The B12 solution is drawn into a sterile syringe
These injections bypass the gastrointestinal tract, making them especially beneficial for those with absorption challenges, such as individuals with pernicious anemia or post-gastrectomy patients
Others, like correction of anemia or nerve symptoms, might take a few weeks of consistent therapy

Chan School of Public Health: "Vitamin B12." Inflammatory Bowel Diseases: "Prevalence of and risk factors for vitamin B(12) deficiency in patients with Crohn's disease," "Vitamin B12 deficiency in inflammatory bowel disease: prevalence, risk factors, evaluation, and management." MedlinePlus: "Cyanocobalamin Injection." National Health Services: "Hydroxocobalamin," "Treatment -Vitamin B12 or folate deficiency anaemia Contents," "Vitamin B12." Nutrition Reviews: "How prevalent is vitamin B(12) deficiency among vegetarians?" Surgery for Obesity and Related Diseases: "Vitamin B12 deficiency in patients undergoing bariatric surgery: preventive strategies and key recommendations." The American Journal of Clinical Nutrition: "How common is vitamin B-12 deficiency?" The American Journal of Gastroenterology: "Vitamin B12 deficiency in untreated celiac disease." Top B12 Injections Who Get Them, How Quickly They Work Related Articles 22 Healthy Foods High in B VitaminsAny deficiency of B vitamins can lead to various health conditions

Those results are in a different category of efficacy compared with B12 or many over-the-counter supplements