side effects of too much b12 injections do have Vitamin B12: Is It Bad for Your Health? – Too Much B12 Symptoms: Overdose

doi: 10.1016/j.lfs.2017.08.006

Most patients notice initial effects within 1-2 weeks for acute injuries, with progressive improvement over 4-8 weeks

Side effects are usually mild and temporary, such as redness or soreness at the injection site, and typically resolve within a few hours to days

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When B12 is low, red blood cells become oversized and inefficient (megaloblastic anemia), and oxygen delivery to follicles drops

Vitamin B12 deficiency can manifest in several different types, each with distinct causes and characteristics: Dietary deficiency occurs when an individual does not consume enough foods containing vitamin B12, which is primarily found in animal products such as meat, fish, dairy, and eggs