(I) Vitamin B12 deficiency is difficult to diagnose because symptoms can be subtle. (II) In babies and young children, a lack of vitamin B12 usually manifests itself as lethargy or developmental delays.(III) Too little B12 can also disrupt a child's attention span, reduce motivation and hinder learning. (IV) The vitamin B12, which occurs naturally only in animal products, helps maintain nerve and blood cells. (V) In adults, vitamin B12 deficiency signs can range from mild confusion and irritability to more serious problems such as hallucinations, depression, memory loss and paranoia.