Testosterone Undecanoate (Castor Oil)
Testosterone ester in castor oil, injectable. Half-life 33.9 days.
Also called Nebido, Test U castor
Serum concentration from a single dose
single 100 mg dose over 24.2 weeks, vertical lines mark each half-life elapsed since the peak
What the numbers mean
The castor oil carrier slows release further, stretching the terminal half-life to 33.9 days against 20 days for the MCT preparation. Same molecule, same dose, so the difference is the vehicle alone. Plotted over a normal cycle length the curve looks almost flat after the loading phase.
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 Wiley.
Common questions about Testosterone Undecanoate (Castor Oil)
What is the half-life of Testosterone Undecanoate (Castor Oil)?
The model uses a terminal half-life of 33.9 days for Testosterone Undecanoate (Castor Oil). 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 Undecanoate (Castor Oil) take to reach steady state?
Roughly 24.2 weeks, 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 33.9 days that puts Testosterone Undecanoate (Castor Oil) at 24.2 weeks of climbing before the curve flattens.
How long does Testosterone Undecanoate (Castor Oil) stay in your system?
About 26.6 weeks 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 Undecanoate (Castor Oil) on a timeline with the rest of your cycle and watch the curves add up.
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