In some cases, blood clots have occurred (again, this is typically with a very high dosage, and it is possibly a complication of other medical conditions, or other medications which interact adversely with the B12)
Whether considering a B12 injection or already receiving it, this post will provide valuable information to help you make informed decisions about your health and wellness
JAK Inhibitors in Rheumatoid Arthritis: An Evidence-Based Review on the Emerging Clinical Data
Potential Relevance of Bioactive Peptides in Sports Nutrition. Nutrients, 13(11), 3997
If your provider only said "25 units" without specifying concentration, call them back
(PubMed) Mills JL, Scott JM, Kirke PN, et al