long term side effects of b12 injections Vitamin B12: Overdose and Can Vitamin B12 Deficiency Indicate

Dizziness: Rare, but reported occasionally, especially if injecting without eating for extended periods afterward

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Stella Fulman

Rare but serious: severe allergic reaction with trouble breathing, chest tightness, or swelling of face and throatseek emergency help right away

This prevents bacteria from being injected into the skin, which could cause an infection, Connor says

True B12 toxicity symptoms are rare but may include skin reactions, mild gastrointestinal disturbances, and headaches, particularly with injections