vitamin D from oily fish and eggs, but sunlight is the most efficient way to boost your levels.

There are a few symptoms of vitamin D deficiency. But since they aren’t exclusive to vitamin D deficiency, a blood test can be the best way to figure out if your levels are low.

You can also check your vitamin D levels from the comfort of your own home with our Vitamin D (25 OH) Blood Test.  

Should I supplement vitamin D?

The NHS recommends everyone who lives in the UK supplement with vitamin D in winter, and some people should consider supplementing year-round.

If you’re not sure which vitamin D supplement you should take, we’ve written a handy guide to help you choose.

B vitamins
 

Altogether there are eight B vitamins, each with its own purpose and role within the body.  They are all available through a healthy balanced diet and are water-soluble.

B vitamins are crucial for: 

• Cell metabolism  
• Normal functioning of the central nervous system  
• Formation of red blood cells 
• Converting food into fuel  
• Metabolising fats and proteins

Should I take vitamin B supplements?

Two of the most common B-vitamin deficiencies are vitamin B9 (folic acid) and vitamin B12.

A B12 deficiency is more common in people who have an autoimmune disease which prevents the absorption of nutrients (such as coeliac disease, or Crohn’s disease). But can also be found in people who restrict dairy in their diet (such as vegans). 

During pregnancy, your body will need more B9 as it is vital for the development of the baby’s nervous system and can reduce the risk of the baby developing spina bifida. 

Therefore, when trying to conceive and during the first 12 weeks of pregnancy, you should supplement the recommended amount of folic acid. 

Vitamin A
 

Vitamin A is a fat-soluble antioxidant. It helps to fight inflammation, strengthens our immune system and maintains our vision.

There are a few forms of vitamin A, but the main ones are:

• Beta-carotene
• Vitamin A₁ (a.k.a. retinol)

Beta-carotene is the pigment that gives foods such as carrots, mangos and pumpkins their orangey colour. Once you eat it, the body converts it to retinol.

Retinol, which you may have heard of as a skincare ingredient, is found in animal-based foods.

Fun fact: Consuming too much beta-carotene can turn your skin orange.

Do I need vitamin A supplements?

Though less common in adults, a vitamin A deficiency is possible.  

Symptoms of vitamin A deficiency include weight loss, dry skin, respiratory infections, and vision loss.

The NHS recommends for vitamin A:

• 7mg per day for men  
• 6mg per day for women 

Because vitamin A is a fat-soluble vitamin, toxicity from too many vitamin A supplements is possible. Check your levels either with your GP or a Vitamin A (Retinol) Blood Test before you start supplements.

Vitamin E
 

Vitamin E is a group of fat-soluble antioxidants, working to prevent cell damage from things like cigarette smoke or pollution. It also helps your body use vitamin K properly.

You can get vitamin E from plant-based sources such as nuts, seeds and wholegrains, and also from eggs.

Should I supplement vitamin E?

You don’t need much vitamin E each day, and a deficiency is usually down to dietary or digestive conditions.

Symptoms of a vitamin E deficiency include:

• Muscle weakness 
• Deterioration of muscle mass 
• Vision problems  
• Anaemia  

It’s thought that vitamin E supplementation when you don’t have a deficiency has no positive effects, and potentially some negative effects.

You can check your vitamin E levels with a Vitamin E (Alpha Tocopherol) Blood Test.

 

Vitamin K
 

Vitamin K refers to a group of fat-soluble vitamins.

They play a role in regulating blood calcium levels and bone metabolism. In the liver, vitamin K is needed to produce four clotting factors that are necessary for blood to properly clot.  

You can get vitamin K from broccoli and spinach, vegetable oils, and some fortified breakfast cereals. There’s also some vitamin K in chicken and dairy products.

Any vitamin K in the body that is not needed immediately is stored in the liver for future use. And the healthy bacteria that live in the digestive system can produce vitamin K. 

Should I supplement with vitamin K?

Vitamin K deficiencies are most common in newborns (occurring during the first few weeks of infancy) due to low clotting factor levels, and low vitamin K content of breast milk. Because of this, a dose of vitamin K is given to newborns as standard in the UK as a deficiency can cause problematic blood clotting and increased bleeding.  

In adults, vitamin K deficiencies are rare but can lead to problematic blood clotting and increased bleeding.  

Symptoms of a vitamin K deficiency include [5]: 

• Bleeding from the nose and gums 
• Heavy periods 
• Slow wound healing  
• Easy bruising 

Check with your GP before starting vitamin K supplements, or check your levels with a Vitamin K (Nutritional) Blood Test.

Vitamin C
 

Last but not least, is vitamin C. Also known as ascorbic acid, it’s another powerful antioxidant. It also has roles in the skin, helping the body synthesis collagen.

Vitamin C also helps to strengthen the immune system and aid the absorption in the body. As it is a water-soluble vitamin, the body is unable to make or store vitamin C, so we get it through the foods we eat.  

The best sources of vitamin C are fruits such as strawberries, tomatoes and oranges, and vegetables such as broccoli and peppers.

Should I supplement vitamin C?

Not getting enough vitamin C can lead to a deficiency that can cause a range of symptoms in the body. 

Symptoms of a vitamin C deficiency include:

• Inflammation 
• Bleeding of the gums 
• Dry hair and skin 
• Slow wound healing  

A long-term insufficiency of vitamin C can lead to a condition called scurvy. In modern-day society, scurvy is rare (historically, it was common in men at sea), but people with gastrointestinal conditions are more susceptible.  

You’ll often find vitamin C in iron supplements as the vitamin C aids iron absorption.

Should I supplement any vitamins?

People take dietary supplements for all kinds of reasons, whether to improve health, boost vitality, limit the signs of ageing, or try and reduce the risk of chronic disease. 

Most people do not need to take supplements as they get all the vitamins and minerals, they need through eating a healthy, balanced diet. If this is something you struggle with, then supplements may be a good idea, although you should check with your doctor first.

There is no straightforward yes or no answer to the question of whether you should be taking supplements - everyone’s circumstances are unique.  

The need for supplementation depends on the levels of vitamins and minerals in your body. Remember, it is also important not to over supplement as this can have negative health effects. 

To make it simple to establish and monitor your levels, we have created our Nutrition Blood Test, to help you see whether you are getting the nutrients you need from your diet and if you could benefit from taking a dietary supplement.

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References 

1. National Institute on Aging. 2022. Vitamins and Minerals for Older Adults. [online] [Accessed 23 October 2025]. 
2. NHS, Vitamin E. [online] [Accessed 20 October 2025]
3. nhs.uk. 2024. Vitamins and minerals - Vitamin A. [online] [Accessed 23 October 2025]. 
4. Girolami, A., Ferrari, S., Cosi, E., Santarossa, C. and Randi, M., 2018. Vitamin K-Dependent Coagulation Factors That May be Responsible for Both Bleeding and Thrombosis (FII, FVII, and FIX). Clinical and Applied Thrombosis/Hemostasis, 24(9_suppl), pp.42S-47S. 
5. Labtestsonline.org.uk. 2022. Vitamin K Deficiency. [online] [Accessed 23 October 2025]. 
6. Harding, D., 2022. Vitamin C Deficiency. [online] Patient info. [Accessed 20 October 2025].
7. nhs.uk. 2022. Vitamin B12 or folate deficiency anaemia - Symptoms. [online] [Accessed 20 October 2025]. 
8. nhs.uk. 2025. Vitamins and minerals.[online] [Accessed 23 October 2025].