Testosterone Сypionate: Relief you can feel, but what about fertility?

Testosterone cypionate can restore drive, energy, and mood in men with true low testosterone, but it also shuts down sperm production if you are not careful. Here is how to use it wisely, protect fertility, and know if it is really right for you.

The relationship

Testosterone cypionate is a long-acting injectable form of testosterone used to treat hypogonadism, which means both low testosterone and symptoms such as low libido, fatigue, and depressed mood. It is injected into a muscle or under the skin and slowly releases testosterone over several days, creating a smoother hormone curve than short-acting injections.^[1]

Large guideline reviews from the American Urological Association and European Association of Urology show that men with total testosterone below about 350 ng/dL, or about 12 nmol/L, and consistent symptoms are the ones most likely to benefit from testosterone replacement therapy, including testosterone cypionate.^[1] If total testosterone is borderline, checking free testosterone, the unbound and “active” portion, adds clarity. Levels below about 100 pg/mL (≈10 ng/dL) support a diagnosis of hypogonadism when symptoms are present.

The same research that highlights symptom relief also makes one trade-off very clear. Testosterone cypionate reliably suppresses luteinizing hormone, or LH, and follicle-stimulating hormone, or FSH. LH and FSH are pituitary hormones that normally tell the testes to make testosterone and sperm. When those signals are shut down by external testosterone, natural testosterone production falls and sperm counts often drop sharply.

How it works

To understand testosterone cypionate, you need to understand how normal testosterone production is wired and what happens when you add an external source. Several connected systems work together, and testosterone cypionate changes them all.

Hormone replacement with a slow-release backbone

Testosterone cypionate is testosterone attached to a “cypionate” ester, a chemical side-chain that slows release from the injection site. After an intramuscular or subcutaneous injection, the ester is gradually removed by enzymes, releasing active testosterone into the bloodstream over 3 to 7 days depending on dose, site, and individual metabolism.

Clinical studies comparing dosing schedules show that smaller, more frequent injections, such as 50 to 60 mg twice weekly, produce more stable testosterone levels with fewer peaks and crashes than larger doses given every 1 to 2 weeks. More stable levels tend to cause fewer mood swings and less fluctuation in libido.

Turning down the brain’s control knobs

The hypothalamic–pituitary–gonadal axis is the hormone loop connecting the brain and testes. The hypothalamus releases GnRH, or gonadotropin-releasing hormone, which tells the pituitary gland to release LH and FSH. LH then tells the testes to make testosterone, and FSH helps drive sperm production.

Adding testosterone cypionate raises blood testosterone. The brain senses this and reduces GnRH, LH, and FSH output through negative feedback, the same safety system that prevents testosterone from going sky-high in healthy men. With lower LH and FSH, the testes shrink activity and often physically shrink in size over time.

Effects on sperm production and fertility

Spermatogenesis is sperm production inside the testes. It depends heavily on FSH and on high local testosterone levels inside the testicles, which are much higher than levels measured in blood. When LH and FSH fall because of external testosterone cypionate, sperm counts usually drop, sometimes to near zero.^,[2]

Randomized trials done as part of male contraceptive research show that giving healthy men testosterone injections can suppress sperm counts to levels compatible with contraception in most participants. Recovery of sperm production after stopping testosterone typically occurs, but can take 3 to 12 months, and is slower in older men and those treated for longer periods.^[2]

Diagnostic thresholds and who benefits most

Meta-analyses and international guidelines agree that men with symptoms plus total testosterone below 350 ng/dL are the most likely to see clear benefits from testosterone replacement therapy, including testosterone cypionate.^[1] When total testosterone is between 300 and 400 ng/dL, measuring free testosterone, with a practical decision threshold around 100 pg/mL, helps separate true hypogonadism from normal variation.

Trials in men with normal or borderline testosterone have found smaller and less consistent benefits, alongside the same risks of fertility suppression and potential side effects. That is why major societies recommend using testosterone cypionate only when there is both low lab value and a clear symptom pattern.^[1]

Routes of injection and dose considerations

Testosterone cypionate can be injected into the gluteal or thigh muscles, or into the fat just under the skin. Studies suggest that subcutaneous injections at appropriate doses deliver similar testosterone levels and symptom relief, with less injection pain for many patients.

For most men, total weekly doses in the range of 80 to 150 mg, divided into two or more injections, are sufficient to bring testosterone into the mid-normal range without excessive peaks. Higher doses increase the risk of elevated red blood cell counts, acne, and irritability without proven added benefit in controlled trials.^[1],[3]

Conditions linked to it

Testosterone cypionate can bring real relief when used for the right reasons. It can also create or worsen health problems if misused or poorly monitored. Here are the main issues backed by clinical evidence.

• Fertility suppression: As noted above, testosterone cypionate suppresses LH and FSH, often leading to much lower sperm counts and sometimes temporary infertility. Studies of testosterone as a male contraceptive show that the majority of men see sperm counts fall below 1 million per milliliter, a level where natural conception is unlikely.^[2]
• Elevated red blood cell count: Testosterone stimulates erythropoiesis, or red blood cell production. This can lead to polycythemia, which is an abnormally high hematocrit or proportion of red cells in blood. Hematocrit above roughly 54 percent is linked to higher risk of blood clots and needs dose adjustment or phlebotomy.^[3]
• Prostate-related concerns: Testosterone does not appear to cause prostate cancer in most men, but it can increase prostate volume and prostate-specific antigen, or PSA, especially in the first 6 to 12 months.^[4] Men with untreated high-risk prostate cancer should not use testosterone cypionate, and all men on therapy need regular PSA and prostate exams.
• Cardiovascular risk signals: Research on testosterone therapy and heart risk is mixed. Some observational studies report higher rates of heart events, while others show improved or neutral outcomes, especially when therapy is used to restore physiological levels rather than supraphysiologic ones. A 2023 FDA review concluded that data do not show a large excess risk but warrant careful use in men with existing cardiovascular disease.
• Mood and sleep changes: Many men report better mood, reduced irritability, and improved sleep on well-dosed testosterone cypionate, especially if they started with depression or fatigue linked to low testosterone. Very high peaks, however, can trigger irritability, anxiety, or insomnia. Untreated sleep apnea may worsen on therapy and should be evaluated.

Limitations note: Much of the cardiovascular and prostate risk data comes from observational studies rather than randomized controlled trials, which means cause and effect cannot be proven with certainty. Older men with more health problems are also more likely to be prescribed therapy, which can skew results.

Symptoms and signals

Men usually come to testosterone cypionate because they feel off, not because of a lab number. Here are symptoms and signals linked to low testosterone, and to testosterone cypionate itself.

Symptoms that may suggest low testosterone before treatment:

• Low sex drive or less interest in sex than usual
• Fewer morning erections
• Trouble getting or keeping an erection despite stimulation
• Low energy or “crashing” by mid-afternoon
• Loss of muscle mass or strength despite training
• Increased body fat, especially around the waist
• Low mood, irritability, or “flat” feeling
• Brain fog, trouble focusing, or slower thinking
• Reduced shaving frequency or body hair growth
• Smaller testicles or reduced firmness in the scrotum

Signals to watch once you start testosterone cypionate:

• Improving libido, energy, and mood in the first 4 to 12 weeks
• Changes in testicle size or scrotal “fullness,” which often decrease
• Acne, oily skin, or increased body hair
• Swelling in the ankles or sudden weight gain from fluid retention
• Shortness of breath, headaches, or facial redness, which can signal high hematocrit
• Worsening snoring, gasping at night, or daytime sleepiness, suggesting possible sleep apnea
• Breast tenderness or swelling from conversion of testosterone to estrogen in some men
• Changes in mood, such as feeling more on edge, especially right after injections

If you are trying to conceive, one crucial signal is missing: you will not feel your sperm count dropping. The only way to track fertility impact is semen analysis before starting therapy and at intervals if future fertility matters to you.

What to do about it

If you are considering testosterone cypionate, or already on it, you can approach it in a structured way. Here is a practical 3-step plan.

