According to Harvard Health, (6) factors related to a vitamin B12 deficiency include: Limiting animal products in the diet Vitamin B12 is naturally found in meat, poultry, fish, and dairy products, so individuals that don't eat animal products can often become deficient
Environmental Science & Technology, 844: 157162 Li D H, Li W G, Zhang D Y, Zhang K L, Lv L Y, Zhang G L (2023)

Vitamin B12 shot may be prescribed to prevent or treat the following: Pernicious anemia (a condition in which there are low red blood cell counts due to an abnormality in B12 absorption by the intestines) Megaloblastic anemia (a type of anemia in which there are very large red blood cells called megaloblasts) Cognitive disorders, such as dementia (a disorder characterized by problems with memory, problem-solving abilities, language, etc.) Disorders that affect B12 absorption, such as pancreatic diseases, intestinal infections, Crohns disease, and tropical sprue Cardiovascular disease risk (by lowering blood homocysteine levels, which is a compound associated with an increased risk of heart problems) Multiple sclerosis symptoms Bells palsy recovery B12 deficiencies related to: Weight loss Vegan or restrictive diets Surgery to remove the part of the stomach or the ileum (the last part of the small intestine) Energy and endurance What are signs of vitamin B12 deficiency

doi:10.1007/s11154-012-9214-8
Let the vial equilibrate for 1520 minutes at room temperature first