The vitamin B complex is a group of several vitamins, including vitamin B-1, also known as thiamin; vitamin B-2, also known as riboflavin; vitamin B-3, also known as niacin; vitamin B-5, also known as pantothenic acid; vitamin B-6, also known as pyridoxal phosphate; vitamin B-7, also known as biotin; vitamin B-9, also known as folate; and vitamin B-12, also known as cobalamin. A deficiency in B complex vitamins can cause several symptoms. If you think you might suffer from a B vitamin deficiency -- or you're part of a group, such as vegans, that face an increased risk of deficiencies -- then consult your doctor.
Many of the B complex vitamins are required for healthy skin. Deficiencies in these vitamins can cause several symptoms involving the skin, such as dermatitis, dry skin, cracks at the corners of the mouth, frequent bruising and wounds that require a long time to heal, the Colorado State University Extension explains.
A deficiency in many of the B complex vitamins can cause symptoms relating to fatigue. Muscle weakness, lack of coordination and wasting away of muscle mass are all possible symptoms. Pain or soreness in the muscles or joints may also result. In certain cases of deficiency, numbness or tingling in the fingers and toes may occur, the U.S. Office of Dietary Supplements reports.
Mental effects, such as confusion, headache, insomnia or irritability, may result from deficiencies in B complex vitamins. An increased sensitivity to light is another possible symptom. Anemia is also a common symptom of vitamin B deficiencies. Gastrointestinal symptoms, such as nausea, vomiting or diarrhea, may also develop, according to the CSU Extension. Folate deficiency is also harmful, especially in expectant mothers, because it can cause severe neurological birth defects.