Testosterone Undecanoate (Testosterone Undecanoate (Ultra-Long Ester))
An ultra-long-acting testosterone ester available as a deep intramuscular injection (e.g. Nebido/Aveed) or oral capsule (Jatenzo). Used medically for TRT with very infrequent dosing. Educational reference only.
How it works
The large undecanoate ester dramatically slows release, giving weeks-long duration from a single injection. Oral undecanoate is absorbed via the lymphatic system, partly bypassing first-pass liver metabolism.
Key facts
- Molecular weight: 456.7 Da
- Half-life: ~20-34 days (injection depot)
- Bioavailability: Deep IM injection or oral (lymphatic absorption)
- Storage: Room temperature; protect from light.
Dosing overview
- Typical dose: Injection every ~10-14 weeks (medical); oral 2x daily with food
- Frequency: Infrequent (injection) or twice daily (oral)
- Duration: Ongoing (medical)
- Route: Deep intramuscular injection or oral
Protocol notes
- Injectable depot is dosed roughly every 10-14 weeks after a loading interval, under medical supervision.
- Oral undecanoate must be taken with fatty meals for lymphatic absorption, usually twice daily.
- Requires blood-work monitoring like other TRT forms.
Reported benefits
- Very infrequent injections (convenience)
- Stable long-term testosterone (medical)
- Oral option avoids most liver toxicity
- Restores testosterone in deficiency
Possible side effects
- Testosterone suppression
- Elevated hematocrit
- Estrogenic effects
- Rare pulmonary oil microembolism (injection)
- Blood pressure elevation (oral)
Research
- Long-acting testosterone undecanoate (2019): Provided stable physiological testosterone with dosing every ~10-14 weeks in hypogonadal men.
Compare Testosterone Undecanoate
Research and educational reference only. Not medical advice.