Anaphylactic shock and death have been reported with administration of parenteral vitamin B12 (see WARNINGS)
It is important to realize that the MTHFR status does not determine the type of B12 thats best for you, instead its the status and combination of genes like COMT , MTR , MTRR as well as VDR Taq
Should you start low
As the However, while risks of severe toxicity are low, some side effects are still possible, such as: temporary symptoms, such as itching, swelling, or diarrhea allergic reaction damage from the injection hypokalemia, or low potassium levels infection negative interactions with certain medications, such as: metformin (Fortamet, Glucophage, Riomet) medications to reduce gastric acid, such as proton pump inhibitors or H2 receptor antagonists Always talk with a doctor before using vitamin B12 supplements
This has the benefit of getting your B12 levels boosted immediately, and little to none gets lost