little bump came up after b12 injection Painful Lumps with Subcutaneous TRT?? | how to get rid of neck lump B12 Injections - Maryland Plastic

Although adverse reactions to intravenous, intramuscular or subcutaneous injection of 0.9% benzyl alcohol are not known to occur in man, experimental studies of small volume parenteral preparations containing 0.9% benzyl alcohol in several species of animals have indicated that an estimated intravenous dose up to 30 mL may be safely given to an adult without toxic effects

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With intramuscular injections of B12, any excess will result in high levels within your blood so you may experience side effects such as headache, dizziness, tiredness, or gastrointestinal issues including nausea, until your body has metabolised any excess through your kidneys enroute to excretion via urine

Benjamin Ma, MD, Professor, Chief, Sports Medicine and Shoulder Service, UCSF Department of Orthopaedic Surgery, San Francisco, CA