Essential facts about Vitamin B12
Vitamin B12, scientifically termed cobalamin, is a vital nutrient obtained primarily from animal products. It can also be added to foods or taken as a supplement. Vitamin B12 has its role in forming red blood cell’s DNA and aids in the development and functioning of brain and nerve cells.

Vitamin B12 is absorbed in two steps:

  1. In the first step, vitamin B12 is separated from the food with the help of gastric acid present in the stomach, after which it binds with the intrinsic factor (a protein secreted in the stomach).
  2. In the next step, vitamin B12, combined with the intrinsic factor, moves further in the gastrointestinal tract and gets finally absorbed in the distal part of the ileum.

Understanding the physiology behind vitamin B12 absorption is essential to comprehend specific causes of vitamin B12 deficiency.

For children and adolescents to function at an optimum level, they need to consume an adequate diet rich in nutrients to meet the functional and development requirements of the growing body. Thus, it is essential to know how much Vitamin B12 should children and adolescents take and the consequences of cobalamin deficiency in the body.

So this article gives the information that everyone should know about vitamin B12 deficiency in children and adolescents, including causes, symptoms, treatment options, and others.

Vitamin B12 deficiency in children and adolescents is not an uncommon entity. Vitamin B12, along with folate deficiencies, is very common among teenagers. Serum B12 level as 229 pmol/L or an MMA level of 0.26 to 0.29 mol/L in children below 19 years shows the deficiency of Vitamin B12.
Do you think your child or adolescent is at risk for developing Vitamin B12 deficiency? Let’s find out!

Here are some critical factors that result in Vitamin B12 deficiency in children and adolescents. So if you or your child fits under one of these headings, you’re probably suffering from Vitamin B12 deficiency. Consult a doctor about the same as soon as possible.

  1. Plant-based diets:
    Children with a vegetarian diet are more likely to suffer from Vitamin B12 deficiency due to the widespread availability of vitamin B12 in animal-based foods instead of plant-based foods. In addition, it is commonly seen in children belonging to lower socioeconomic strata.
  2. B12 deficient pregnant/ breastfeeding mother:
    Children belonging to mothers who follow vegetarian diets are also at risk of developing vitamin B12 deficiency.
  3. Malabsorption/ gastrointestinal diseases:
    Vitamin B12 deficiency can occur due to disorders that impact the release or absorption of Vitamin B12. Crohn’s disease, malabsorption syndromes, and other gastrointestinal disorders are examples of such disorders.
  4. Stomach/ Intestinal surgeries:
    People who have had stomach/intestinal surgery, such as weight loss surgery, which affects the areas mentioned above concerned with Vitamin B12, may develop vitamin B12 insufficiency.
  5. Congenital disorders:
    Transcobalamin-II deficiency or cobalamin R-binder protein deficiency can result in defects in the transportation of Vitamin B12. Furthermore, metabolic disorders that can lead to Vitamin B12 deficiency include:
    1. Adenosylcobalamin deficiency (congenital deficiency of Vitamin B12)
    2. Methylcobalamin deficiency (occurs when the body is unable to process certain amino acids)
    3. Combined adenosylcobalamin and methylcobalamin deficiency

Symptoms of Vitamin B12 (Cobalamin) deficiency in children and adolescents:

  • Fatigue, weakness
  • Loss of appetite
  • Weight loss
  • Stomatitis (redness along the lining of the mouth)
  • Delay in growth
  • Irritability
  • Developmental delays
  • Peripheral neuropathy: tingling and numbness sensations in hands and legs
  • Megaloblastic anemia
  • Pancytopenia
  • Memory disorders

How is Vitamin B12 deficiency diagnosed in children and adolescents?
The CBC, vitamin B12, and folate levels diagnose vitamin B12 deficiency. In addition, a complete blood count (CBC) can be used to detect Megaloblastic anemia.

Deranged blood values solely can’t suggest a Vitamin B12 deficiency simply because it can be easily masked due to various other factors.

That is the reason why the MMA (methylmalonic acid) test is substantially more sensitive than the standard B12 test for diagnosing vitamin B insufficiency. If a vitamin B12 deficiency in children is suspected, but the blood B12 value or symptoms do not indicate it, testing for homocysteine and MMA is advisable. Additional testing is frequently required to determine a reason once a diagnosis is carried out.

How is Vitamin B12 deficiency treated in kids and adolescents?
Vitamin B12 supplements of 1000-2000 mcg are given orally to patients suffering from mild symptoms. In case of severe symptoms, Vitamin B12 1 mg intramuscular (IM) is usually given 1 to 4 times a week until hematologic abnormalities are resolved, after which it is provided once a month. Unfortunately, the resolution of hematologic abnormalities occurs quicker than neurological manifestations. Therefore, unless the pathophysiologic mechanism underlying the shortage is rectified, children and adolescents should continue vitamin B12 medication for the rest of their life as advised by the physician. Also, it is essential to note that because blood B12 levels do not reflect how much B12 is available in the cells, the success of the treatment cannot be determined by serum B12 levels after injections.

Although most patients improve dramatically due to treatment, there may be some long-term neurological impairment. However, the long-term prognosis appears to be connected to the severity and duration of the deficit, emphasizing the importance of early identification and adequate therapy.

Children with metabolic abnormalities and a deficiency of B12 binding proteins require high vitamin B12 and other treatments. Teenagers can follow the adult treatment plan. However, intake of any supplement or medicinal products should only be carried out after taking advice from the physician.

Is it possible to prevent Vitamin B12 deficiency in kids and teenagers?
Yes! You can always prevent Vitamin B12 deficiency from occurring in most cases, although vitamin B12 deficiency in children has always been a significant public health issue.

To determine the micronutrient status, regular screening should be performed. In addition, children and Adolescents should have a well-balanced diet.
Further, to avoid suffering from chronic irreversible neurological manifestations, it is critical to prevent Vitamin B12 deficiency from arising in the first place.
Vitamin B12 deficiency, like many other deficiencies, is preventable in many people. If you’re a devout vegetarian or vegan, you should consume vitamin B12-fortified bread, cereals, and other grains or take a daily supplement. A standard multivitamin has six micrograms, more than enough to cover the average person’s daily needs.


  1. Vitamin B12 [Internet]. [cited 2022 Jan 24]. Accessed at:
  2. Rasmussen SA, Fernhoff PM, Scanlon KS. Vitamin B12 deficiency in children and adolescents. J Pediatr [Internet]. 2001;138(1):10–7. Accessed at:
  3. Louwman MWJ, van Dusseldorp M, van de Vijver FJR, Thomas CMG, Schneede J, Ueland PM, et al. Signs of impaired cognitive function in adolescents with marginal cobalamin status. Am J Clin Nutr [Internet]. 2000;72(3):762–9. Accessed at:
  4. Carmel R. Discussion: Causes of vitamin B12 and folate deficiencies. Food Nutr Bull. 2008;29:S35-S37.
  5. Verma S. Incidence of Vitamin B12 and Folate Deficiency amongst Adolscents [Internet]. [cited 2022 Jan 24]. Accessed at:
  6. Rudloff S, Bührer C, Jochum F, Kauth T, Kersting M, Körner A, et al. Vegetarian diets in childhood and adolescence : Position paper of the nutrition committee, German Society for Paediatric and Adolescent Medicine (DGKJ): Position paper of the nutrition committee, German Society for Paediatric and Adolescent Medicine (DGKJ). Mol Cell Pediatr [Internet]. 2019;6(1):4. Accessed at: