Testosterone Cypionate: Dosing and Tracking

Quick Reference

• What it is: Testosterone cypionate, a long-acting testosterone ester
• What it treats: Male hypogonadism (low testosterone); also used in gender-affirming hormone therapy
• How it's administered: Intramuscular (IM) or subcutaneous (SubQ) injection
• Standard dosing range: 100-200 mg per week (TRT); varies by indication
• Available concentrations: 100 mg/mL and 200 mg/mL
• Half-life: ~8 days
• Common needle gauges: 22-25G 1"-1.5" (IM); 27-30G 1/2" (SubQ)

Testosterone cypionate is the most commonly prescribed testosterone ester for replacement therapy in the United States. It's an oil-based injectable with an 8-day half-life, available as 100 mg/mL and 200 mg/mL concentrations. Unlike the pre-filled pen devices used for GLP-1 medications, testosterone cypionate requires drawing from a multi-dose vial with a syringe -- which means there's more to get right with each injection. This page covers the pharmacology, dosing, injection technique for both IM and SubQ routes, side effects, bloodwork monitoring, and tracking.

What Testosterone Cypionate Is

Testosterone cypionate is a synthetic ester of testosterone, the primary male sex hormone. The cypionate ester is attached to the testosterone molecule to slow its release after injection, creating a depot in the muscle or subcutaneous tissue that gradually releases testosterone into the bloodstream over approximately one week.

It's sold under the brand name Depo-Testosterone (Pfizer) and is widely available as a generic. The two standard concentrations are:

• 200 mg/mL -- the most commonly prescribed. A typical 100 mg dose is 0.5 mL.
• 100 mg/mL -- sometimes preferred when smaller, more precise volumes are needed.

The vehicle is cottonseed oil (brand) or sesame oil (some generics). If you have a seed oil allergy, confirm the vehicle with your pharmacist. Testosterone enanthate (in castor oil/benzoate) is an alternative ester with a nearly identical half-life.

Multi-dose vials typically contain 1 mL or 10 mL. The 10 mL vials are more cost-effective but require careful handling -- preservative (benzyl alcohol) is included, but contamination is still a concern if injection technique is poor.

How It Works

Testosterone cypionate delivers exogenous testosterone that acts on androgen receptors throughout the body. Once the ester is cleaved in the bloodstream, the released testosterone is biochemically identical to endogenous testosterone.

Key physiological effects:

• Muscle protein synthesis: Testosterone is a primary driver of muscle mass maintenance and growth. Low testosterone leads to measurable loss of lean mass.
• Bone mineral density: Testosterone supports osteoblast activity. Hypogonadal men are at increased risk of osteoporosis.
• Erythropoiesis: Testosterone stimulates red blood cell production via EPO signaling. This is both a therapeutic effect (correcting anemia of hypogonadism) and a safety concern (polycythemia).
• Libido and sexual function: Androgen receptors in the brain mediate sexual desire. Testosterone is the primary hormonal driver.
• Mood and cognition: Low testosterone is associated with fatigue, irritability, and cognitive fog. Replacement often improves these symptoms, though the relationship is not perfectly linear.
• Fat distribution: Testosterone influences body composition, reducing visceral fat accumulation and supporting lean mass.

Once on exogenous testosterone, the hypothalamic-pituitary-gonadal (HPG) axis suppresses endogenous production. This means your testes stop producing testosterone (and sperm production may decline or cease). This is not a side effect -- it's the expected pharmacological consequence of exogenous administration. It's also why stopping TRT abruptly can cause a period of symptomatic low testosterone until endogenous production recovers (if it recovers fully, which is not guaranteed after prolonged use).

Approved Uses

Testosterone cypionate is FDA-approved for:

Testosterone replacement therapy in males with conditions associated with a deficiency or absence of endogenous testosterone:

• Primary hypogonadism (testicular failure)
• Hypogonadotropic hypogonadism (pituitary/hypothalamic failure)

It is also widely used off-label for:

• Gender-affirming hormone therapy in transmasculine individuals
• Late-onset hypogonadism (age-related testosterone decline), though the FDA indication technically requires documented pathological hypogonadism

The Endocrine Society guidelines recommend TRT for men with consistently low morning total testosterone (typically below 300 ng/dL on two separate measurements) combined with clinical symptoms of hypogonadism.

Dosing

Testosterone cypionate dosing is highly individualized. There is no universal "correct" dose -- your prescriber titrates based on symptom response and bloodwork.

Common dosing ranges

Why twice-weekly dosing is gaining favor: With an 8-day half-life, a single weekly injection creates a noticeable peak (24-48 hours post-injection) and trough (days 6-7). Some patients feel this fluctuation as a cycle of energy and mood changes through the week. Splitting the weekly dose into two injections (e.g., 75 mg Monday and 75 mg Thursday) flattens the curve considerably. The total weekly dose stays the same -- only the frequency changes.

Dose adjustments: Your prescriber adjusts based on trough testosterone levels (drawn the morning before your next injection), symptom response, hematocrit, and estradiol. The typical target is a trough total testosterone of 500-700 ng/dL, though individual goals vary.

