The ester attached to the 17β-hydroxyl of injectable AAS is the primary determinant of blood level kinetics, injection frequency requirements, washout timing, and steady-state achievement. Selecting the correct ester for a research protocol is as important as selecting the correct compound.
Ester half-lives govern: how quickly a compound reaches steady-state (4–5 half-lives), how stable blood levels are between doses, how quickly the compound clears after discontinuation, and how many half-lives separate the first injection from peak blood levels.
* Approximate half-lives from published pharmacokinetic studies. Oral AAS not shown (3-9 hr range). Research reference only.
| Compound | Ester | Carbon Chain | Half-Life | Steady-State | QSC Available |
|---|---|---|---|---|---|
| Testosterone | Undecanoate | C11 | ~21 days | ~10-12 weeks | Special order |
| Nandrolone | Decanoate (DECA) | C10 | ~15 days | ~10-12 weeks | Yes — 200mg/mL |
| Boldenone | Undecylenate (EQ) | C11 unsaturated | ~14 days | ~10 weeks | Yes — 300mg/mL |
| Testosterone | Cypionate | Cyclopentylprop (~C8) | ~8 days | ~5-6 weeks | Yes — 250mg/mL |
| Testosterone | Enanthate | C7 | ~7 days | ~4-5 weeks | Yes — 250mg/mL |
| Trenbolone | Enanthate | C7 | ~7 days | ~4-5 weeks | Yes — 200mg/mL |
| Masteron | Enanthate | C7 | ~7 days | ~4-5 weeks | Yes — 200mg/mL |
| Nandrolone | Phenylpropionate (NPP) | Phenyl + C3 | ~5 days | ~3-4 weeks | Yes — 100mg/mL |
| Testosterone | Propionate | C3 | ~2 days | ~1.5 weeks | Yes — 100mg/mL |
| Trenbolone | Acetate | C2 | ~2 days | ~1.5 weeks | Yes — 100mg/mL |
| Masteron | Propionate | C3 | ~2 days | ~1.5 weeks | Yes — 100mg/mL |
| MENT | Acetate | C2 | ~1-2 days | ~1 week | Yes — 50mg/mL |
| Testosterone | Suspension (no ester) | None | <1 day | ~3 days | Yes — 100mg/mL |