Testosterone Undecanoate (MCT Oil)
TU MCT · Testosterone Undecanoate
MCT-carried testosterone undecanoate; shorter apparent half-life than the castor-oil formulation.
Key takeaways
- MCT-carried variant of the longest testosterone ester; reference products (Nebido, Aveed) use castor oil.
- ~20-day half-life, peak around day 8–9; injections every 8–12 weeks.
- Half-life and peak are estimates calibrated from published TU data, not MCT-specific measurements.
- Full testosterone monitoring applies, and dose changes take months to register in bloodwork.
Reported dosing protocols
Protocols reported in research literature and clinic/community use — informational context, not a dosing recommendation.
| Use case | Dose | Route | Frequency | Duration |
|---|---|---|---|---|
| TRT (community, MCT carrier) | 500–1000 mg | IM | Every 8–12 weeks | Ongoing |
Pharmacokinetic summary
- Model tier
- Advanced (t½ + Cmax + Tmax + F)
- Half-life
- 20 days
- Cmax
- 750 ng/dL
- Tmax
- 8.5 days
- Bioavailability
- 65%
- Typical dose
- 500–1000 mg
Harm reduction
- Aromatizes
- Yes
- DHT derivative
- No
- Injection frequency
- Every 8–12 weeks
Frequently asked questions
Does the carrier oil actually change the curve?
Yes, somewhat. Castor oil is more viscous and slows depot release; MCT releases faster, so apparent half-life shortens and the interval tightens from 10–14 weeks toward 8–12. Exact MCT figures are estimates, since the carrier itself has no dedicated human PK study.
Is MCT-carried TU an approved product?
No. Approved injectable TU (Nebido, Aveed) uses castor oil. MCT versions come from compounding pharmacies or underground labs, which adds concentration and sterility uncertainty on top of the PK differences.
How long until a dose change shows up?
Months. With a ~20-day half-life, serum levels take several months to reach the new steady state. Bloodwork drawn a few weeks after a change mostly reflects the old dose; trough testing right before an injection gives the clearest read.
References
- Estimated PK (MCT carrier) — Cmax calibrated to ng/dL serum peak; MCT carrier yields a shorter apparent half-life than castor.
- Wang et al., J Androl 2010 — 84-week injectable TU trial — Phase III PK and safety data for injectable TU in hypogonadal men (castor-oil formulation).
- Bayer Nebido Prescribing Information — Label dosing schedule and PK parameters for the castor-oil reference product.
Related compounds
Testosterone Enanthate
Long-acting testosterone ester; the most common TRT and cycle base. Reaches steady state in ~5 weeks.
Testosterone Cypionate
Standard US TRT ester with a slightly longer release tail than enanthate. Steady state ~4–5 weeks.
Testosterone Propionate
Short-acting ester with sharp peaks; requires frequent injection. Useful for frontloading.
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