Short answer: Testosterone propionate has a half-life of about 20 hours (Nieschlag E, et al. 1976) and reaches steady state after about 4.2 days of regular dosing. We could not confirm a published time to peak for testosterone propionate, so we do not state one. With the same total per week, Dose Track's model gives a peak-to-trough swing of about 2.03:1 daily and about 4.38:1 every other day.
Relative units: 1 on the scale is one full dose. There is no FDA label dose for this use, so the chart shows the shape of the curve, not an amount. Dashed line: 5 half-lives. Change the amount or schedule in the calculator.
We could not confirm a published time to peak for testosterone propionate, so we do not state one. The chart follows the app: for an oil injection into muscle it counts what is still in the injection depot plus what is in blood, so the modeled total is highest right after each shot and then falls as the depot releases and the body clears it. The curve still needs a rise time, so it uses the app's modeling estimate; treat the shape of the first day or two as approximate.
With regular dosing at a fixed amount and interval, levels climb toward steady state by the same fraction every half-life, whatever the dose. At a half-life of about 20 hours:
| Share of steady state | Half-lives | Time |
|---|---|---|
| 50% | 1 | 20 hours |
| 75% | 2 | 40 hours |
| 90% | 3.3 | 2.8 days |
| 97% (Dose Track's steady-state rule) | 5 | 4.2 days |
The longer the gap between doses compared with the half-life, the bigger the swing from peak to trough and the less the levels build up. These ratios do not depend on the amount.
| Interval | Peak : trough | Build-up vs one dose |
|---|---|---|
| Daily | 2.03 : 1 | 1.77× |
| Every other day | 4.38 : 1 | 1.23× |
| Twice weekly | 14.7 : 1 | 1.06× |
| Weekly | 267 : 1 | 1× |
| Every 2 weeks | over 1,000 : 1 | 1× |
Build-up is the accumulation ratio 1 / (1 − e−k·τ), with k = ln 2 / half-life and τ the interval.
After the last dose, about half is gone every 20 hours. After 5 half-lives, about 4.2 days, roughly 97% has cleared in the model.
There is no current FDA label for testosterone propionate injection. Small human studies of injection into muscle in oil point to an effective half-life of roughly 1 day: testosterone stayed above the lower limit of normal for 1 day after 25 mg and 2 days after 50 mg (Nieschlag 1976), and were back to baseline within 4 days after 100 mg (Anderson 1993). This is how long the oil depot keeps releasing, not how fast the body clears testosterone itself. No study reports a measured time to peak; testosterone was highest at the 8-hour sample in one study, and the ester stayed level from 3 to 36 hours in another (Fujioka 1986), so we do not list a single number.
The curve uses the half-life, time to peak, route and bioavailability built into the Dose Track app for testosterone propionate, and the same one-compartment model with first-order absorption. These are modeled estimates from published half-lives, drawn with the same one-compartment model as the Dose Track app. Real levels vary from person to person, and only a lab test measures them. This is not medical advice and not a dosing recommendation; dosing decisions belong with you and your prescriber.
Vial sizes and syringe math are in the Testosterone Propionate guide.
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