A toxic vitamin B12 overdose could not occur as the body will absorb what it needs from the B12 injected and excrete any excess in the urine
however, if they get worse or continue, you should contact your doctor or a healthcare provider
The lack of vitamin B12 may result from any of the following conditions: Addisonian (pernicious) anemia this condition causes autoantibody formation against parietal cells, which results in a lack of IF essential for absorption of vitamin B12 from the intestine Malabsorption impaired absorption of vitamin B12 Gastrointestinal pathology, dysfunction, or surgery these include atrophic gastritis, celiac disease, small bowel bacterial overgrowth, pancreatic insufficiency, Helicobacter pylori infection, gastric carcinoma, and total or partial gastrectomy Diphyllobothrium latum and related species (the fish tapeworm) infestation these parasites compete with vitamin B12 for intestinal absorption
Stopping them because a follow-up test looks too high would be a mistake, and untreated vitamin B12 deficiency can cause lasting nerve damage
Resist this urge at all costs