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Children need vitamins including B12 to help their brains and bodies develop and grow. 

Not getting enough vitamin B12, which is also called cobalamin, can make children feel weak and tired and slow down their growth and development. If left untreated, this deficiency in B12 can lead to rare but serious concerns including brain damage, nerve damage, and other health issues. When a vitamin deficiency is caught and treated early, most children recover and thrive. 

Here’s what you need to know about vitamin B12, the symptoms that your child is not getting enough, when it’s time to talk to your child’s pediatrician, and how a vitamin B12 deficiency can be treated. 

Why Is B12 Important?

Vitamin B12 helps keep your nervous system and blood cells healthy. It is needed to make red blood cells – which carry oxygen from your lungs to the rest of your body – and DNA, the genetic material in your cells. Vitamin B12 is also important for brain development in babies and young children.

Our bodies do not make B12. Instead, you get it from foods that have B12 or vitamin supplements. 

B12 is found in: 

  • Meat, including red meat and poultry
  • Fish
  • Eggs
  • Dairy products like milk, cheese, and yogurt 
  • Fortified breakfast cereals 
  • Fortified nutritional yeast 

The amount of vitamin B12 children need varies and increases with age. Women who are pregnant or breastfeeding require higher levels of B12, since the vitamin is passed along to their babies. 

How Do Children Become Deficient in B12?

Some children and adults with intestinal and autoimmune disorders, including pernicious anemia, lack proteins in the stomach that help the body absorb vitamin B12. People who have stomach surgery may also have trouble absorbing the vitamin. 

Children who eat little or no dairy or meat – such as those following strict vegan or vegetarian diets – may not get enough of the vitamin from their diet and require a vitamin supplement.

Babies can develop low levels of B12 if their mothers had low vitamin levels during pregnancy. During pregnancy, a fetus collects and stores vitamin B12, which their bodies use for the first few months of life. Therefore, vitamin B12 deficiency may not be spotted until a baby is about 4 months older. 

What Are the Symptoms of B12 Deficiency?

Vitamin B12 deficiency can be hard to spot in children because the symptoms are vague and can be caused by a variety of reasons. 

Signs of vitamin B12 deficiency in children and babies can include: 

  • Fatigue and extreme tiredness or lack of movement
  • Muscle weakness
  • Irritability
  • Stomach issues such as diarrhea, vomiting, or constipation
  • Weight loss
  • Delays in hitting developmental milestones, such as sitting, crawling, walking, talking, etc. 
  • A swollen or inflamed tongue (often known as glossitis of the tongue)

Children can also develop megaloblastic anemia, or very large red blood cells, or low counts of red and white blood cells and platelets, which can be seen or found through medical tests. 

How Can My Doctor Tell If My Child Is Deficient in B12?

Your child’s vitamin B12 levels can be checked through a routine blood test, also known as a complete blood count or CBC, or a B12 serum test. Your child’s pediatrician can order the tests. 

How Is B12 Deficiency Treated? 

Vitamin B12 deficiency is treated by eating more foods with B12 or taking a B12 supplement. There are many brands of B12 supplements in a variety of doses, so it’s important to talk to your child’s doctor to see which is best for their age and needs. 

Doctors can also inject vitamin B12 into your child’s muscles if they are young, have a severe deficiency, or have trouble absorbing the vitamin. 

Most of the problems caused by low B12 go away once a child starts treatment and their vitamin levels rise. While it’s rare, if left untreated, some children with vitamin B12 deficiency can have permanent damage to their brain and nervous system and other health problems. 

Are There Risks to Taking Vitamin B12 Supplements?

You should talk to your doctor before you start taking vitamin B12 supplements because it can interfere with some medications. B12 can interfere with medications for prediabetes and diabetes and medicines to help with digestion problems, like acid reflux. 

When Should I Talk to My Child’s Doctor About a Possible B12 Deficiency? 

If your child follows a strict vegan or vegetarian diet, talk to your pediatrician about checking or monitoring their B12 levels and ask if they should take a supplement.

If your child exhibits symptoms of a vitamin B12 deficiency, bring them in to see their pediatrician. Early treatment can help keep their growth and development on track and help prevent long-term health problems. 

Show Sources

Photo Credit: AzmanL / Getty Images


The Journal of Pediatrics: “Vitamin B12 deficiency in children and adolescents.”

USDA: “Eye on Nutrition: Vitamin B12.”

Harvard T.H. Chan School of Public Health: “Vitamin B12.”

National Institutes of Health: “Vitamin B12: Factsheet for Health Professionals.”

USDA WIC Works Resource System: “Eye on Nutrition: Vitamin B12.”

Children’s Hospital of Philadelphia: “Megaloblastic Anemia.”

CDC: “Vitamin B12.”

Canadian Paediatric Society, Caring for Kids New to Canada: “Vitamin B12 Deficiency.”  

National Institutes of Health: “Vitamin B12.”

Nutrition Reviews: “Vitamin B12 levels in children and adolescents on plant-based diets: a systematic review and meta-analysis.”

American Family Physician: “Vitamin B12 Deficiency: Recognition and Management.”

Mayo Clinic: “Vitamin deficiency anemia.”

Italian Journal of Pediatrics: “Vitamin B12 deficiency as a cause of severe neurological symptoms in breastfed infant – a case report.”