Vitamin B12 is a water-soluble nutrient, which means it has an exceptionally high safety profile
[1] In moderate deficiencies, feeling tired, feeling faint, mouth ulcers, rapid breathing, upset stomach, pallor, hair loss, decreased ability to think and joint pain and the beginning of neurological symptoms, including abnormal sensations such as, numbness and tingling, and tinnitus may occur
However, for a more sustained and significant improvement in chronic fatigue, it often takes several weeks or even a couple of months of regular injections for the body to fully restore its B12 stores and for symptoms to noticeably subside
The American Association of Clinical Endocrinologists recommends that weight-management pharmacotherapy in adolescents be managed or co-managed by a clinician with specific pediatric endocrinology or adolescent medicine expertise [22]