Oral B12 looks cheap, but if your body absorbs very little of each pill because of low stomach acid or a gut condition, much of that spending does not translate into results, and you keep buying bottle after bottle
This produces a 5mg/ml concentration that is easier to measure accurately on a standard U-100 insulin syringe , especially at lower starting doses like 2.5mg
Having to stop mid-process to find a syringe or an alcohol wipe is how mistakes happen
ICH Q2(R2) describes analytical-procedure performance characteristics such as specificity or selectivity, accuracy, precision, detection limit, quantitation limit, linearity, range, and robustness, as applicable to the intended use of the procedure