Vitamin B12 is an essential nutrient that plays an important role in red blood cell formation, nerve function, and DNA synthesis. A deficiency in this vitamin can cause a variety of symptoms, including:

Fatigue and weakness: Low levels of vitamin B12 can cause fatigue and weakness, as the body is unable to produce enough red blood cells to carry oxygen to the body's tissues.

Numbness or tingling in hands and feet: Nerve damage caused by vitamin B12 deficiency can cause numbness, tingling, or tingling and prickling feeling in hands and feet.

Difficulty walking: Vitamin B12 deficiency can also cause difficulty with balance, coordination, and walking due to nerve damage in the legs.

Pale skin: Low levels of vitamin B12 can cause the skin to appear pale, as the body is unable to produce enough red blood cells.

Mouth ulcers: Vitamin B12 deficiency can cause mouth ulcers, as well as swelling or irritation of the tongue.

Vision problems: Vitamin B12 deficiency can cause blurred or distorted vision, as well as sensitivity to light.

Cognitive impairment: Long-term vitamin B12 deficiency can lead to cognitive impairment, memory loss, and even dementia.