vitamin b12 tablets or injections are as effective as Sublingual vs. B12 Injections: Which Option Is Right for You? – WhyNotNatural Oral vs. Intramuscular Do You Need a Prescription

Wang H, Li L, Qin LL et al (2018) Oral vitamin B12 versus intramuscular vitamin B12 for vitamin B12 deficiency

doi: 10.1210/jc.2015-1732

Individuals with Digestive Issues: Conditions like Crohns disease, celiac disease, and gastric surgeries can hinder B12 absorption

Depending on what is in the injections you receive, you could experience the following: Allergic reaction Anxiety Constipation Diarrhea Fatigue Headache Increased heart rate Insomnia Nausea Vomiting It is of note that anxiety, an increased heart rate, and insomnia typically occur only after receiving injections that contain medications like phentermine