No adverse effects were noted in clinical trials (ulcerative colitis, phase II) [84,85], and in toxicological studies, a lethal dose (LD1) was not achieved (for review, see [11,12,13,14,24,25])
Minor side effects can include: A bit of tenderness, puffiness, or pink discoloration right around the puncture A brief warm or flushed sensation Mild headache or nausea Reach out to a medical professional right away if you notice: Redness that keeps spreading, heat, or discharge near the site (possible infection) Hives, facial swelling, or difficulty breathing (possible allergic reaction) Persistent numbness or tingling that spreads beyond the site Fever or chills within 48 hours of injection Safe Needle Disposal and Storage A proper FDA-cleared sharps bin is ideal
WARNINGS: Store in cool, dry place
1 2 3 "Vitamin B12, folate, and the methionine remethylation cycle-biochemistry, pathways, and regulation" (PDF)