B12 Injections: Are they more effective than supplements?

Having low B12 can cause anaemia, fatigue and a whole host of other things that might make you feel very under the weather. In some cases, a long term B12 deficiency can be responsible for permanent neurological and nerve damage. However, because B12 is stored in our livers, it might take a while for these deficiencies to show (Glass, 1959).

Whatever health and wellbeing looks like to you, it’s important to make sure that your body is getting high-quality nutrients in the right quantities regardless of dietary restrictions, lifestyle, or other factors. B12 is no exception. For some people, the best way to achieve this is by using an oral B12 supplement; for others, it's by having regular injections of B12.

This article explores the different kinds of B12 supplementation, why one might be preferable over the other, and if there are any extra benefits or risks depending on that choice. We’ll also look at the different kinds of B12 you find in supplements and injections, so you know what to look out for when you’re choosing the right one for you. 

There are different kinds of B12?

There are four different kinds of B12, some of which are more bioavailable and active than others! This also helps to determine which kind of supplement you’ll find them in. 

Cyanocobalamin: This is a synthetic form of B12, which the body has to convert into the next two forms below before it can be used. Due to its synthetic nature it’s the most cost effective form of B12, making it the one which is most likely to be found in supplements. However, due to its synthetic nature it is also the least bioavailable and active (Hunt, Harrington and Robinson, 2014)

Methylcobalamin: The first of our non-synthetic forms of B12 is methylcobalamin, a naturally occurring co-enzyme. It is the most bioavailable form of B12, and also the most active, working mostly in our brains, nervous system, and liver (Lindstrand, 1964).

Adenosylcobalamin: Another naturally occurring co-enzyme, adenosylcobalamin works with methylcobalamin to cover most of the body’s need for B12. Adensylcobalamin is also vital in the creation and maintenance of the myelin sheath, which protects nerve cells and your brain, which methylcobalamin can’t achieve (Thakkar and Billa, 2014).

Hydroxocobalamin: Hydroxocobalamin is naturally produced by bacteria in the digestive tract when food is broken down and converted into methylcobalamin and adenosylcobalamin. This form of B12 is most often used to treat serious or long term deficiencies. If a supplement contains hydroxocobalamin as the only form of B12, it is most likely to have been prescribed. This form of B12 is the one most commonly found in prescribed injections, although you may find it in other high strength oral supplements. 

What are the factors which affect absorption? 

There are many factors which can affect the way the human body absorbs nutrients, and B12 is no different. Some of these factors are the results of surgeries, genetic factors or chronic conditions which might require higher levels of B12 to ensure that enough is being absorbed by the body. 

We used to be able to B12 in vegetables as it was present in the soil, but agricultural practices have diminished the levels of B12 in our soil to the point where it is almost non-existent. People who eat animal products can still obtain B12 through their diet but it is harder for vegetarians and vegans. It is believed that up to 90% of vegans and vegetarians are deficient in B12 (R, Se and T, 2014), and therefore recommended that they should use supplements to ensure their continued health. 

However, deficiencies don’t only have an effect on vegans and vegetarians. Even people who get their B12 from animal-based products can still have difficulty absorbing B12. This is due to a lack of intrinsic factor. Intrinsic factor is a protein which is vital in the absorption of B12. Unlike a lot of other vitamins which can be absorbed straight into the bloodstream, B12 relies on binding with a protein called intrinsic factor to do this. People who don’t produce enough of this protein are more likely to suffer from B12 deficiencies. (Dali-Youcef and Andrès, 2009)

Other people at risk include those who have had intestinal surgeries, or have chronic conditions which affect the gut, such as Crohn’s disease or celiac disease (Dahele and Ghosh, 2001).

What does an injection do that an oral supplement doesn’t?

Studies have shown that regular oral supplementation is just as effective as having B12 injections (Masucci and Goeree, 2013). Injections are most often given in the forms of hydroxocobalamin or cyanocobalamin at very high doses. They are extremely effective at raising the levels of B12 in our blood quickly, which can help to reverse a deficiency, and then prevent further deficiency over time. 

However, these do have to be prescribed and administered by a healthcare professional, and are more likely to be given to people who have lifelong conditions affecting their ability to absorb B12 or who are at higher risk of consistent deficiency. They are most often considered as a last resort for consistent supplementation if oral methods prove ineffective at staving off deficiency. 

In short, the difference between oral supplementation and injection is that an injection will provide a higher dose of B12 at regular intervals, whilst oral supplements have a lower dosage and can be taken every day. B12 has a very low toxicity, so large amounts are not considered dangerous. If you accidentally take your supplement twice in a day, for example, your body will excrete whatever isn’t used or needed to be stored.

So, can I just use supplements? 

Absolutely! If you’re like me and want to use B12 supplements to prevent deficiency but aren’t in a position where injections are necessary, you can use an oral supplement to great effect! Here are a couple of tips for choosing a great B12 supplement: 

Find a supplement which contains methylcobalamin: as it is a naturally occurring form of B12, it can be absorbed more easily than a synthetic form which is not as easily recognised by the body. 

Find a supplement in liquid form: These are much more easily absorbed by the body and can get to work much faster. However, you’ll also want to make sure that any of these types of supplements do not contain artificial ingredients, and are all natural. 

Find a supplement with a functional dose: Most of the doses in B12 supplements are between 500 and 5,000 micrograms and will give you enough B12. Those getting prescribed injections from their doctor are likely to only need them once every few months at a very high dosage which is not meant to be used weekly or daily. 

Vivo Life’s plant-based liquid B12 supplement ticks all of those boxes! It contains 500mcg per serving of the three most active forms of vitamin B12: Methylcobalamin, Adenosylcobalamin and Hydroxocobalamin. The liquid form helps the active ingredients bypass the digestive system for optimal absorption and maximum efficacy, giving you the B12 your body needs to support a range of physical and psychological functions in the body. 


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Glass, G.B.J. (1959). Deposition and storage of vitamin B12 in the normal and diseased liver. Gastroenterology, [online] 36(2), pp.180–190; discussion 190-192. Available at: https://pubmed.ncbi.nlm.nih.gov/13620030/ [Accessed 16 Aug. 2022].

R, P., Se, L. and T, B. (2014). The Prevalence of Cobalamin Deficiency Among Vegetarians Assessed by Serum Vitamin B12: A Review of Literature. [online] European journal of clinical nutrition. Available at: https://pubmed.ncbi.nlm.nih.gov/24667752/.

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Hunt, A., Harrington, D. and Robinson, S. (2014). Vitamin B12 deficiency. BMJ, [online] 349(sep04 1), pp.g5226–g5226. doi:10.1136/bmj.g5226.

Lindstrand, K. (1964). Isolation of Methylcobalamin from Natural Source Material. Nature, [online] 204(4954), pp.188–189. doi:10.1038/204188a0.

Thakkar, K. and Billa, G. (2014). Treatment of vitamin B12 deficiency–Methylcobalamine? Cyancobalamine? Hydroxocobalamin?—clearing the confusion. European Journal of Clinical Nutrition, 69(1), pp.1–2. doi:10.1038/ejcn.2014.165.