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Testosterone Cypionate

Extensively Studied

Testosterone cypionate (Depo-Testosterone) is the US-dominant long-ester injectable testosterone — pharmacologically indistinguishable… | AAS · Oil injectable

Aliases (5)
Test-C · Depo-Testosterone · T-Cyp · Cypionate · Test Cyp
TYPICAL DOSE
100-200 mg IM/SubQ weekly (TRT)
ROUTE
Intramuscular injection (oil)
CYCLE
8-12 week cycle + PCT
STORAGE
Room temp; protect from light
✎
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▸ Vial inspection & sterile draw AAS oil

AAS oil arrives pre-suspended in carrier oil — no BAC water needed. Inspect for clarity, color, and crashed compound (cold storage can crystallize). Warm vial in palm or under hot tap before draw.

Steps
  1. 1 Wipe vial stopper with isopropyl alcohol.
  2. 2 Warm vial 30-60s in palm if oil is cold/cloudy.
  3. 3 Draw with 18g needle into 22-25g pin barrel for IM, or 27-29g for sub-Q.
  4. 4 Tap out air bubbles, expel a small drop, then inject at chosen site.
Open dose calculator for Testosterone Cypionate
▸ Cycle structure & PCT AAS
Ester
cypionate
Frequency
weekly
PCT
Required
Phase 1 — On cycle

Ramp dose over week 1, hold steady through cycle weeks. Track baseline labs (TT/FT/E2/SHBG/HCT/lipids/LFTs) at week 0; recheck at week 4 and end-of-cycle.

Phase 2 — Bridge / cease

On the last dose, the ester clears over its half-life window (cypionate = est. 8 days). PCT begins after the active compound has cleared.

Phase 3 — PCT (post-cycle therapy)

Standard PCT is enclomiphene 12.5-25 mg/day or clomid 50/50/25/25 over 4 weeks (or nolvadex 20/20/10/10). HCG bridge optional during cycle to preserve testicular volume + faster restart. Bloodwork at PCT week 4 + 8 to confirm HPG axis recovery (LH, FSH, TT back to baseline).

▸ Overview TL;DR

Testosterone cypionate (Depo-Testosterone) is the US-dominant long-ester injectable testosterone — pharmacologically indistinguishable from enanthate at the receptor (same molecule, slightly longer ester → slightly smoother release). Gold-standard TRT for documented hypogonadism, AAS workhorse base ester everywhere else. SKIP-AT-20 for Dylan: HPG axis at lifetime peak, no eugonadal benefit established, real fertility/lipid/Hct risks. Revisit at 35-40+ only if natural T crosses symptomatic threshold; even then, enclomiphene-first for fertility preservation.

▸ Mechanism of action
  • Molecule: Bioidentical testosterone, esterified at the 17β-hydroxyl with cyclopentanepropionate (cypionic acid). Identical anabolic/androgenic activity to enanthate, propionate, undecanoate — the ester is just a release-rate modifier.
  • Half-life: ~8 days (vs enanthate ~7 days, sustanon mixed ~10 days, propionate ~1 day, undecanoate ~21 days). The extra day buys very slightly smoother levels per dose interval, which is why US TRT clinics overwhelmingly default to cypionate.
  • Steady state: ~5 half-lives → 5-6 weeks at fixed weekly dose. Practical implication: blood draws to titrate are meaningless before week 6.
  • Release kinetics: IM oil depot (cottonseed or grapeseed oil typically); ester cleaved by plasma esterases liberating free testosterone over days. SubQ administration (Xyosted-style or off-label) produces flatter PK with less peak-trough swing — increasingly preferred in modern TRT.
  • Receptor activity:
    • AR (androgen receptor): Full agonist; drives muscle protein synthesis, RBC production via EPO, libido, secondary sex characteristics, behavioral effects.
    • 5α-reductase → DHT: Skin (acne, MPB), prostate, scalp, CNS effects amplified.
    • Aromatase (CYP19) → estradiol: ~0.3% conversion baseline, dose-dependent; supraphysiologic T → high E2 → gyno, water retention, mood lability. AI co-administration in BB protocols; rarely needed at TRT doses.
    • GR cross-talk: Modest anti-glucocorticoid effect at supraphysiologic levels.
  • HPG suppression: Negative feedback at hypothalamus (GnRH↓) and pituitary (LH↓, FSH↓) → testicular atrophy + spermatogenesis collapse. Recovery time after long cycles: 3-18 months, sometimes never (especially with longer cycles, higher doses, age >35, or pre-existing low FSH baseline).
▸ Pharmacokinetics Approximate
t½: ~8 days (IM oil depot)
100% 50% 0% 0 10d 2.9w 4.3w 5.7w t½ Peak

Approximate decay curve drawn from the half-life mention(s) in the source notes. Real PK data not yet ingested per compound.

▸Research protocols2 protocols
GoalDoseFrequencySoloCycle
TRT (clinical replacement, hypogonadism only):100-200 mg IM/SubQ once weekly OR 50-100 mg twice weekly (split dosing flatter — increasingly preferred)once weekly——
Performance / supraphysiologic (NOT recommended for Dylan):300-600 mg/wk × 10-16 weeks + AI + PCT (SERM)2x/week—10-16 week

Auto-extracted from dosing notes. For full context including caveats and Dylan-specific protocols, see the Dosing protocols section.

