These can include dry skin, higher risk of skin infections, and (ironically) hyperpigmentation, i.e., increased skin darkening
But what if the situation called for something a little more advanced, like starting an IV
I've been working on co-factors and as far as I am able to tell, the only one that's low now is serum ferritin and serum iron (supplementing for these, so that's not the problem)
The evidence supports iron (targeting ferritin above 50 ng/mL), zinc (15-30mg daily), vitamin D (2,000-5,000 IU daily), biotin (5,000mcg daily), a B-complex, and adequate protein (1.0-1.6g per kg body weight)
AEs were not addressed (Hillelsohn 2012), reported as not occurring (Payne 2009), or reported as one case of minor bladder perforation treated with an indwelling catheter for one week (Jhang 2013)
For a subcutaneous B12 injection, a finer, shorter needle is used: around 25 to 27 gauge and half to five-eighths of an inch