Vitamin B12 Deficiencies: Symptoms & Causes

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: A vitamin B12 deficiency can be caused by many different factors including poor diet and underlying health issues. Find out all you need to know.

Vitamin B12 is responsible for carrying out many important tasks within your body. Not only does it actually help to make your DNA and red blood cells (these carry oxygen around your body), but it also contributes to the proper functioning of your nervous system.

Your body doesn’t naturally make B12, you get it from a variety of animal-based foods such as meat, fish, eggs, dairy and by taking supplements. If you have a diet which is lacking in these B12 rich foods, you may develop a vitamin B12 deficiency which in less severe cases, may show no symptoms, but as time goes on, it can lead to a whole host of problems.

Symptoms of vitamin B12 deficiencyVitamin B12

The symptoms of a vitamin B12 deficiency will usually come on quite slowly and over time tend to worsen. Due to this, it’s very common for it be overlooked or misdiagnosed. Some of the usual symptoms include:

  • Fatigue
  • Muscle weakness
  • Swollen, inflamed tongue
  • Cognitive difficulties which may include trouble thinking or reasoning and memory loss
  • Anaemia
  • Walking problems such as staggering or difficulty balancing
  • Numbness or tingling hands, legs or feet
  • Shortness of breath
  • Dizziness
  • Pale or yellow skin
  • Heart palpitations
  • Personality changes

As you can see from the above, a vitamin B12 deficiency can have many different symptoms and it’s very easy for it to be misdiagnosed as something else.

When should you see a doctor?

See a doctor if you’re experiencing any of the above symptoms, it’s very important for your vitamin B12 deficiency to get diagnosed and treated as soon as possible. The damage from some symptoms that arise as a result of it can be irreversible and the longer it’s left without treatment, the more problematic it can be for your long-term health.

Older couple walking together

Who’s most at risk of a vitamin B12 deficiency?

Vitamin B12 deficiencies are fairly common, but there are certain individuals who are more at risk of developing it, these include:

  • Elderly people
  • Vegans or vegetarians with not enough animal-products in their diet
  • People who have had surgery to remove part of their bowel
  • Those with diabetes and taking drugs like metformin
  • People taking long-term antacid drugs for heartburn
  • Individuals with auto immune diseases

Causes of vitamin B12 deficiencies

Typically, vitamin B12 deficiency is caused by an underlying issue which affects your ability to absorb enough into your body, or it may just be that you don’t have enough of it in your diet. Some of the most common causes of vitamin B12 deficiencies in the UK are as follows:

Pernicious anaemia

Pernicious anaemia is an autoimmune condition that affects your stomach and is one of the biggest causes of vitamin B12 deficiency. This condition causes your immune system to attack your stomach’s cells which produce intrinsic factor (a protein that helps to absorb vitamin B12), so your body can’t absorb it. Pernicious anaemia is most common in women around the age of 60, but can also be inherited and is more likely in those suffering from other autoimmune diseases.


Another big cause of vitamin B12 deficiency is a diet lacking in it. As mentioned previously, B12 is found in meat, fish and dairy, which means that vegans not taking supplements can suffer from it. Additionally, those eating a poor diet may develop a deficiency too.

Stomach conditions

Those suffering from a stomach condition and who have had an operation such as a gastrectomy (where part of the stomach is removed), may have more of a risk of developing a vitamin B12 deficiency.

Intestinal conditions

Certain intestinal conditions can put you more at risk, such as Crohn’s disease which causes the digestive system lining to become inflamed and prevents the body from absorbing enough B12. Celiac disease, bacterial growth and parasites can also impact your ability to absorb B12.


Some medications can reduce your ability to absorb vitamin B12. Proton pump inhibitors used to treat indigestion can make vitamin B12 deficiencies worse as they actually inhibit production of stomach acid which is needed to release B12 from your food. H2 blockers and some diabetes medications can also impact this.

How is vitamin B12 deficiency diagnosed?woman drawing blood

Vitamin B12 deficiency will usually be diagnosed through a routine blood test, during which your healthcare professional will check your levels of B12. One of the issues with examining B12 levels is that it only evaluates how much is in your blood in total, but there’s always a proportion of B12 which will be inactive. Although your body can’t use this, the test may say that your body has normal levels, even if the majority of the B12 in your body is inactive.

If pernicious anaemia is thought to be the cause of your vitamin B12 deficiency, your healthcare provider may carry out further blood tests to look for intrinsic factor antibodies and gastric parietal cell antibodies.

Treating vitamin B12 deficiency

If you’re diagnosed with a severe vitamin B12 deficiency, you may need to have injections of either hydroxocobalamin or cyanocobalamin. Injections will usually be every other day until symptoms improve (typically around two weeks) and will need to be administered by either a GP or nurse.

The ongoing treatment will depend on the cause, if it’s found to be diet related, you may be prescribed B12 supplements to take each day which could be for life or just until your diet improves and levels return to normal.

If your vitamin B12 deficiency isn’t diet related, you may need to have an injection of hydroxocobalamin every few months for the rest of your life. Additionally, if you’ve experienced any neurological symptoms, referral to a haematologist for injections every two months may be necessary.

Preventing vitamin B12 deficiency

For diet related vitamin B12 deficiencies, this can be avoided by eating a diet with enough meat, fish, dairy and eggs. If you’re vegan or have a medical condition that prevents you from absorbing enough B12, you should take a multivitamin that contains B12 or look out for other foods which are rich in B vitamins.

If you’re also taking other medication, consult your doctor before taking a vitamin B12 supplement as they’ll be able to tell you how much you need and ensure that it doesn’t affect your other medications.

Want to find out more about B vitamins and what they do? Read our guide, next.




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