B12 deficiency in kids isn’t always obvious—the symptoms can be subtle and easy to miss, but catching it early is important. Here are the main warning signs:​

Feeling tired all the time or lacking energy (even after a good night’s sleep).​
Muscle weakness or trouble with coordination (kids may have difficulty walking, balancing, or controlling their movements).​
Irritability, crankiness, or mood swings.​
Digestive problems like diarrhea, vomiting, constipation, or loss of appetite.
Slow growth or weight loss, and delays in achieving developmental milestones (like sitting up, crawling, talking, or walking).​
Neurological symptoms: tingling or numbness in hands and feet (“pins and needles”), poor concentration, memory problems, trouble paying attention, and learning difficulties.​
Changes in personality, depression, or behavioral problems.​
A swollen or sore tongue (glossitis), sometimes with mouth ulcers, and possibly skin changes like hyperpigmentation or pale/yellow skin.​
Seizures or involuntary movements (in severe cases).​
Anemia (not enough healthy red blood cells), which makes kids pale, short of breath, and easily fatigued.​
Occasionally, B12 deficiency can even be mistaken for autism or developmental delay in kids, as it might affect speech, social skills, motor development, and more.​