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Vitamin B12 absorption

How do you know if your body can absorb vitamin B12? What tests are best to show if absorption is good? Where is the best place to have the tests?

21 August 2019

This content was last reviewed in August 2019 by Nikki Porges, a registered nurse in our Health at Hand team.

Generally speaking a healthy body will have no trouble absorbing vitamin B12. However, if someone does have poor or reduced absorption of vitamin B12, they will start to develop symptoms of vitamin B12 deficiency, that indicate there may be a problem.

Before we look at specific symptoms, it can be helpful to know why we need vitamin B12 and the role it plays in keeping our bodies healthy.

Why do we need vitamin B12?

Vitamin B12 is crucial in helping to keep our nerves and brain function healthy. It is also involved in the formation of healthy red blood cells and helps to both regulate and create DNA.

What happens when we don't have enough vitamin B12 in our bodies?

Vitamin B12 deficiency is a type of anaemia where the body is unable to produce healthy red blood cells. Instead the types of cells produced tend to be large and fragile and these are less able to pass into the circulation and can easily break down. This reduction in red blood cells in the circulation then causes symptoms of anaemia such as weakness, breathlessness and palpitations for example. This particular form of anaemia is known as Megaloblastic Anaemia referring to the abnormal size and shape of the red blood cells being produced.

Causes of vitamin B12 deficiency

Causes of this type of deficiency can be linked to:

  • Poor nutritional status, as a result of malabsorption of nutrients in the stomach or intestine e.g. due to known IBS/Crohn’s Disease
  • Choice of diet e.g. vegan/vegetarian
  • Medications, such as those used to minimise stomach acid production.
  • Other medical illnesses, such as those involving the renal or hepatic systems.

Symptoms of vitamin B12 deficiency

When someone does not have sufficient B12 in their bodies the types of symptoms that can commonly develop are:

  • pins and needles in the body, typically upper limbs and hands but can also happen in the lower limbs and feet as well
  • pale or jaundiced skin
  • mouth ulcers
  • a red sore and smooth tongue
  • changes in movement and gait
  • muscle weakness
  • vision problems
  • changes in mood, e.g. depression, irritability
  • problems with mental agility, e.g. memory changes and a general shift in the way someone thinks, feels and behaves.

As you can see the list is quite extensive and it’s important to remember that people will not usually experience all of the symptoms, very often it is just a few of them.

Diagnosing vitamin B12 deficiency

If you feel that you may be deficient in Vitamin B12 - or are worried that you may not be absorbing it as well as you should - testing for this is very straightforward and can be performed by your GP.

A sample of blood will be taken and sent for analysis to check the level of B12 that is circulating in your blood. Usually they will check the size and number of red blood cells too. 

If a deficiency is found, your doctor should be able to recommend the best course of treatment to correct this for you and may also investigate the reason for the deficiency as well if needed.

You may find the following NHS resources useful:

Vitamin B12 or folate deficiency anaemia

Blood tests

Answered by the Health at Hand team.

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