It is worth noting that there is no established link between standard-dose vitamin B12 supplementation and serious gastrointestinal pathology
When designing experiments, always consult primary literature for the specific model system in use and apply appropriate allometric scaling
But several situations make it especially reasonable
General subcutaneous injection at distant sites like the abdomen can still provide systemic benefits, just potentially with a slower onset for the specific shoulder condition
Bever Yv, Bruggenwirth HT, Wolffenbuttel KP, Dessens AB, Groenenberg IAL, Knapen MFCM, De Baere E, Cools M, van Ravenswaaij-Arts CMA, Sikkema-Raddatz B, van der Claahsen- H, Kempers M, Rinne T, Hersmus R, Looijenga L, Hannema SE (2020) Under-reported aspects of diagnosis and treatment addressed in the Dutch-Flemish guideline for comprehensive diagnostics in disorders/differences of sex development