Testosterone Isocaproate
Test Iso
Sustanon component with medium duration. Simple model — peak calibrated from sibling esters.
Key takeaways
- Medium-chain ester found almost only in blends (60 mg of Sustanon 250), rarely used standalone.
- Modeled ~3-day half-life, calibrated from sibling esters — no dedicated human PK studies exist.
- Same harm-reduction profile as any testosterone: aromatizes, suppresses, monitor the standard set.
Reported dosing protocols
Protocols reported in research literature and clinic/community use — informational context, not a dosing recommendation.
| Use case | Dose | Route | Frequency |
|---|---|---|---|
| Blend component (Sustanon 250) | 60 mg per 250 mg ampoule | IM | Per blend schedule (typically 1–2× weekly) |
Pharmacokinetic summary
- Model tier
- Simple (t½ + F, Tmax estimated)
- Half-life
- 3.1 days
- Cmax
- 86.5 ng/dL
- Bioavailability
- 75%
- Typical dose
- 50–200 mg
Harm reduction
- Aromatizes
- Yes
- DHT derivative
- No
- Injection frequency
- 2×/week
Frequently asked questions
Is isocaproate the same as caproate?
No. Isocaproate is the branched isomer of caproate (hexanoate), with slightly different release kinetics. Sustanon historically used isocaproate; some older blends used the straight-chain caproate. Practically they occupy the same medium-duration slot.
Why not just use a single ester?
Blends like Sustanon were designed to give a fast onset plus a long tail from one injection. In practice the mixed release makes blood levels bumpier than a single longer ester like enanthate or cypionate at the same weekly dose, which is why many TRT protocols prefer single esters.
Can you buy testosterone isocaproate on its own?
It is not marketed as a standalone pharmaceutical. Grey-market single-ester vials exist, but nearly all human exposure data comes from Sustanon/Omnadren use, which is why the PK model here is calibrated rather than measured.
References
- TAU ester PK review — Cmax calibrated to ng/dL serum peak.
- Translational Andrology and Urology 2016 — Pharmacology of testosterone replacement preparations — Ester pharmacology review covering the Sustanon components.
Related compounds
Testosterone Enanthate
Long-acting testosterone ester; the most common TRT and cycle base. Reaches steady state in ~5 weeks.
Testosterone Cypionate
Standard US TRT ester with a slightly longer release tail than enanthate. Steady state ~4–5 weeks.
Testosterone Propionate
Short-acting ester with sharp peaks; requires frequent injection. Useful for frontloading.
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