It may have nothing to do with the B12 itself
Document daily dose, injection site, and any observed effects to maintain consistency and track tolerance
The secondary endpoints include achievement of 20% weight reduction, relative change in body weight, change in waist circumference, change in HbA1c, change in systolic blood pressure, change in the quality of life (IWQOL-Lite-CT), and change in short-form physical functioning score (SF-36v2)
J Int Soc Sports Nutr 15(1):8 Churchward-Venne TA, Cotie LM, MacDonald MJ, Mitchell CJ, Prior T, Baker SK et al (2014) Citrulline does not enhance blood flow, microvascular circulation, or myofibrillar protein synthesis in elderly men at rest or following exercise
The bursa can't adapt to a sudden jump in load that fast