Vitamin B12
Vitamin B12 is a water-soluble vitamin needed for energy, red blood cell formation, nerve health and overall wellbeing. It is naturally found in animal-based foods, which means that people following vegetarian or vegan diets, or those with reduced absorption, may have lower levels.
B12 supplements can be a helpful way to support energy and general health when dietary intake is limited.
What B12 actually is
Vitamin B12 (cobalamin) is a water-soluble vitamin, made by bacteria and found primarily in animal foods. It is essential for nerve function, DNA synthesis, energy production, mood and cognition and red blood cell formation. Methylcobalamin and cyanocobalamin are the different forms often found in supplements that the body converts to the active form.
It is absorbed in the small intestine with the help of intrinsic factor, a protein made in the stomach. Because it relies on several steps for absorption, some people may find it harder to maintain optimal levels.
How people tend to use B12
B12 supplements (often as methylcobalamin or cyanocobalamin tablets or injections) are taken most often by people with diagnosed deficiency, vegans and vegetarians (whose dietary sources are limited), older adults and those with absorption concerns. They are also used by some for energy, mood and cognitive support.
Plant-based eaters and older adults often particularly benefit from reviewing B12 intake.
What the research is showing
B12 deficiency is genuinely associated with cognitive impairment, mood changes, and neurological symptoms, and correction of deficiency is important.
However, in people with adequate B12 levels, supplementation has not consistently improved cognitive function or mood in randomised trials. Higher B12 levels in older adults are associated with slower cognitive decline, suggesting that maintaining adequate status matters, but adding supplemental B12 to already-adequate status doesn't produce the improvements sometimes hoped for.
Studies also show that:
deficiency is more common in vegans, vegetarians and older adults
certain medications may reduce absorption
low stomach acid (common with age or stress) can impact B12 uptake
fortified foods can contribute meaningfully to intake
Testing B12 levels through a GP or private lab can provide useful context when symptoms or dietary patterns suggest reduced intake.
Where supplementation is appropriate
B12 supplementation is most clearly indicated in people with documented deficiency (confirmed by blood tests) or in vegans and vegetarians relying on supplementation or fortified foods for intake. In people over 65, supplemented B12 or fortified foods are often recommended because absorption efficiency declines. The form matters less than addressing the underlying reason B12 is low (absorption issues, dietary restriction, etc.).
Context is critical
B12 deficiency often reflects an absorption problem rather than simple dietary insufficiency. Addressing the root cause (pernicious anaemia, digestive disorders, medications affecting absorption) is more important than choosing the 'best' supplement form. Supplementing without investigating absorption issues can result in persistent deficiency despite taking pills.
B12 supplements are generally safe, but caution is needed if:
you are using high-dose B12 sprays or injections
you have known B12 deficiency - this requires medical guidance
you have very high B12 levels on blood tests
you take multiple fortified products plus supplements
you react to certain forms (cyanocobalamin vs methylcobalamin)
If symptoms are severe or persist despite good intake, it’s important to discuss this with your GP.
Why form choice matters less than absorption
The body converts both methylcobalamin and cyanocobalamin to the active form. Methylcobalamin is often marketed as 'superior', but evidence doesn't clearly support this. The more important factor is whether the supplement is actually being absorbed, which depends on underlying absorption capacity and the delivery method (injection usually ensures absorption better than oral tablets for those with absorption problems).
While B12 plays a central role in energy and mood, supplements aren’t always the first thing to focus on. Before considering B12 supplementation look at whether you are eating regular meals with adequate protein. Check in on your stress levels and how your digestion feels. And what's your iron status like - energy needs both iron and B12.
Food-first B12 support
Vitamin B12 is naturally present in animal foods: meat, fish, eggs, dairy and some fortified plant-based foods. For those eating animal products, dietary B12 intake is usually adequate. For vegans and vegetarians, reliable supplementation or fortified foods are necessary, as dietary sources are insufficient.
For older adults and those with absorption concerns, working with a healthcare provider to address absorption (through injections, prescribed supplements, or treating underlying conditions) is more effective than self-directed supplementation.
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