Vitamin B12 (cobalamin) is essential for red blood cell formation, neurological function, and DNA synthesis. Deficiency can lead to anemia, nerve damage, and cognitive decline. It is commonly seen in vegetarians, the elderly, individuals with gastrointestinal disorders, and those taking certain medications (like metformin or proton pump inhibitors).

A lack of B12 impairs red blood cell production, reducing oxygen delivery to tissues. This leads to persistent tiredness, muscle weakness, and overall low energy levels, even with sufficient rest.

B12 plays a role in neurotransmitter synthesis, including serotonin and dopamine. Deficiency can contribute to mood disorders, depression, irritability, and increased anxiety. Some studies suggest a link between low B12 levels and an increased risk of psychiatric conditions.

B12 deficiency leads to megaloblastic anemia, causing larger-than-normal red blood cells that are fragile and prone to destruction. This results in a pale complexion and, in some cases, jaundice (yellowish skin and eyes) due to excess bilirubin from red blood cell breakdown.

Glossitis (inflammation of the tongue) appears as redness, swelling, and a smooth texture. Deficiency may also cause mouth ulcers, burning sensations, or a metallic taste, making eating and speaking uncomfortable.

B12 is crucial for myelin sheath formation, which protects nerves. Deficiency leads to nerve damage, causing tingling, numbness, and "pins and needles" sensations, primarily in the hands and feet. If untreated, it may progress to permanent neuropathy.

Severe B12 deficiency can lead to anemia, reducing oxygen supply to the heart. This may trigger palpitations, irregular heartbeats, or shortness of breath, especially during physical exertion.

B12 deficiency is associated with memory problems, brain fog, and difficulty concentrating. In severe cases, it can mimic dementia and increase the risk of neurodegenerative diseases like Alzheimer’s.

Additional symptoms include: