Vitamin B12 (cobalamin) is a water soluble vitamin that is essential for red blood cell production, neurological and nerve function and DNA synthesis.

Your body does not produce its own B12; it must come from food or supplemental sources.

Your ability to absorb B12 naturally declines with age. Certain conditions and diseases may also affect how much B12 you can absorb from food. Those on a plant-based diet or with gastrointestinal concerns are at risk of vitamin B12 deficiency.

Read our guide to vitamin B12 to find out how this vital vitamin supports your health and how to enhance your B12 intake.

What Does B12 Do For You?

B12 enables blood cells to form properly inside your bone marrow. If your body doesn’t make enough blood cells, your organs do not receive the oxygen they need to function properly, putting you at risk of pernicious anaemia [3]. 

Vitamin B12 is essential to a host of functions within your body including:

• Developing your central nervous system (brain and spinal cord)
• Creating red blood cells
• Maintaining neurological function
• Maintaining health of your hair, nails and skin
• Playing a role in serotonin production and may be used in treatment of depression

B12 deficiency is linked to many neurological impairments, some of which are permanent if deficiency is left untreated. 

The best way to maintain your B12 levels is to eat a well-rounded diet that includes animal products. Where nutritional gaps exist, or if you have poor absorption of B12 due to advanced age or other conditions, your doctor may recommend a B12 supplement.

What Food is the Highest in B12?

Vitamin B12 is found naturally in meat, eggs, fish and dairy products. The highest source of B12 can be found in animal organs, particularly livers.

Active B12 is not present in plant foods, so it is often added to help fill nutritional gaps.

Which Foods are B12 Fortified?

• Nutritional Yeast
• Soy or plant-based milk
• Plant-based ‘meat’ products
• Cereals
• Plant-based yoghurt
• Tofu

Not all products have adequate levels of B12 added; be sure to check the product labels. Foods such as mushrooms, spirulina and kimchi do contain low levels of B12, however the amount is inadequate or the form of B12 may not be bioavailable, and further supplementation may be necessary to ensure sufficient intake.

Signs of B12 Deficiency

[1][2]

• Difficulty concentrating
• Headaches, poor memory, confusion
• Fatigue
• Mood disorders
• Pale or yellow skin
• Muscle weakness
• Bluish or grey-brown nails
• Vision loss

Pregnant and breastfeeding mothers who are B12 deficient place their baby at risk of deficiency. Inadequate B12 in developing foetuses and newborns can have a significant effect on brain development.

Do I Need a B12 Supplement?

Vitamin B12 supplements come in tablets, sprays or injections in cases of severe deficiency. Some people may be advised to take a B12 supplement to fill nutritional gaps, including:

• Those on a plant-based diet, vegans, vegetarians
• People over 65 years old
• Pregnant or breastfeeding mothers
• People using proton pump inhibitors
• People taking metformin
• People with Crohn’s or Celiac Disease
• Older people with gastrointestinal concerns
• People who have been infected with tapeworm
  

The level of B12 that is absorbed by the body varies from person to person; it is often recommended to take a dose higher than the daily minimum to counter a B12 deficiency.

Your body stores B12 in your liver to use it when it’s needed. If you have insufficient dietary intake, your body will use these stores. It will take several months to years before you would experience symptoms of B12 deficiency as a result of your diet [2]. 

What is the Recommended Daily Intake of B12?

People aged 14 years and over should consume at least 2.4mcg of vitamin B12 daily [1]. This amount increases for pregnant and breastfeeding mothers to ensure their baby does not have B12 deficiency.

How to Take B12 Supplements

The most commonly used forms of B12 in supplements are methylcobalamin and cyanocobalamin. Methylcobalamin is the active form of B12, whereas cyanocobalamin must be converted by your body. Both forms are considered equally as effective for most people, though certain conditions may determine which form of B12 is best for you [1]. 

Many B12 supplements are taken sublingually, placed under the tongue. This is because B12 binds to, and is activated by, your mucous membranes.

Supplements may include a high amount of B12, 1000 mcg or more: but your body will absorb the amount it needs and expel the remainder through your urine. 

Best B12 Supplements

Side Effects, Precautions and Interactions

There is no established limit to vitamin B12 intake, as your body will absorb what it needs and expel the rest through your urine.

There have been reports of people experiencing acne, rosacea, and heart palpitations after taking high supplemental doses of B12, though these were mostly limited to people who had B12 injections [2].

B12 supplements could interfere with medications to treat acid reflux and medications for prediabetes/diabetes including Metformin [1].

Summary

B12 is an essential vitamin that supports neurological function, red blood cell and DNA production. It is found in animal products, some fortified foods and in supplements.

Those with certain medical conditions or who are over 65 years may have an impaired ability to absorb B12. People on plant-based or vegan diets may have inadequate B12 intake and require supplementation.

Speak to your healthcare professional to determine if you have a vitamin B12 deficiency and to determine if supplementation is right for you.

References

[1] Medical News Today, 2020. Best Vitamin B12 Foods: Supplements and RDA. https://www.medicalnewstoday.com/articles/vitamin-b12-foods#intake

[2] WebMD, 2023 . Vitamin B12 Deficiency: Causes, Symptoms and Treatment. https://www.webmd.com/diet/vitamin-b12-deficiency-symptoms-causes

[3] Mayo Clinic, 2024. Vitamin B-12. https://www.mayoclinic.org/drugs-supplements-vitamin-b12/art-20363663