Testosterone Propionate
Testosterone ester, injectable. Half-life 24.9 hours.
Also called Test P, Prop
Serum concentration from a single dose
single 100 mg dose over 5.2 days, vertical lines mark each half-life elapsed since the peak
What the numbers mean
A 24.9 hour half-life produces a visibly serrated curve on anything less frequent than every other day. The light ester leaves about 84% active testosterone per mg, the highest of the esterified forms, and this compound anchors the calibration for the whole testosterone family.
The active fraction is the share of each milligram the model treats as reaching circulation as active compound. For an injectable that is ester weight: a milligram of enanthate is not a milligram of testosterone. For an oral it is bioavailability, the share that survives the gut and the liver, which is why some orals sit far below 100%. How the model works.
Where these numbers come from
The half-life and the peak concentration are both read from a published reference. Read it on PubMed.
The reference above records a 50 mg dose peaking near 1159 ng/dL, and that is the figure used. An older tracer study of the same ester reports peaks several times higher and could not be reconciled with it, so the lower and better documented value was kept. Propionate sets the scale for the whole testosterone family, so this choice moves every testosterone curve on the site.
Common questions about Testosterone Propionate
What is the half-life of Testosterone Propionate?
The model uses a terminal half-life of 24.9 hours for Testosterone Propionate. For an injectable that figure is the rate the oil depot releases the compound rather than the rate the body clears it, which is why it runs longer than the half-life of the ester itself.
How long does Testosterone Propionate take to reach steady state?
Roughly 5.2 days, on a schedule that does not change. Steady state is conventionally taken as five half-lives, the point at which each dose is clearing about as fast as the next one arrives, and at a half-life of 24.9 hours that puts Testosterone Propionate at 5.2 days of climbing before the curve flattens.
How long does Testosterone Propionate stay in your system?
About 5.7 days after the last dose for the serum level to fall to a few percent of where it was, on the same five-and-a-half half-life reasoning. That is the modelled blood level only. It is not a detection window: metabolites are found by testing long after the parent compound has gone, and this model says nothing about that.
Put Testosterone Propionate on a timeline with the rest of your cycle and watch the curves add up.
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