Most people starting semaglutide or tirzepatide are told to "keep track of it," and then left to work out what that means. A photo of the pen box and a vague memory of "Tuesday, I think" is not a log. After six months of dose changes, a paused week for a holiday, and one injection you are genuinely unsure you took, the gaps are what your prescriber notices.

Four fields carry almost all the value.

Date and time. Not just the date. GLP-1 agonists have long half-lives, so an hour here or there does not matter pharmacologically, but the interval between doses does. Writing the time makes a seven-day rhythm visible, and it makes an accidental five-day or nine-day gap obvious instead of invisible.

Dose in milligrams, not "one click." Pen markings differ between products and between strengths of the same product. Recording 0.5 mg rather than "the small one" means the number still makes sense when you switch pens, and it means a titration step is a number you can point at rather than a story you have to reconstruct.

Injection site. Abdomen, thigh, upper arm — rotated. Site rotation is standard advice that almost nobody tracks, and the people who do track it are the ones who notice when a particular site is consistently more sore or more bruised.

One line on how the week went. Nausea, appetite, energy, whether you skipped meals. Not a diary — one line. Side effects on these drugs are strongly tied to titration steps, and a log that pairs a dose increase with the fortnight that followed lets you tell the difference between "this drug does not suit me" and "that step up was too fast."

Two habits make the log survive contact with real life. Record the dose at the moment you inject, not later — later reliably becomes never. And log skipped or delayed doses explicitly, marked as skipped. A missing row is ambiguous; a row that says "skipped, travelling" is data.

What this buys you is a ten-minute appointment that starts from evidence. Instead of "I think it has been going okay," you can say when each step happened, how long you held each dose, and what the fortnight after each increase looked like. That is the difference between a prescriber guessing and a prescriber deciding.

Paper works. A notes app works. If you want something purpose-built with the fields already laid out, I keep mine in GLP-1 Dose Log, a free web app for logging GLP-1 and peptide doses. The tool matters far less than the habit — but the habit is much easier to keep when the form is already the right shape.