Deficiency in B12 impacts nerve function, and one of the earliest signs is paresthesia—a feeling of numbness or tingling in the hands, feet, or even tongue. This is caused by damage to nerves through the lack of myelin, a nerve protective sheath. Most individuals downplay this symptom as temporary or attribute it to staying in a strange position for an extended period. If it is not heeded, this may result in irreversible nerve damage.
Others with low B12 levels describe a sudden, electric shock-type pain that courses through their body, often in their legs or back. This is caused by nerve damage and can become chronic if not treated.
