What are the effects of vitamin B12 supplementation for children less than 12 years of age?

Key messages

• Vitamin B₁₂ supplementation reduces the risk of vitamin B₁₂ deficiency, and probably improves vitamin B₁₂ levels in children less than 12 years of age, compared to placebo (a substance that looks the same as the intervention/treatment but does not contain any active ingredient) (that is, children who did not take vitamin B₁₂ supplements).

• Vitamin B₁₂ supplements, with other micronutrients (important vitamins and minerals the body needs in small amounts to function), may result in little to no difference in vitamin B₁₂ deficiency or total vitamin B₁₂ levels, compared to children who received the same supplements without vitamin B₁₂.

• The impact of vitamin B₁₂ supplements on other health outcomes in children is less clear.

What is vitamin B₁₂?

Vitamin B₁₂ is an important nutrient that helps make red blood cells and keep the body's cells and nerves healthy. Vitamin B₁₂ deficiency is an important public health problem, including in children and in resource-poor settings. Lower vitamin B₁₂ levels in children have been linked to anaemia (lower haemoglobin levels), and poorer growth, development, and cognition (a child's ability to gain knowledge through thought, understanding, and the senses).

What did we want to find out?

We wanted to find out if taking vitamin B₁₂ supplements would improve the nutrition and health of children less than 12 years of age.

What did we do?

We searched for studies that looked at the effects of vitamin B₁₂ compared to placebo (a substance that looks the same as the intervention/treatment but does not contain any active ingredient), no intervention, or the same supplements without vitamin B₁₂. We summarised the results of the studies and our confidence in the evidence, based on information such as how the study was done.

What did we find?

We included 16 studies involving 4083 children less than 12 years of age (2 days to 11 years). Nine studies, including 2391 children, had data that we could analyse. The studies were conducted in 10 countries around the world. In most studies, the outcomes were assessed immediately after the intervention from five weeks to 31 months, with one study assessing outcomes after nine years. Vitamin B₁₂ supplements were provided from 28 days to 31 months in amounts from 0.9 to 150 micrograms a day.

Supplementation with vitamin B₁₂ alone versus placebo

There may be little to no difference in height/length, cognition (for example, attention), or development (for example, motor skill development). Children who received vitamin B₁₂ supplements had less vitamin B₁₂ deficiency, and probably had higher vitamin B₁₂ levels, compared to placebo. There may be little to no difference between groups in anaemia. No studies provided data on any unwanted (adverse) effects.

Vitamin B₁₂ alone versus no intervention

The evidence is very uncertain for height/length. No studies reported data we could analyse for other outcomes.

Vitamin B₁₂ and other micronutrients, compared to supplements with the same supplement without vitamin B₁₂

There may be little to no difference between groups for height/length, cognition (for example, attention), or development (for example, motor skill development). Children who received vitamin B₁₂ supplementation (with other nutrients) may have little to no difference in vitamin B₁₂ deficiency, vitamin B₁₂ levels, anaemia, or any unwanted effects.

What are the limitations of the evidence?

The small number and the size of studies were limitations of this review. Few studies reported on health outcomes, including growth, cognition, development, anaemia, or any adverse effects. The different ages of children, and differences in the amount of vitamin B₁₂ and when the outcomes were measured, are also limitations of this review.

How up to date is this evidence?

The evidence is up to date as of 23 September 2025.