1. Get properly tested before you start
   • Test morning total testosterone on at least 2 separate days between about 7 and 10 a.m., when levels are highest.
   • If total testosterone is between 300 and 400 ng/dL, ask for free testosterone. A value below about 100 pg/mL makes true hypogonadism more likely in a symptomatic man.^[1]
   • Check LH, FSH, and prolactin to understand whether the problem is mainly in the testes or higher up in the pituitary.
   • Get baseline hematocrit, PSA, and a digital rectal exam, especially if you are over 40 or have urinary symptoms.
   • If you care about future fertility, get a semen analysis before starting testosterone cypionate. Freezing sperm before therapy is a reasonable safety net for men at high risk or who may delay childbearing.
2. Use lifestyle and the right kind of treatment
   • Work on the basics: sleep at least 7 hours, maintain a healthy weight, strength train 2 to 3 times per week, and reduce excess alcohol. Weight loss of 5 to 10 percent can raise testosterone in many overweight men without medication.
   • If tests show clear hypogonadism and symptoms remain, discuss testosterone cypionate with a urologist or endocrinologist. For many men, doses around 80 to 150 mg per week, split into 2 injections, are enough to restore mid-normal levels.
   • If fertility is a priority, ask about alternatives like clomiphene citrate, which is a selective estrogen receptor modulator that stimulates your own LH and FSH, or hCG, which is a hormone that mimics LH and can keep testicular function active. These can sometimes be used alone or alongside lower doses of testosterone cypionate under specialist care.
3. Monitor and adjust over time
   • Recheck testosterone levels, hematocrit, and PSA about 3 months after starting testosterone cypionate, then every 6 to 12 months once stable.^[1]
   • Keep hematocrit below roughly 54 percent. If it climbs higher, your clinician should lower the dose, extend the dosing interval, or consider therapeutic blood donation.^[3]
   • Track how you feel using simple notes on libido, energy, mood, sleep, and gym performance. Dose changes should be guided by both labs and how you actually feel, not numbers alone.
   • If you decide to stop testosterone cypionate, work with your clinician on a plan. Some men may use short courses of clomiphene or hCG to support recovery of natural production, especially after long-term therapy.

Myth vs Fact

• Myth: “Testosterone cypionate is basically a natural supplement.”
  Fact: It is a prescription hormone drug that powerfully alters your endocrine system and can shut down sperm production. It is not comparable to over-the-counter boosters in potency or risk.
• Myth: “Once you start testosterone cypionate, you can never come off it.”
  Fact: Many men can taper off and recover natural production, especially after shorter courses. Recovery can take months and may be incomplete in some men, which is why starting for the right reasons matters.
• Myth: “If a little testosterone helps, more is always better.”
  Fact: Studies show that bringing levels into a mid-normal range improves symptoms. Going far above normal mainly increases side effects like high hematocrit, acne, and irritability without proven health benefit.^[3]
• Myth: “Testosterone therapy causes prostate cancer.”
• Fact: Current evidence does not show that physiologic testosterone replacement causes prostate cancer, although it can uncover or accelerate disease already present. Men with known high-risk cancer should avoid it, and all men on therapy need routine screening.^[4]
• Myth: “If my libido is low, testosterone cypionate is the obvious fix.”
  Fact: Low desire has many causes, including stress, relationship issues, depression, medications, and sleep problems. Testosterone helps most when low libido occurs alongside proven low testosterone, not in isolation. You may benefit from also exploring non-hormonal causes in a resource focused on low libido when the brain is the issue.

Bottom line

Testosterone cypionate can be life-changing for men with true hypogonadism, restoring sexual desire, energy, and mood when used in doses that mirror normal physiology. The same drug can temporarily switch off sperm production and raise health risks if used casually, at high doses, or without proper monitoring. If you are thinking about testosterone cypionate, anchor the decision in solid testing, clear symptoms, and a plan that protects both your current health and your future fertility.

References

1. Mulhall JP, Trost LW, Brannigan RE, et al. Evaluation and Management of Testosterone Deficiency: AUA Guideline. The Journal of urology. 2018;200:423-432. PMID: 29601923
2. Liu PY, Swerdloff RS, Anawalt BD, et al. Determinants of the rate and extent of spermatogenic suppression during hormonal male contraception: an integrated analysis. The Journal of clinical endocrinology and metabolism. 2008;93:1774-83. PMID: 18303073
3. Bhasin S, Brito JP, Cunningham GR, et al. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. The Journal of clinical endocrinology and metabolism. 2018;103:1715-1744. PMID: 29562364
4. Morgentaler A, Traish A. The History of Testosterone and the Evolution of its Therapeutic Potential. Sexual medicine reviews. 2020;8:286-296. PMID: 29661690