Volume calculations: At 200 mg/mL, a 150 mg dose is 0.75 mL. At 100 mg/mL, the same dose is 1.5 mL. IM sites can handle up to ~3 mL per injection. SubQ is typically limited to 0.5-0.7 mL per site for comfort, which is one reason SubQ works best with twice-weekly protocols at lower per-injection volumes.

Injection Sites and Technique

Testosterone cypionate can be administered IM or SubQ. Both routes are clinically validated, though IM has a longer history of use and SubQ is increasingly common in modern TRT protocols.

Intramuscular (IM)

Needle: 22-25 gauge, 1-1.5 inches depending on body composition. 23G x 1" is a common all-purpose choice.

IM technique:

1. Draw the prescribed volume using an 18G draw needle (testosterone in oil is thick -- drawing with a small gauge takes forever).
2. Switch to your injection needle (23-25G).
3. Select and clean the injection site with an alcohol swab.
4. Insert the needle at a 90-degree angle in a swift, deliberate motion.
5. Aspirate briefly (pull back the plunger slightly) to check for blood. If blood appears, withdraw and try a different site. Note: aspiration is debated in current guidelines, but many TRT practitioners still recommend it for IM injections.
6. Inject slowly and steadily -- rushing increases post-injection pain.
7. Withdraw the needle, apply light pressure with a cotton ball.
8. Dispose of the needle in a sharps container.

Subcutaneous (SubQ)

Needle: 27-30 gauge, 1/2 inch. Insulin syringes (1 mL) work well for the volumes used in twice-weekly protocols.

SubQ sites:

• Abdominal fat: 1-2 inches from the navel. Pinch a fold of skin, inject at 45-90 degrees depending on subcutaneous fat depth.
• Upper thigh fat pad: Lateral or anterior thigh.
• Love handle area: Lateral abdominal fat.

SubQ technique:

1. Draw using an 18G or the injection needle (smaller volumes are feasible with 27-30G, though slower).
2. Pinch a fold of skin at the injection site.
3. Insert the needle at a 45-90 degree angle into the fat layer.
4. Inject slowly.
5. Release the skin fold, remove the needle, apply light pressure.

SubQ injection produces a slower, more gradual absorption curve than IM, which some patients prefer. Research published in The Journal of Sexual Medicine found comparable serum testosterone levels between SubQ and IM routes. SubQ also causes less injection site pain and is easier to self-administer for most people.

Site rotation

Rotate every injection. For twice-weekly IM protocols, that means at least 4 sites in your rotation (e.g., left ventrogluteal, right ventrogluteal, left vastus lateralis, right vastus lateralis). For SubQ, rotate across abdominal quadrants and thigh sites.

Our TRT injection log and site rotation guide covers rotation systems in detail.

Side Effects to Track

Common

• Acne and oily skin: Androgen-driven sebaceous gland activation. Often most noticeable in the first few months, then stabilizes. More common at higher doses.
• Fluid retention: Mild water retention and bloating, particularly in the first weeks of treatment. Usually self-limiting.
• Mood changes: Some patients report irritability, anxiety, or mood swings, particularly at peak levels. Twice-weekly dosing often reduces this.
• Hair thinning: In those genetically predisposed to androgenic alopecia. Testosterone accelerates the process -- it doesn't cause it in people without the genetic predisposition.
• Injection site pain/soreness: Variable. Post-injection pain (PIP) is more common with certain oil vehicles and with IM injections. Warming the vial to body temperature before injecting and injecting slowly both help.

Clinically significant

• Elevated hematocrit (polycythemia): The most important safety concern. Testosterone stimulates red blood cell production. Hematocrit above 54% increases the risk of blood clots, stroke, and other thromboembolic events. Regular CBC monitoring is non-negotiable. If hematocrit rises too high, treatment options include dose reduction, more frequent (lower per-dose) injections, therapeutic phlebotomy (blood donation), or temporary suspension of TRT.
• Estradiol elevation: Testosterone aromatizes to estradiol. Elevated estradiol can cause gynecomastia (breast tissue growth), water retention, and emotional lability. Monitored via bloodwork. Some prescribers use aromatase inhibitors (anastrozole) to manage this, though the practice is debated.
• Testicular atrophy: Expected consequence of HPG axis suppression. The testes shrink because they're no longer producing testosterone. HCG is sometimes co-prescribed to maintain testicular volume and intratesticular testosterone.
• Reduced fertility: Exogenous testosterone suppresses FSH and LH, which reduces or halts sperm production. This can be reversible but is not guaranteed. If fertility preservation matters, discuss HCG or other strategies with your prescriber before starting TRT.
• Lipid changes: Some patients see a decrease in HDL and/or an increase in LDL. Monitor lipids regularly.
• Sleep apnea: TRT can worsen pre-existing obstructive sleep apnea. Report new snoring, daytime fatigue, or breathing disturbances during sleep.

What to Monitor

Bloodwork schedule

Trough levels: Always draw blood in the morning, right before your next injection (not after). This gives your prescriber the lowest point in your cycle -- the most useful number for dose adjustment.

