hormonemusclesexual healthlongevity

Testosterone Cypionate

Also known as Test Cyp, Test C, Depo-Testosterone, TC

A long-acting injectable form of testosterone and the most commonly prescribed option for testosterone replacement therapy (TRT). One injection keeps levels elevated for days.

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.

How it's taken

Intramuscular injection
a deeper shot into a muscle, usually the glute, thigh, or shoulder
Subcutaneous injection
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.

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Typical frequency: 1–2 injections per week (every 3.5–7 days)
Half-life: Around 8 days
Regulatory status: FDA-approved prescription medication (Schedule III controlled substance) for male hypogonadism

What it does

Testosterone cypionate replaces or tops up the testosterone your body no longer makes enough of. Restoring levels into a healthy range is typically associated with better energy, mood, libido, muscle mass, bone density and body composition. Typical TRT dosing is 100–200 mg per week, usually taken as one or two injections, and always adjusted against bloodwork and symptoms with a prescriber.

Mechanism

Testosterone is attached to a cypionate ester, which slows how quickly it is released from the injection site into the bloodstream. Enzymes gradually cleave the ester, freeing active testosterone over roughly a week. Free testosterone then binds androgen receptors throughout the body. Some of it converts into estradiol and DHT, which drive part of its benefits — and part of its side effects.

Storage — reconstitutedwhat's this?

Store the vial at controlled room temperature (about 20–25°C / 68–77°F), away from direct light. Do not refrigerate or freeze — the oil can crystallize. If crystals form, warm the vial in your hands or in warm water until it goes clear before drawing.

Reconstitution noteswhat's this?

No mixing needed — testosterone cypionate comes pre-dissolved in oil, most often at 200 mg/mL. At that concentration, a 100 mg dose is 0.5 mL (50 units on a U-100 syringe). Because the oil is thick, many people draw with a larger needle (21–23G) and switch to a smaller one (25–27G) for the injection itself.

Stacks well with

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

Acne and oily skin
Rising hematocrit (thicker blood) — monitored with regular bloodwork
Water retention and mild blood-pressure increases
Breast tenderness or gynecomastia from estrogen conversion
Testicular shrinkage and suppressed sperm production
Hair shedding in people genetically prone to hair loss
Injection-site soreness
Mood or energy swings when injections are spaced too far apart

Contraindications noted

Known or suspected prostate or male breast cancer
Elevated hematocrit that is not being managed
Untreated severe sleep apnea
Uncontrolled heart failure
Trying to conceive — TRT suppresses natural sperm production
Pregnancy or breastfeeding

Research notes

TRT is one of the most studied hormone therapies in medicine. Regular monitoring is standard of care: total and free testosterone, estradiol, hematocrit/hemoglobin, PSA and lipids — typically checked 3–6 months after starting and every 6–12 months once stable. Subcutaneous injection (into belly or thigh fat with a small needle) has become a popular alternative to intramuscular shots and produces similarly stable levels in studies.