Temperature logging at home: what is worth the effort

Temperature logging at home: what is worth the effort — setting out what I have, and where I think it stops being reliable.

Practical question with the units stated, because I have seen how quickly these go wrong without them.

I have a 10 mg vial of retatrutide and I am working to a 0.25 mg step. My syringes are U-100 insulin syringes, 0.3 mL barrel.

I can do the arithmetic and I have done it twice, getting the same answer both times, but I would like someone to check the reasoning rather than the number — specifically whether I have thought about the residual volume correctly, and whether the graduation I am landing on is one a person can actually read.

For anyone arriving from a search: the marked solution above is the direct answer, and the replies underneath it add the caveats that make it safe to use.

Worth separating two things that the opening post runs together.

Protecting from light: amber vials or opaque containers reduce light exposure. If you are storing for long periods and light matters, this is worth doing. For short-term prepared solutions, ordinary storage away from direct sunlight is usually adequate.