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Is a vitamin B12 deficiency affecting your health?

With an estimated 6 million people in the UK experiencing a vitamin B12 deficiency, it’s surprising how few people are aware of its impacts.

Vitamins are essential to our body’s natural function, and since we can’t create most vitamins ourselves, we must absorb them through external sources such as diet and supplements. Vitamins divide into two types: fat-soluble and water-soluble. Fat-soluble vitamins, such as vitamins A, D, E and K, are commonly found in oily foods. They are stored in the fatty tissue in your body as well as the liver which your body can draw upon if there are short term gaps in your diet. Water-soluble vitamins are transported in the blood and excreted through your urine. Most, but not all of the water-soluble vitamins cannot be stored by the body.

You should be able to get all the vitamins you need through a healthy diet, but some groups of people have don’t get all the vitamins they need which can raise the risk of health problems. Here we take a look at vitamin B12 and the effect a deficiency of this micronutrient may have on your body.

What is vitamin B12

Vitamin B12 (also known as cobalamin) is a water-soluble nutrient that is used in many of the body's processes including DNA production, the normal functioning of the nervous system, and cell repair.

Vitamin B12 comes almost entirely from animal products such as meat, fish, milk and eggs. There are few natural plant sources of vitamin B12, although small amounts are found in yeast extracts such as marmite and nutritional yeast. However, increasingly plant-based milks and cereals are fortified with vitamin B12.

Once in the body, vitamin B12 is bound to proteins called transcobalamins; 70% is transported on inactive transcobalamin I (TCI or haptocorrin) and cannot be used by the majority of the body’s cells. The other 30% of vitamin B12 is transported on the active protein transcobalamin II (TCII or holo-transcobalamin) and can be used in cells [1].

The human body stores several years' worth of vitamin B12 in the liver, so can often manage with these reserves if it is not provided with B12 from an external source, however, eventually, these reserves will run out too.

What is vitamin B12 deficiency?

A lack or deficiency of Vitamin B12 occurs when the body isn’t getting the required daily intake, this could be due to a dietary shortfall, problems absorbing the vitamin from the gut, or increased usage of vitamin B12 by the body. The recommended daily amount of vitamin B12 will vary depending on your age. Below is a list of the daily average vitamin B12 micrograms (mcg) needed for each life stage [2]:

Age Recommended amount (mcg)
1 year 0.5
2-3 years 0.5
4-6 years 0.8
7-10 years 1.0
11-14 years 1.2
15-18 years 1.5
19+ years 1.5

Vitamin B12 is used by cells to create DNA, and in the metabolism of fats and proteins. The brain and nerve cells use vitamin B12 to create the insulating coat that allows them to transmit electrical impulses. Vitamin B12 is also needed to allow red blood cells to mature, deficiency causes the body to produce less red blood cells, and those it does make are enlarged, hindering the ability of the blood to carry oxygen.

What are the symptoms of B12 deficiency?

As vitamin B12 is necessary for so many functions in the body, the symptoms of deficiency can be equally varied and affect people in different ways. Symptoms typically include:

  • Fatigue
  • Breathlessness
  • Loss of appetite
  • Stomach issues
  • Weight loss
  • Mouth and tongue ulcers
  • Nerve damage
  • Pins and needles or loss of sensation in fingers and toes
  • Muscle weakness
  • Sight and memory problems
  • Mood changes and depression
  • Palpitations

What causes vitamin B12 deficiency, and who is at risk?

The most common cause of vitamin B12 deficiency is an autoimmune disease called pernicious anaemia. This condition causes the body to produce an antibody that attacks the protein responsible for extracting vitamin B12 from food. Read more about pernicious anaemia here.

After being digested, B12 combines with a protein called intrinsic factor in order to be absorbed by the gut into the blood. In pernicious anaemia, the body’s defence system attacks the gastric parietal cells in the stomach wall that make intrinsic factor meaning that it is impossible to absorb vitamin B12 from the food we eat. The cause of pernicious anaemia is unknown, however, is more prevalent in women aged 60 and over, people with a family history of the disease, and those with other autoimmune conditions. You can discover more about autoimmune diseases here.

