4. Vitamin B12 deficiency.
The body requires a number of vitamins in order to maintain proper functioning. While all of these vitamins are important, B12 is one of the most crucial, as it plays a key role in red blood cell development, as well as DNA.
While B12 is essential, the body does not naturally produce the vitamin; it can only be obtained through diet. If a person is not ingesting enough vitamin B12, he or she can develop a deficiency. A deficiency of vitamin B12 can be comprised of a variety of symptoms, including fatigue, listlessness, mental confusion, and increased heart rate.
A numbing, tingling, painful sensation in the hands and feet is also a key symptom; it is reported to feel like pins and needles. It also causes mouth pain, which is reported to feel like a burning sensation, which can be associated with ulcers throughout the mouth.