Description
What is Testosterone Undecanoate?
Testosterone Undecanoate, also known as Nebido, is a long-acting injectable testosterone ester. It’s the “marathon runner” of testosterone therapy—lasting for months after just a single injection. Unlike faster-acting forms like Testosterone Propionate, this version provides steady hormone levels over time, reducing the need for frequent injections.
Introduced globally in 2004 by Schering AG, Nebido is approved in many countries for the treatment of low testosterone. However, it is still awaiting FDA approval in the U.S. While it is mainly prescribed for medical hormone replacement therapy, some performance athletes also use it for its steady, sustained release.
How It Works
This compound is testosterone bound to the Undecanoate ester, which slows its release into the bloodstream. As a result, users experience stable testosterone levels without the sharp peaks and crashes common with shorter esters.
Its half-life is around three months—one of the longest among testosterone esters. For comparison, Testosterone Cypionate lasts roughly a week.
Key Benefits
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Long-lasting effects – fewer injections needed
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Improved nitrogen retention – supports muscle building
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Enhanced protein synthesis – faster recovery
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Increased IGF-1 production – boosts anabolic potential
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Higher red blood cell count – improves endurance
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Decreased glucocorticoid levels – reduces muscle breakdown
Because of its steady release, Testosterone Undecanoate works well for long-term hormone replacement therapy. In sports settings, it’s not the fastest option for quick gains, but it’s excellent for maintaining consistent testosterone levels.
Recommended Dosage
For medical use, the standard dose is 1,000mg every 12 weeks, with a follow-up dose at 6 weeks after the first. In performance settings, athletes sometimes use 1,000mg every 2–4 weeks, although other esters may be more suitable for short-term results.
Possible Side Effects
Estrogenic
As testosterone aromatizes into estrogen, side effects like water retention and gynecomastia can occur. Some users may require anti-estrogen therapy, either with Aromatase Inhibitors (AIs) or Selective Estrogen Receptor Modulators (SERMs).
Androgenic
Potential androgenic effects include acne, increased body hair growth, and hair loss in genetically predisposed individuals. Using a 5-alpha reductase inhibitor can help reduce these effects, though it may slightly lower testosterone potency.
Cardiovascular
In some cases, elevated blood pressure and changes in cholesterol levels may occur, especially when combined with an AI. Maintaining a healthy diet and lifestyle helps reduce these risks.
Why Choose Testosterone Undecanoate?
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Ideal for patients seeking low-maintenance testosterone replacement therapy
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Stable hormone levels for months
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Less frequent injections compared to other esters
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Suitable for long-term treatment plans
For other injectable options, see our full range of Injectable Steroids.
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