Others that can be affected by lack of vitamin B12 include people who are on certain drugs and medications (e.g. proton pump inhibitors for acid reflux, metformin for type 2 diabetes and some forms of birth control pill), people who have had surgery to remove part of the stomach and therefore the gastric parietal cells, people who drink excessive alcohol, people with inflammatory bowel conditions like Crohn's or Coeliac disease, as well as the elderly as the body’s ability to absorb vitamin B12 declines with age. It is thought that up to 20% of people over the age of 60 may be affected by vitamin B12 deficiency.

Vitamin B12 deficiency and veganism

Another main cause of vitamin B12 deficiency is a restricted diet - particularly vegan diets as they lack animal products which are the primary sources of B12. Even a healthy, varied vegetarian or vegan diet can result in B12 deficiency, and all vegans are advised to supplement vitamin B12.

If you are vegan or vegetarian, you can consume foods fortified with B12, such as some plant milks, some soy products, some breakfast cereals, dried yeast flakes and marmite. Solely relying on these foods may still make you struggle to meet the recommended daily amount; however, B12 supplements are readily available in most health retailers.

Vitamin B12 deficiency and fertility

Vitamin B12 deficiency can cause temporary problems with fertility, these will usually resolve when the B12 deficiency is treated [4].

Although more research needs to be conducted, there is also a link between B12 and semen quality. Healthy levels of the vitamin are thought to increase the functionality of reproductive organs and decrease inflammation-induced semen impairment [5].

How is vitamin B12 deficiency diagnosed?

If you follow a restrictive diet such as veganism, suffer from thyroid or other autoimmune disorder, or experience symptoms of B12 deficiency, we would recommend that you get tested.

A deficiency is diagnosed through a blood test, and to help you get the answers you need, Medichecks has a range of tests for B12 and Pernicious Anaemia.

As previously explained, only active vitamin B12 can be used in the body, so measuring the total level of B12 could give misleading results and fail to diagnose a deficiency. For example, even if the results showed a normal range of vitamin B12 in the blood, the levels of useful active B12 could still be low. This is why Medichecks measure active B12 so that you can get clear, accurate and useful results.

If you think you might be at risk of a vitamin B12 deficiency, it’s never been easier to get the vitamin B12 tests you need. Our range includes the simplest vitamin B12 test to more advanced checks.

How is it treated?

A vitamin B12 deficiency or Pernicious Anaemia needs to be diagnosed and treated as soon as possible, as some problems caused by the condition can be irreversible [7]. Potential complications caused by prolonged vitamin B12 or folate deficiency include:

  • Damaged nervous system
  • Temporary infertility
  • Heart conditions or heart failure
  • Pregnancy complications and congenital disabilities
  • Anaemia
  • Chronic tiredness & low energy levels
  • Low mood
  • Memory issues/ dementia
  • Increased risk of developing stomach cancer if you have pernicious anaemia

Once a blood test has diagnosed a vitamin B12 deficiency, depending on the cause, your doctor will prescribe treatment of either daily supplements, tablets, or injections.

In some cases, including more vitamin B12 in your diet can treat the deficiency and prevent its return. However, if your intake still isn’t high enough, you may need to take daily tablets in-between meals or have regular injections which may need to be continued for the rest of your life.

What can I do now?

If you are concerned about having a B12 deficiency or fall into any of the high-risk categories, Medichecks’ simple Vitamin B12 (Active) Blood Test can help you get the answers you need. Your results are complete with qualified doctors’ advice which you can then take to your GP to discuss which treatment is most suited to you.


[1] O’Leary, F. and Samman, S. (2010) Vitamin B12 in Health and Disease. Nutrients, [online] 2(3), 299–316. Available at: [Accessed 23/07/20].

[2] Government recommendations for energy and nutrients for males and females aged 1 – 18 years and 19+ years. (2016) Public Health England. Available at: [Accessed /07/20].

[3] Jenkins, Richard C., and Anthony P. Weetman. ‘Disease Associations with Autoimmune Thyroid Disease’. Research-article. Mary Ann Liebert, Inc., 9 July 2004. World.
[Accessed 17/08/20].

[4] NHS (2019) Vitamin B12 or folate deficiency anaemia. [online] Available at: [Accessed 24/07/20].

[5] Banihani, S A. (2017) Vitamin B12 and Semen Quality. Biomolecules [online] 7(2): 42. Available at: [Accessed 24/07/20].