One of the most common symptoms of vitamin B12 deficiency is unusual tiredness. This is not just normal tiredness after a long day. It may feel like your body has no energy, even after rest.
You may feel weak, heavy, sleepy, or unable to do normal daily activities. This can happen because low B12 may reduce healthy red blood cell production, which can affect oxygen delivery.
Mayo Clinic lists fatigue and muscle weakness among symptoms that can happen with very low vitamin B12 levels.
2. Pale Skin or Feeling Lightheaded
Because vitamin B12 helps make healthy red blood cells, deficiency can lead to anemia. Anemia may make a person look pale or feel lightheaded, dizzy, weak, or short of breath.
Some people also notice a fast heartbeat or feel unusually tired during mild activity. These symptoms can also come from low iron, heart problems, dehydration, thyroid disease, or other causes, so blood testing is important.
If you feel faint, short of breath, or unusually weak, do not assume it is just aging or stress.
3. Tingling, Pins and Needles, or Numbness
