why do i get b12 injections The Advantages of Versus Oral Supplements: Shawn Veiseh, M.D.: Family Medicine Vitamin B12

The pattern below reflects averages from clinical data and real-world observations for someone on a standard dose escalation to 10 mg or 15 mg

Because IM injections send B12 directly into muscle, the vitamin peaks in blood within about an hour, ensuring tissues get what they need

You should contact your GP or NHS 111 if you experience: Persistent diarrhoea lasting more than 7 days in otherwise healthy adults Blood or mucus in stools , which may indicate inflammatory bowel disease or infection Severe abdominal pain or cramping that is worsening or different from previous digestive symptoms Unexplained weight loss alongside bowel changes Signs of allergic reaction , including rash, itching, swelling, or difficulty breathing (call 999 or go to A&E for severe reactions) Neurological symptoms such as numbness, tingling, balance problems, or memory difficulties, which may indicate B12 deficiency is not being adequately treated Seek help sooner if you have red flag symptoms, are pregnant, immunosuppressed, elderly, or have significant underlying health conditions

Vitamin B12 is usually found in animal products, including food like meat and fish