Testosterone Undecanoate
Ultra-long-ester testosterone. Used for TRT with infrequent injections (every 10-14 weeks). Brand names: Nebido, Aveed.
Overview
Ultra-long-ester testosterone. Used for TRT with infrequent injections (every 10-14 weeks). Brand names: Nebido, Aveed.
Same as other testosterone esters: elevates testosterone, estradiol (via aromatization), suppresses LH/FSH, increases haemoglobin/haematocrit, worsens lipids (moderate)
Compound Guide
Ester: Undecanoate -- 11-carbon chain ester dissolved in castor oil. Ultra-slow release providing stable testosterone levels over 10-14 weeks from a single injection.
Dosage:
- TRT: 1000 mg (4 mL) every 10-14 weeks after an initial loading phase (second injection at 6 weeks)
- Not typically used for enhancement due to the extremely long half-life and slow dose adjustment
Injection Protocol:
- Deep IM injection only (gluteal), 21-23g needle, 1.5-2 inch
- Must be injected very slowly (over 2 minutes minimum) due to the 4 mL oil volume
- Administered in-clinic in many countries due to rare pulmonary oil microembolism (POME) risk
- Not suitable for SubQ injection
Key Notes:
- Preferred TRT option in Australia, UK, and Europe (Nebido); available in the US as Aveed
- Eliminates the need for weekly injections, improving adherence
- Slower dose titration: takes 2-3 injections (20-30 weeks) to reach steady state
- Bloodwork timing is different from short esters: test at the midpoint or trough (week 8-10) of the injection interval
- Aromatisation is typically lower and more stable than with shorter esters due to the flat release curve
- Not practical for PCT transitions due to the extremely long clearance time (3-4 months)
Usage History
Markers to Monitor
Frequently Asked Questions
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Quick Reference
Category
AAS
Half-Life
20-21 days
Detection Time
5+ months