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What Does a Vitamin B12 Blood Test Look for and Why is it Useful?

If a doctor or nutritionist has recommended you take a vitamin B12 blood test, you may wonder why? What is the point of such tests? To answer that question, you need to consider several factors.

What is B12?

Vitamin B12 is one of the eight B vitamins: a group of related but distinct nutrients that typically cluster in foods and which serve similar, essential functions in the human body. Some enable the function of enzymes – these are catalysts for vital biological functions in every cell of our bodies. Others are used by the body to create those enzymes. 

Vitamin B12 or ‘cobalamin’ is the most chemically complex of the B vitamins.

Why is B12 important?

Vitamin B12 plays multiple functions within the body. These include:

  • DNA synthesis – ie the production of DNA within the cells of our bodies
  • The metabolism of important nutrients, including essential fatty acids and amino acids
  • Healthy immune system function
  • Red blood cell production within bone marrow
  • Making myelin – a protective insulation around every nerve cell filament

A good B12 intake will make a strong contribution to overall health. It will also reduce your risk of developing anaemia, heart disease, and osteoporosis, as well as age-related conditions like macular degeneration (vision problems) and memory loss. Learn more about vitamin b12 benefits.

What does it mean if your B12 levels are too high or too low?

Low levels of B12 can bring on a variety of unpleasant symptoms, such as:

  • Pins and needles
  • A sore tongue
  • Vision disruption
  • Mouth ulcers
  • Mood disorders – for example, depression or irritability
  • Nerve damage
  • Temporary infertility in women

Vitamin B12 deficiencies may even be a risk factor for dementia. 

Low B12 levels are not common but they can be triggered by a number of factors. These include:

  • Intestinal illnesses – for example, Crohn’s Disease or coeliac disease
  • Pernicious anaemia – a disorder affecting the number of red blood cells
  • Autoimmune disorders – e.g. lupus
  • Medications that affect the digestive system – those for acid reflux for example
  • Following a strict vegan or vegetarian diet without appropriate supplementation via multivitamins or fortified foods
  • Excessive alcohol consumption
  • And last but not least, simply getting older. It becomes harder to properly absorb vitamin B12 as we age

Unusually high levels of B12 can also indicate health complications, such as obesity, liver disease, diabetes, and some forms of cancer.

How can you maintain your B12 levels?

The best way to ensure good levels of vitamin B12 is to optimise your diet. The primary natural sources are eggs, milk, chicken, and red meat – but those pose an obvious problem for vegetarians and vegans.

If you avoid meat and/or animal products but are concerned about your B12 levels, you will need to explore the many supplements available from pharmacists, health food stores, and online vendors. The principal formats are:

  • Multivitamins
  • ‘B complex’ supplements – ie products containing all the B vitamins
  • Specialist B12 supplements

An alternative source of B12 can be found in fortified foods – i.e. food products that have had vitamins and other nutrients added to boost the health of the people who eat them. B12 is a common addition to bread and breakfast cereals.

How to check your B12 levels

If you’re experiencing symptoms that suggest a vitamin B12 deficiency, consulting a GP or registered nutritionist is a sensible thing to do. They’ll most likely refer you for a B12 blood test. But there’s no need to wait. Why not jump the queues and purchase an at-home vitamin b12 test?

Professional laboratory analysis of your sample will provide you with actionable insights, enabling you to adjust your diet if necessary, and seek appropriate treatment for any developing health issues.

Sian Baker

Medically reviewed by Sian Baker, Dip ION mBANT mCNHC – Written by Beth Giddings.

Updated on 1st December 2021