For a 220-pound (100 kg) starting weight, thats roughly 33 pounds
This page helps with dose planning, vial math, timing, and storage
Published work on intranasal peptide delivery (for insulin analogs, calcitonin, and oxytocin) demonstrates that bioavailability for this size class without enhancers is typically in the low single-digit percent range, though these data are from different peptides with different charge profiles
Veganism, for example, is more common in todays society and with B12 normally being obtained from liver, milk, eggs, fish, oysters and clams a B12 injection is an alternative method of ensuring your body still receives these essential vitamins