Testosterone Cypionate
Also known as Test C, Test Cyp, Depo-Testosterone
A long-ester injectable testosterone - the base of nearly every steroid cycle and the standard for prescribed TRT.
Medical status: FDA-approved for testosterone replacement therapy (TRT) in men with clinically confirmed low testosterone (hypogonadism).
Also commonly used for (off-label)
- Restoring energy, mood and libido on TRT
- Maintaining muscle, bone and strength as natural levels decline
- Body recomposition alongside training
Off-label and research uses are what people report, not approved indications. Talk to a clinician before using any of them.
Anabolic steroid — not a peptide
This compound is an anabolic steroid, not a research peptide. It has a different risk profile, legal status, and side-effect spectrum. The information here is for education only and is not medical advice or a recommendation to use. Read the medical disclaimer.
How it's taken
a deeper shot into a muscle, usually the glute, thigh, or shoulder
a small shot into the fat just under the skin (belly, thigh, or love handle)
Availability varies by supplier — injectable is the most commonly researched form.
New to peptides? Start with the beginner's guide.
- Documented dose
- 100–600 mg
- Typical frequency
- Once or twice per week
- Cycle
- 12 weeks on, 12 off
- Half-life
- Roughly 8 days
- Common vial sizes
- 200 mg, 250 mg
- Regulatory status
- Controlled anabolic steroid (Schedule III in the US). Legal only with a prescription. Listed for education and tracking only.
Dose on a U-100 syringe
This dose is too large to draw in one standard U-100 insulin syringe at common mixes. It is typically drawn from a larger vial, mixed at a higher concentration, or split into more than one injection. Run your own vial through the reconstitution calculator.
What it does
Testosterone cypionate is injectable testosterone attached to a long cypionate ester, which slows release so levels stay fairly steady between injections. It is used medically for testosterone replacement (typically 100-200 mg per week) and recreationally at higher doses for muscle and strength. Splitting the weekly amount into two injections keeps blood levels smoother.
Mechanism
Binds the androgen receptor to drive protein synthesis, nitrogen retention and red blood cell production. Aromatizes to estradiol, so estrogen-related effects are dose dependent. Shuts down natural testosterone production while running.
Storage — lyophilisedwhat's this?
Oil solution: store at room temperature away from light. No refrigeration needed.
Storage — reconstitutedwhat's this?
Keep the stopper clean with alcohol swabs and use within the labelled shelf life.
Reconstitution noteswhat's this?
Comes ready to inject in oil - no reconstitution. Draw with an 18-21g needle and inject with a 23-25g needle into glute, quad or delt, rotating sites.
Stacks well with
- TadalafilTRT handles the hormonal side; tadalafil covers daily blood flow and confidence.
- HCGAdded to maintain fertility and testicular function on TRT.
Popular combinations reported in the community and research literature — not a recommendation. Adding peptides multiplies side-effect risk; check with a clinician.
Commonly reported side effects
- Elevated estrogen: water retention, moodiness, gynecomastia
- Acne and oily skin
- Rising hematocrit / thicker blood
- Blood pressure increase
- Testicular shrinkage and suppressed natural production
- Accelerated male pattern hair loss in predisposed people
Contraindications noted
- Prostate or breast cancer
- Untreated high hematocrit or clotting disorders
- Uncontrolled high blood pressure or heart disease
- Trying to conceive
- Pregnancy or breastfeeding
- Under 21 years of age
Research notes
Well studied clinically at replacement doses. Supraphysiologic bodybuilding doses are not clinically studied for safety. Baseline and on-cycle bloodwork (total and free testosterone, estradiol, hematocrit, lipids, PSA where relevant) is essential.
Vendors carrying Testosterone Cypionate
These research suppliers list this compound. Prices, vial sizes and testing vary — always check the current lot certificate before you buy.
Peptide Streak does not sell peptides and is not affiliated with these vendors. Some list metabolic compounds under coded product names.