can b12 injections cause itchy skin Common & Rare Side Effects of Vitamin Vitamin B12 deficiency: Symptoms include

Regular screening may be done if you have risk factors or symptoms such as fatigue, numbness, or pale skin

Batch: GF-AOD10-B241 Key analytical results include: Assay Content: 11.48 mg Identification Retention Time: 0.986 Identification Spectrum: 995 Purity: 99.7 percent Bacterial Endotoxins: below 0.001 EU per mg Total Aerobic Microbial Count: not detected Total Yeast and Mold Count: not detected Independent heavy metal screening confirmed no detectable levels of arsenic, cadmium, cobalt, lead, nickel, mercury or vanadium

Biomed Res Int

Hepatology 59 , 17611771 (2014)

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I also note that you have potential thyroid issues - lots of cross-over between thyroid/B12 deficiency symptoms - so might not be easy to sort out which symptoms are due to what