What is Testosterone Undecanoate 250 (Astera Labs)?
Astera Labs testosterone undecanoate at 250mg/ml, in a 10ml multidose vial. The longest-acting testosterone ester, in the format that makes sense for a compound you inject every few weeks.
Also sold as Test-U, testosterone undecylate, Aveed, Nebido or Andriol.
The undecanoate ester is much larger than enanthate's, giving a half-life of twenty to thirty days against seven to ten. Injections are measured in weeks, blood levels are exceptionally flat, and it takes months rather than weeks to reach a true steady state.
Testosterone Undecanoate 250 benefits
- The flattest blood levels of any testosterone ester, with no weekly peak and trough
- Far fewer injections than any other option
- The standard choice for long-term testosterone replacement rather than cycling
- A vial suits it: draw an exact replacement dose rather than opening a fixed 1ml ampoule
- Suspended in Miglyol 812, thinner than the oils most competitors use
Testosterone Undecanoate 250 dosage
- Replacement
- 250 to 500mg every 2 to 4 weeks, which is 1 to 2ml
- Performance
- 500 to 750mg per week, run as a long-cycle base
- Frequency
- Weekly for performance, every 2 to 4 weeks for replacement
- Half-life
- 20 to 30 days
- Time to steady state
- 2 to 3 months
The long half-life is the whole point and also the whole problem. Steady state takes two to three months, so this is not a compound you judge at week four, and not one to use in a twelve-week cycle where it would spend most of the run still building.
Package content
- Vial
- 10ml sterile multidose
- Strength
- 250mg/ml
- Testosterone per vial
- 2500mg
- Carrier
- Miglyol 812
- Brand
- Astera Labs
On a replacement protocol at 250mg every two weeks, one vial covers twenty weeks.
Store below 30°C. Protect from light. Do not freeze. Keep out of reach of children.
Who is Testosterone Undecanoate 250 for?
People on long-term testosterone rather than people running cycles. If you are on replacement indefinitely, injecting every two to four weeks instead of twice a week is a meaningful difference to live with.
The vial arguably suits this compound better than ampoules do. Replacement doses are frequently not round millilitres, and a single vial lasts months, so there is far less repeated entry than with a weekly compound. TESTOMED U 250 is the same product as sealed ampoules at the same price if you prefer that.
Before you run it. The clearance time is the thing people underestimate. After stopping, undecanoate takes months to leave, which pushes
post-cycle therapy a long way out and makes this a poor choice if you intend to come off. Testosterone aromatises, which the
estrogen management guide covers, and
bloodwork matters more here than anywhere, because with levels this flat symptoms are your only other signal. Not for anyone under 18, and not for women who are pregnant or breastfeeding.
How to use Testosterone Undecanoate 250
Deep intramuscular injection, into the glute rather than a smaller muscle, because of the volume and the viscosity. Inject slowly, and wipe the stopper with alcohol before every draw. The injection technique guide covers the technique.
Frequently asked questions
How often do I inject testosterone undecanoate?
For replacement, every two to four weeks. The twenty to thirty day half-life means levels hold across that gap without dropping meaningfully.
For performance use at higher doses, weekly is more common, because you are aiming for a much higher level and getting there faster matters.
Why does it take so long to work?
Any compound takes roughly four to five half-lives to reach steady state. With a half-life of twenty to thirty days, that is two to three months.
Judging it at week four tells you nothing. This is the ester where patience is not optional.
Is a vial or ampoules better for this one?
The vial, for most people. Replacement doses are often 0.6ml or 1.4ml rather than round numbers, and an ampoule forces you to a fixed 1ml or waste the rest.
A vial also gets entered far less often here than with a weekly compound. Ten doses spread across five months is not a contamination concern the way fifteen draws a month would be.
Is this the same as Nebido?
Same compound. Nebido and Aveed are brand names for testosterone undecanoate, prescribed at 1000mg every ten to fourteen weeks under medical supervision.
The ester and the hormone are identical, the difference is the protocol built around it.
Do I need PCT?
If you come off, yes, but the timing is difficult. Undecanoate takes months to clear, so post-cycle therapy started too early is wasted.
That is a real argument against choosing this ester if you intend to cycle rather than stay on.