Self-monitoring

• Symptoms: Track energy, libido, mood, sleep quality, and exercise recovery. These are the subjective markers that tell you whether your dose is dialed in.
• Injection details: Date, time, dose, site, side, any PIP or reactions.
• Body composition: Waist measurement, weight, and subjective muscle/fat assessment. Changes are gradual -- monthly measurements are more useful than daily.
• Blood pressure: TRT can affect BP through fluid retention and erythropoiesis. Check weekly, especially in the first 3 months.

Comparison to Alternatives

Testosterone cypionate and enanthate are nearly interchangeable -- similar half-lives, similar dosing, similar results. The choice often comes down to availability, oil vehicle preference, and prescriber habit. Cypionate is more common in the US; enanthate is more common internationally.

Undecanoate (Aveed) eliminates self-injection entirely -- you get an in-office injection every 10 weeks. The trade-off is less dosing flexibility and a required 30-minute post-injection observation period due to a small risk of pulmonary oil microembolism.

Transdermal gels provide daily testosterone delivery without injections but carry a risk of transfer to partners or children through skin contact, require daily application, and produce lower peak levels than injections.

Tracking Your Treatment

TRT is an ongoing protocol, not a one-time prescription. Doses change, bloodwork needs to be scheduled and reviewed, injection sites need rotation, and the subjective experience of treatment evolves over months. Without a system, things slip -- missed injections, lopsided site rotation, bloodwork that doesn't get drawn.

What to log every injection:

• Date and time
• Dose (in mg) and volume (in mL)
• Concentration (100 or 200 mg/mL) -- especially important if your pharmacy switches generics
• Route (IM or SubQ)
• Injection site and side (e.g., "right ventrogluteal" or "abdomen, lower-left")
• Needle gauge and length
• Post-injection notes (PIP, bleeding, lumps)
• Next injection date

Additionally, track:

• Bloodwork dates and key results (total T trough, hematocrit, estradiol)
• Symptom trends (energy, mood, libido, sleep -- weekly rating)
• Vial lot number and expiration date

Done Dose handles TRT tracking natively. Log IM or SubQ injections, rotate through your site map, set reminders for your injection schedule, and keep your bloodwork results organized so you're ready for every prescriber visit. When your protocol changes -- dose adjustment, new frequency, route switch -- update it once and the app adjusts.

Frequently Asked Questions

How often do you inject testosterone cypionate?

Most TRT protocols call for injection every 7 days (once weekly) or every 3.5 days (twice weekly). Twice-weekly protocols produce more stable blood levels and fewer peak-trough symptoms. Some protocols use every-two-week dosing, but this produces significant hormonal fluctuations and is increasingly considered suboptimal.

What is the half-life of testosterone cypionate?

Approximately 8 days. This means that after injection, blood testosterone levels peak within 24-48 hours and then gradually decline over the following week. The 8-day half-life is why weekly or twice-weekly injection schedules maintain more stable levels than biweekly protocols.

Can you inject testosterone cypionate subcutaneously?

Yes. SubQ injection of testosterone cypionate is increasingly common in TRT protocols. Research shows comparable absorption to IM injection with potentially less pain and easier self-administration. Typical SubQ sites include the abdominal fat and the fat pad of the upper thigh. Needle gauge is usually 27-30G, 1/2 inch.

What bloodwork do you need on TRT?

At minimum: total testosterone, free testosterone, estradiol, hematocrit/CBC, PSA (men over 40 or with risk factors), lipid panel, and metabolic panel. Most clinicians check these at 6-8 weeks after starting or changing dose, then every 3-6 months once stable.

What are the side effects of testosterone cypionate?

Common side effects include acne, oily skin, fluid retention, mood changes, and elevated hematocrit. Estradiol can rise due to aromatization, potentially causing gynecomastia or water retention. Hematocrit elevation is the most clinically significant safety concern requiring regular monitoring -- levels above 54% typically require intervention.

Sources

1. Bhasin S, et al. "Testosterone Therapy in Men with Hypogonadism: An Endocrine Society Clinical Practice Guideline." The Journal of Clinical Endocrinology & Metabolism, 2018. DOI: 10.1210/jc.2018-00229
2. Al-Futaisi AM, et al. "Subcutaneous Testosterone Is Effective and Safe as an Alternative to Intramuscular Injection." The Journal of Sexual Medicine, 2021. DOI: 10.1016/j.jsxm.2021.01.014
3. Mayo Clinic. "Testosterone therapy: Potential benefits and risks as you age." mayoclinic.org
4. Pfizer. "Depo-Testosterone (testosterone cypionate) Prescribing Information." pfizer.com
5. Fujioka M, et al. "Pharmacokinetics of Testosterone Cypionate after Intramuscular Injection." European Journal of Endocrinology, 1986. DOI: 10.1530/eje.0.1530055

Done Dose tracks your testosterone cypionate protocol -- IM or SubQ, any frequency, with site rotation, dose logging, and bloodwork reminders. Download Done Dose to keep your TRT dialed in.