@Bipalossthis is my moment to shine.
as most of you know I switched to slit dosing pretty early on due to side effects. Through split dosing I've been able to increase my overall dose far beyond what was making me horrendously sick as a single dose.
initially I started by doing a 2/3 + 1/3 dose. Now though I find it’s just most consistent to do half and half.
the only particular advantage of 2/3 + 1/3 is is you always want to inject at the same time of day. I do recommend using the medication function in your phone (I assume non iPhones have this too) to give you reminders though.
using a 15mg pen I would say the best options are the below;
Dropping to 10mg
either 2x 20clicks (5mg) 3.5 days apart (e.g. Fri am and Mon pm)
or 1x 24clicks (6mg) and 1x 16clicks (4mg) on a 4 day/3 days pattern.
staying at 12.5mg
either 2x 25clicks (6.25mg) 3.5 days apart
or 1x 30clicks (7.5mg) and 1x20clicks (5mg) on the 4day/3day pattern
you may, once the side effects are under control want to go to 15mg
2 x 30 clicks (7.5mg) every 3.5 days
or 1x40 clicks(10mg) and 1x 20 clicks (5mg) on the 4 day 3 day pattern.
hope this helps!
personally I find it easiest to dose the same dose every time and just have reminders set for the 3.5day split.