▸Quality indicators5 checks
✓
Clear oil
Yellow tint is normal (carrier oil); cloudiness or sediment is not.
✓
No particulates
Hold the vial up to light. Floaters mean discard, not filter.
!
Color matches ester
Test E is light yellow; Tren A is amber. Off-color suggests under-dosing or wrong compound.
✓
Sterile draw technique
Always swab vial top, fresh needle for draw, fresh needle for injection.
!
Crashed gear is recoverable
Holosteric carrier crashes when cold. Warm to body temp; if still cloudy, discard.
▸ What to expect From notes
  1. 1
    Onset
    (TRT 100-200 mg/wk): Subtle. Energy, morning erections, sleep, mood improve over 2-6 weeks. Body comp shift…
  2. 2
    Onset
    (supraphysiologic 400-600 mg/wk): Noticeable libido + drive surge within 1-2 weeks, training aggression, fa…
  3. 3
    Peak
    Plateau by week 4-6. Sustained anabolic effect for cycle duration.
  4. 4
    Taper
    / post-cycle: Without PCT, crash 2-3 weeks post-last-injection (one ester half-life clearance). Profound fa…
▸ Side effects + safety
  • Common (>10% users at suppressive dose):
    • Testicular atrophy (universal at suppressive doses without hCG)
    • Decreased spermatogenesis / oligospermia / azoospermia
    • Acne, oily skin
    • Water retention / edema (E2-mediated)
    • Increased hematocrit / hemoglobin (less aggressive than enanthate at equal dose, anecdotally)
    • Injection site soreness (PIP — less PIP than propionate, equivalent to enanthate)
  • Less common (1-10%):
    • Gynecomastia (E2-driven, especially without AI in supra dosing)
    • Mood lability / irritability / aggression — variable, dose-dependent
    • Sleep apnea worsening
    • Accelerated androgenic alopecia (in genetically susceptible — SRD5A2 dependent)
    • Lipid panel deterioration (HDL ↓, LDL/ApoB ↑) — typically less severe than oral 17αAA but real
    • Cottonseed oil allergy (rare; some compounders use grapeseed or MCT alternatives)
  • Rare-serious (<1% but worth knowing):
    • Polycythemia → thromboembolic risk (DVT, PE, stroke). Phlebotomy or blood donation if Hct >54%.
    • Cardiomyopathy / LVH at chronic supraphysiologic exposure (years).
    • Permanent fertility loss — reported even after PCT in some cases. Risk highest with longer cycles, higher doses, age >35, low baseline FSH.
    • Prostate hypertrophy / unmasking subclinical prostate cancer.
    • Sterile abscess at injection site (poor technique / contaminated UGL gear).
    • Hepatic effects: minimal with injectables (vs oral 17αAA like methyltestosterone).
  • Specific watch periods:
    • First 8-12 weeks: monitor hematocrit, E2, libido response, mood.
    • 3 months: full lipid + comprehensive panel.
    • Annually: PSA + DRE if >40 or family history.
▸Interactions8 compounds
  • Anastrozole / aromatase inhibitor:Synergistic
    Manages E2 at supraphysiologic doses. Rarely needed at TRT doses; over-suppression of E2 produces joint pain, low libido, lipid issues — modern TRT trends aw…
  • hCG (250-500 IU 2x/wk):Synergistic
    Maintains testicular volume + intratesticular T for fertility preservation in younger TRT patients; can be combined with cyp lifelong.
  • Enclomiphene:Synergistic
    Ironically used DURING cyp in some "stacked" TRT protocols to preserve LH/FSH signal — relatively novel approach.
  • Finasteride (caveat):Synergistic
    For hair preservation — blocks 5α-reductase; controversial trade-off (post-finasteride syndrome risk; possibly attenuates anabolic effect in muscle).
  • Methyltestosterone or other oral 17αAA:Avoid
    Hepatotoxic; redundant + dangerous. See methyltestosterone.md — strictly dominated.
  • Trenbolone / Deca / other AAS in young men:Avoid
    Each adds specific harms (Tren = neuro/CV/sleep nightmare; Deca = prolactin, "deca dick", much longer suppression).
  • High-dose stimulants (modafinil + caffeine + ECA stacks):Avoid
    Compounds CV strain (HR + BP + Hct).
  • Alcohol (heavy):Avoid
    Compounds lipid + BP + hepatic load.
▸References4 sources

Depo-Testosterone (testosterone cypionate) — FDA label

current FDA prescribing information; PK, dosing, contraindications, drug interactions.

accessdata.fda.govView →

WADA Prohibited List 2026

2026

S1 exogenous androgen classification (banned in and out of competition).

wada-ama.orgView →

Testosterone cypionate — DrugBank DB13943

pharmacology, mechanism, indications, interactions.

go.drugbank.comView →

Testosterone cypionate — PubChem CID 5995

chemical structure, CAS 58-20-8.

pubchem.ncbi.nlm.nih.govView →
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