5. Fast heart rate
A fast heart rate may be a symptom of vitamin B12 deficiency.
The heart may start to beat faster to make up for the reduced number of red blood cells in the body.
6. Shortness of breath
Anemia that results from vitamin B12 deficiency may cause a person to feel short of breath, because of a lack of red blood cells and a fast heart beat.
7. Mouth pain
Deficiency in vitamin B12 may cause a swollen, smooth, red tongue, mouth ulcers, or a burning sensation in the mouth.
This is due to a reduction in red blood cell production, which results in less oxygen reaching the tongue.
8. Problems thinking or reasoning
Vitamin B12 deficiency may cause difficulty in thinking or reasoning, and memory loss, as a result of less oxygen reaching the brain.