Vitamin B12 levels in children

A recent publication in the British Medical Journal posed the question “Do high vitamin B12 levels in children matter?
Whilst this paper is not available to the general public our valued colleagues in CluB-12 spotted the important points missed in this paper and filed a rapid response. You can read the response submitted by Willemina with Agata’s input here:

Do high vitamin B12 levels in children matter?

The key point of this message is that standard adult vitamin B12 reference ranges are unsuitable for children and people of Black backgrounds, leading to both false alarms regarding “high” levels and, more critically, missed diagnoses of B12 deficiency.

Clinical laboratories must adopt age- and ethnicity-specific reference intervals to prevent severe, permanent neurological damage and developmental delays in children.

Summary of Key Data

The message highlights that B12 levels are naturally higher in children and vary significantly by age. Based on the cited London study (Sobczyńska-Malefora et al.), the corrected reference ranges (in ng/L) should be:

0-1 year-olds: 215-1389
2-5 years-olds: 374-1494
6-9 year-olds: 332-1081
10-13 year-olds 253-871

Critical Implications

Misdiagnosis Risk: Using the adult upper limit (771 ng/L) for a 3-year-old would incorrectly flag a normal level as “high.” Conversely, because the lower limit is also higher in children, a child might be in the “normal” adult range but actually be deficient.

Ethnicity Factors: The letter notes that people of Black backgrounds also have naturally higher lower-limits, meaning standard ranges may overlook anaemia or deficiency in this group.

Clinical Consequences: Undiagnosed deficiency in children is dangerous because B12 is essential for myelin synthesis (protecting nerves) and neurotransmitter metabolism. Missing a diagnosis can lead to:

• Developmental regression.
• Permanent neurological damage.
• Reduced quality of life.

It’s vital that correct information is shared with patients and health care professionals whether that information is in social media, doctor’s surgeries or research papers.