Your clinic emails you to come in for labs. You drive over Wednesday afternoon, two days after your Monday injection. The panel comes back: Total T 1240 ng/dL, E2 62 pg/mL. Your doctor adjusts your protocol down.
But your numbers are wrong. Not the values · the timing. You drew at peak, not at trough. You're looking at the highest your testosterone will be all week. The protocol is fine. The lab draw was the problem.
This is the single most common mistake in TRT optimization, and it's the reason your Reddit forum is full of users insisting their dose is "too high" when it's actually right where it should be.
Trough vs peak: what they actually mean
A compound with a half-life has a curve. Right after injection, levels climb. They peak · for most TRT esters, somewhere between 24 and 72 hours after the shot. Then they fall, slowly, until just before your next dose. That low point is the trough.
- Peak = highest serum level, hours-to-days after injection
- Trough = lowest serum level, just before the next injection
- Steady-state = the consistent peak/trough you settle into after 4–5 half-lives have passed
The classic mistake is drawing at peak and treating the number as your "average." It's not. Your average is somewhere between peak and trough. Your trough is what your body sees most of the time. And · critically · your trough is what determines whether you're symptomatic between doses.
Why trough matters for protocol decisions
Two patterns explain most clinical decisions:
Pattern A: Peak T = 1200, trough T = 400. Average = 800.
Pattern B: Peak T = 900, trough T = 700. Average = 800.
Same average. Wildly different lived experience. Pattern A is the "rollercoaster" · you feel great Monday, crash Friday. Pattern B is dialled in · steady all week.
The protocol fix for Pattern A isn't a lower dose. It's more frequent injections with the same total weekly dose. You're chasing flatter peaks and higher troughs.
But you'll never see Pattern A vs Pattern B in your labs if you only ever draw at peak.
Ester half-lives · the numbers you actually need
Here are the operating half-lives (in days) for the common testosterone esters, as published in the ABIM endocrinology board prep tables and confirmed in the Endocrine Society practice guidelines:
- Propionate: ~0.8 days (19 hours)
- Cypionate: ~8 days (effective)
- Enanthate: ~7 days (effective)
- Undecanoate (Nebido): ~21 days
- Sustanon (mixed): ~14 days effective, peak-skewed
Your trough window is roughly the 48-hour period right before your next scheduled injection.
For someone running cypionate once a week on Monday, the trough window is Sunday morning through Monday morning · draw blood before the injection.
For someone running cypionate twice a week (Mon/Thu), the trough is right before either dose. The convention is to draw Thursday morning, before that day's injection.
For someone running EOD propionate, you're basically always near trough · propionate's short half-life means peaks dissipate within 24 hours.
How Regimio automates this
The trough reminder is one of the killer features I built first because every existing app gets it wrong.
When you add a TRT compound to your stack, Regimio asks for:
- The ester (cypionate, enanthate, propionate, undecanoate, custom)
- Your cadence (once weekly, twice weekly, EOD, custom)
- Your typical injection day(s)
From those three inputs, the app calculates your trough window and schedules a local notification 12–24 hours before your next injection:
"Trough window · draw blood tomorrow morning before your shot."
If you log your shot early · say, you injected Wednesday night instead of Thursday morning · the next trough reminder shifts with it. The schedule is dynamic, not frozen.
The notification is local, not pushed from a server. It fires whether or not you have signal, whether or not the app is open. We test this aggressively because notification reliability is the #1 rage-quit trigger in this category.
How to actually book a trough draw
If your clinic uses Quest or LabCorp, you can usually skip the doctor-handoff for routine TRT panels and book yourself.
The cheap path:
- Order labs through DiscountedLabs, OwnYourLabs, or Marek Health. Total T, free T, SHBG, E2 sensitive, hematocrit, CBC, CMP, lipids · full panel is ~$80–$150.
- Schedule the draw for early morning the day of your next injection. Most lab locations open at 6:30 or 7:00 AM.
- Fast. Some markers (like cortisol and lipids) want fasted draws. Total T isn't sensitive to fasting, but if you're getting them in the same panel, fast.
- Inject after the draw. This is the moment your trough is captured.
If you're working with a doctor, write the timing on the requisition: "Trough draw, request fast morning timing, last injection [date]." Most ordering clinics will honour it.
Why this is in the app, not a blog post
The reason this matters is simple: most TRT users only realize they've been drawing at peak after the protocol adjustment makes their symptoms worse. They titrate down based on bad data. They feel flat. They blame the protocol. They quit.
Regimio's trough-day reminder doesn't just fire a notification. It also logs the draw date as a lab_result.draw_type = 'trough' so when you import your panel results, the app knows which point on the curve you sampled. That's the foundation for honest protocol decisions.
You can't trust your data until you trust your timing. Trough day is the timing. Regimio is what makes the timing automatic.
Try it in the private beta. If you want a deeper read on the math, reconstitution math without rounding is next.