Here's a window that closes and never reopens: the weeks before your first injection.
The day you start TRT, you lose the ability to measure where you started from. Everything after that is a comparison against a baseline you either captured or didn't. Most men didn't, and they spend the following year trying to reconstruct it from memory, which doesn't work for reasons covered in why memory fails on TRT.
Why "I felt bad before" isn't a baseline
Ask most men what they were like before TRT and you get a single flattened sentence. Tired all the time. No libido. Low mood. That's a summary, not a baseline, and it's a summary written by the version of you that felt bad enough to seek treatment, which means it's skewed toward the worst of it.
A real baseline is a range, not a sentence. Some days before TRT were worse than others. If you don't know what your good pre-TRT days looked like versus your bad ones, you have no way to tell whether TRT moved your whole range up or just happened to land your first few weeks on days that would have been decent anyway. The single-reading problem applies to your starting point just as much as to any point after it.
What to capture, and for how long
Two to four weeks of daily check-ins before your first injection is enough to establish a range. The same daily state measures you'll track afterward: energy, mood, libido, focus, sleep quality, recovery. Rated the same way, so the before and after are actually comparable rather than measured on two different scales.
This is also the moment to get comprehensive baseline labs, not just the total testosterone number that qualified you for treatment. Estradiol, SHBG, free testosterone, hematocrit, and a thyroid panel establish where you started across the whole system. A year from now, when you're trying to work out whether some marker drifted or was always where it is, the baseline panel is the only thing that can answer the question.
Why it matters more than any single week later
Every judgment you make about whether TRT is working is a comparison against your starting point. Feeling good at month three only means something relative to how you felt at month zero. If month zero is a vague memory, the comparison is a guess dressed up as an assessment.
This gets more important, not less, as time passes. A year in, the question is rarely "do I feel good today." It's "am I better than I was, and by how much." That question is unanswerable without a baseline, and answerable with one. Men who captured a pre-TRT range can look back and see the actual distance traveled. Men who didn't are left arguing with their own memory about whether things really improved.
If you've already started
If you're reading this after your first injection, the pristine baseline is gone and there's no getting it back. That's worth being honest about rather than pretending a reconstructed one is as good. But it doesn't make tracking pointless. It makes your current state the new baseline, the floor you measure future changes against.
The principle holds at every stage. The best time to start capturing a baseline was before your first shot. The second best time is today, because every protocol change you make from here forward is a before-and-after comparison, and the "before" only exists if you logged it. Start now and in three months you'll have the baseline your future self needs for the next decision, even if you can't have the one for the decision you already made.