US$ 29.72
vitamin b12 injection for chicken Rooster 6000 20ML Injectable – J.E.J Gamefowl Supplies Vitamin B Complex Fortified Injection is for use as a supplemental source of B complex vitamins for cattle B-15 & B-12 Supplement for
Description
The U in U100 insulin stands for units, and the 100 means that there are 100 units of insulin in every mL of liquid

Others note temporary tiredness during the initial adjustment period

2017 Sep 15;96(6):3849
adults found that people with the highest B12 levels had significantly lower odds of obesity compared to those with the lowest levels

Yes, split dosing is a valid approach, particularly for doses at the higher end of the range (450-500mcg daily)