It works to stimulate the immune system, boost appetite, and support healthy development in both adult cats and kittens especially during periods of recovery, growth, or stress.*
I know there are quite a few variables with oral bioavailability, but assuming taken fasted,
Those Looking for Enhanced Wellness : Some people without a clinical B12 deficiency choose B12 injections for an energy boost or to improve their metabolism, though this use is less medically established
Administration Instructions Intramuscular Injection Instructions Subcutaneous Injection Instructions 503A vs 503B 503A pharmacies compound products for specific patients whose prescriptions are sent by their healthcare provider
Since Vitamin B12 is mostly taken in with animal products such as meats, shellfish, dairy and eggs, people who abstain from animal based proteins are more commonly afflicted