What do trough, peak and mid-interval mean?
They are three points on the curve your testosterone follows between doses. The peak is the highest level, reached soon after a dose. The trough is the lowest, just before the next dose. Mid-interval is the halfway point between them.
Every form of testosterone draws its own curve. The Endocrine Society guideline describes levels after testosterone cypionate or enanthate injections rising into the supraphysiological range and then declining gradually, and pellets peaking around one month after insertion before holding in range for three to six months. A single number only means something once you know where on that curve it was taken.
When should you draw labs for each form?
The answer depends on how you take testosterone.
| Form | When to draw | Where the rule comes from |
|---|---|---|
| Weekly injections (cypionate or enanthate) | Midway between injections, around day 3 or 4 | Endocrine Society |
| Twice-weekly injections | Midway between doses, with the day and time of the last shot recorded | The same midway principle |
| Pellets | At the end of the dosing interval, before the next insertion; first check 2 to 4 weeks after the first implant | Endocrine Society and AUA |
| Oral Kyzatrex | 3 to 5 hours after the morning capsule, taken with food, 7 days after starting or any dose change | Kyzatrex label |
For injections, the Endocrine Society adjusts the dose or frequency if the mid-interval level is above 600 or below 350 ng/dL. The AUA guideline adds that the first check should come no earlier than three to four injection cycles, and notes that a mid-cycle draw cannot define the peak and trough by itself. That is why some providers add a trough check when symptoms fade toward the end of the week.
For Kyzatrex, the label sets a no-change band of 460 to 971 ng/dL on that 3 to 5 hour draw. The capsule’s curve repeats twice a day, so the timing is measured in hours rather than days.
How do mistimed draws lead to wrong dose changes?
A draw taken at the wrong point can push a dose in the wrong direction. Here is how each common error plays out.
- Drawn the day after a weekly injection. You are close to the peak, the result reads above range, and the dose is cut. A week later, the old symptoms are back.
- Drawn the morning your next shot is due. You are at the trough, the result reads low, and the dose is raised. Your peaks climb higher, and your hematocrit may follow.
- Kyzatrex drawn late in the afternoon. Many hours after the morning capsule, the level reads low and suggests an increase that a label-timed draw would not have supported.
- Pellets checked too soon. A draw in the first weeks catches the early high, while a draw near the end shows whether the interval is too long.
When a result does not match how you feel, the first question is always when the blood was drawn.
Why does the first check wait a few weeks?
Testosterone needs time to settle into a repeating pattern after you start or change a dose. The Depo-Testosterone label gives the half-life of injected testosterone cypionate as about eight days, so each weekly dose overlaps the last and levels build over several weeks. A level drawn earlier comes from a curve that is still climbing, which is why the AUA waits three to four cycles.
What should you tell the lab and your provider?
Accurate timing only helps if it is written down. On the day of your draw:
- Note the date and time of your last dose, or the date your pellets were inserted.
- For Kyzatrex, note when you took the morning capsule and that you took it with food.
- Keep the same timing for every future draw so results can be compared.
- Do not skip, delay or double a dose to time a test.
If you are deciding between injection schedules, our page on weekly or twice-weekly injections compares the two. For a result that came back above range, see testosterone too high on TRT.
How Ultimate Male times your follow-up draws
Before each follow-up, your provider tells you which point in your cycle the draw should hit, based on whether you are on testosterone injections, testosterone pellets or oral Kyzatrex. Draws are done on site in San Gabriel and Downey, and your dose timing is recorded next to the result.
Only a correctly timed result leads to a change in your testosterone therapy plan. If you are on TRT elsewhere and your numbers keep swinging, the free 10-minute call is a good way to check whether timing is the reason.
