Testosterone Decanoate

Ester: Decanoate -- 10-carbon chain ester. The longest of the common injectable testosterone esters, sitting between Cypionate (8 carbons) and Undecanoate (11 carbons). Slow, flat release with no meaningful peak.

Testosterone content: ~65 mg of actual testosterone per 100 mg of Testosterone Decanoate (the ester accounts for ~35% of the molecular weight). Compare: Enanthate ~72 mg, Cypionate ~70 mg, Propionate ~84 mg, Undecanoate ~63 mg. A mg-for-mg swap from Enanthate to Decanoate delivers roughly 10% less testosterone.

Dosage:

• TRT / Cruise: 100-200 mg/week
• Enhancement: 300-600 mg/week for 14-20 weeks (run longer than an Enanthate cycle so steady state is actually reached)

Injection Protocol:

• Inject 1x/week (or 2x/week if splitting a large volume) -- the long half-life makes frequent pinning unnecessary
• IM: 25-27g needle, 1-1.5 inch, glutes/delts/VG
• SubQ viable at TRT doses with a 27-30g insulin needle, though the higher oil volume of UGL 200-250 mg/mL preparations suits IM better

Key Notes:

• No pharmaceutical standalone product exists anywhere. Every standalone "Test D 200/250" is UGL
• The best-known clinical use is as the 100 mg decanoate component of Sustanon 250, where it provides the sustained tail behind the propionate/phenylpropionate/isocaproate front end
• Steady state takes ~5-6 weeks (5 half-lives), so bloodwork drawn before week 6 will understate where the protocol lands
• Equally slow to clear, which makes it hard to titrate: a dose change takes over a month to show its full effect, and side effect management is reactive rather than immediate
• Clearance and PCT timing are two different numbers: the ester takes ~6-7 weeks to clear fully (5 half-lives), but PCT starts once levels have fallen far enough for a restart to work, at ~3 weeks. Waiting for full clearance just extends the shutdown
• Trough draws are less time-critical than with short esters because the curve is nearly flat between weekly injections

Where the decanoate ester sits against enanthate, cypionate and propionate: Testosterone esters compared.