Long-Term Medication Users Medications such as metformin (used for diabetes) and proton pump inhibitors (used for acid reflux) can interfere with B12 absorption when taken long term, making supplementation necessary
Sarafraz-Yazdi, Ehsan, et al
Immunology 2006
Red Flags to Avoid Warning signs include absence of Certificate of Analysis documentation, unclear peptide sequence or synthesis method information, poor storage and shipping conditions, vendors without established reputation or verifiable history, prices significantly below market rates, and websites with poor grammar, missing contact information, or lack of professional presentation
Using Artificial Intelligence to Assess the Teratogenic Risk of Vitamin A Supplements
For a person with a confirmed deficiency, the documented dangers of leaving it untreated generally outweigh the rare, minor risks of the injections themselves