Twelve weeks on one page. Dose, injection site, weight, waist, side effects and notes — with a reconstitution header so the vial maths lives next to the record instead of on a different piece of paper.
Opens the sheet with the print dialog ready — choose "Save as PDF" to keep a copy. Fits one page at A4 or Letter.
Most abandoned logs die the same way: too much detail in week one, nothing by week four. The columns here are the smallest set that still produces something readable months later — each one earns its place.
The header block ties into the vial maths rather than repeating it: work out concentration and units on the reconstitution calculator, then write the result once at the top of the sheet. There is also a lot / batch field — record it. Where a shop's certificate carries the same lot, it is what connects your vial to published lab results later. Not every vial's lot has a certificate behind it, but you cannot check after the fact if you never wrote it down.
Logs are private by default. Publishing is a separate, deliberate choice.