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

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

Written by

Alexander Grant, MD, PhD: Urologist & Men’s health advocate

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

TRT injections work when dosed in physiologic ranges like about 50 mg twice weekly, yet they also suppress LH and FSH and can drop sperm counts. Know how to dose, test, and protect fertility.

“You can feel better on injections fast, but dosing and lab follow up matter. Keep levels steady, watch hematocrit and PSA, and plan ahead if you want children.”

Alexander Grant, MD, PhD — Urologist and researcher specializing in men’s reproductive health and hormone balance

The relationship

Testosterone cypionate is a long acting injectable form of testosterone used for hypogonadism, which means low testosterone with symptoms. When used at physiologic doses, it improves sexual desire and erectile function in symptomatic men with confirmed low levels. These effects are supported by randomized trials and society guidelines from 2018 onward [1,2].

The strongest trials show clear gains in sexual measures when baseline total testosterone is in the low range. Meta analyses report benefits when men start below about 350 ng per deciliter, which equals 12 nmol per liter [7,8]. If total testosterone is borderline, check free testosterone; values below about 100 pg per mL, which equals 10 ng per dL, support the diagnosis when symptoms persist [1,7].

Injection schedules shape how you feel. Biweekly 200 mg dosing can cause high peaks near 1100 ng per dL with lows near 400 ng per dL by day fourteen [3,5]. Weekly plans, such as 100 mg once a week, smooth those swings; many men split that to about 50 mg twice each week for steadier levels in daily life [3,4].

How it works

Absorption and peaks

After an intramuscular shot of testosterone cypionate, serum levels rise over 24 to 48 hours. A common two week 200 mg plan produces peak levels above 1200 ng per dL with a fall toward 400 ng per dL by the end of the interval [3,5]. Weekly dosing reduces the swing between peak and trough [3,4].

Brain feedback and gonadotropins

Exogenous testosterone shuts down the hypothalamic pituitary testicular axis (the brain to testis loop that sets production). This lowers luteinizing hormone (LH) and follicle stimulating hormone (FSH), which reduces intratesticular testosterone and sperm production [1,12]. Suppression can be rapid within weeks on full dose therapy [10,11].

Aromatization and estradiol

Some injected testosterone converts to estradiol through the enzyme aromatase. With high peaks, estradiol can rise several fold, which may add breast tenderness or mood swings in a small group of men [3]. Lower, steadier levels blunt that rise [3,4].

Red cell production

Testosterone raises hematocrit, the share of blood made of red cells. The main safety signal is erythrocytosis at hematocrit above 54 percent. If that occurs, pause therapy or lower the dose and consider phlebotomy per guidelines from 2018 [1].

Decision thresholds

Use these practical cut points when symptoms persist: total testosterone below 350 ng per dL or free testosterone below 100 pg per mL. If total testosterone is borderline, measure free testosterone before you decide [1,7].

Conditions linked to it

  • Fertility plans: TRT injections suppress LH and FSH and can lower sperm count to very low levels. Most men recover after stopping, yet recovery can take 3 to 12 months and sometimes up to 24 months; older age and longer use slow recovery [9,11,12].
  • Cardiovascular risk: The TRAVERSE outcomes trial, published June 16, 2023, in 5246 men, found testosterone therapy was noninferior to placebo for major adverse cardiac events over a mean 33 months; some adverse events like atrial fibrillation and pulmonary embolism were numerically higher and need caution [6].
  • Prostate: Modest PSA rises are common. Large trials and guidelines show no clear short term rise in prostate cancer risk with proper screening, but monitoring remains standard [1,2,6].
  • Sleep apnea and red cell rise: TRT can worsen untreated sleep apnea and increases hematocrit; both call for careful follow up [1].

Limitations: Cardiovascular data are strongest for transdermal therapy and for men with confirmed hypogonadism. Data for other groups, longer timelines, and head to head injection schedules are more limited [1,6].

Symptoms and signals

  • Low sexual desire or fewer morning erections.
  • Fatigue, lower drive, slower recovery after workouts.
  • Low mood or irritability.
  • Increased body fat and lower muscle strength.
  • Sleep issues and snoring.
  • On therapy: acne, breast tenderness, rising hematocrit, or higher blood pressure.
  • On therapy without fertility protection: lower semen volume and sperm count.

What to do about it

  1. Test right. Get two early morning total testosterone tests on different days. Add free testosterone if totals are borderline. Use 350 ng per dL for total or 100 pg per mL for free as decision thresholds when symptoms persist [1,7]. Check LH, FSH, prolactin, CBC with hematocrit, and PSA per age and risk [1,2].
  2. Choose a steady plan. A common start is 100 mg per week of testosterone cypionate, often split to about 50 mg twice weekly to reduce peaks and troughs. Recheck levels after 4 to 8 weeks and aim for mid normal range while keeping symptoms in view [2,3,4]. If you plan a child, avoid TRT or add a fertility plan such as hCG or a SERM under a urologist’s care [1,12,13].
  3. Monitor on a schedule. Check hematocrit and testosterone at 3 months, then at 6 to 12 months. Hold or lower the dose if hematocrit passes 54 percent. Track PSA per age and risk. Watch blood pressure and symptoms at each visit [1,2].

Myth vs Fact

  • Myth: “TRT injections always ruin fertility.” Fact: Most men recover sperm counts after stopping, though it can take months; age and duration matter.
  • Myth: “Higher peaks mean better results.” Fact: Very high peaks raise estradiol and side effects without better outcomes; steady levels feel better for many.
  • Myth: “Normal PSA means you can skip checks.” Fact: You still need regular PSA and exam per guidelines.
  • Myth: “TRT always harms the heart.” Fact: A large 2023 trial showed no excess in major cardiac events in properly selected men on therapy.

Bottom line

Injectable testosterone cypionate can lift desire and energy when you have true low levels and it is dosed to keep levels steady. Protect fertility before you start. Use clear thresholds, steady dosing, and regular labs to get the benefit while you manage the risks [1,2,3,6].

References

  1. Bhasin S, Brito JP, Cunningham GR, et al. 2018. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab 103(5):1715–1744. PMID: 29562364
  2. Mulhall JP, Trost LW, Brannigan RE, et al. 2018. Evaluation and Management of Testosterone Deficiency: AUA Guideline. J Urol 200(2):423–432. PMID: 29601923
  3. Pastuszak AW, Gomez LP, Scovell JM, Khera M. 2021. Pharmacokinetics of testosterone therapies in relation to diurnal variation of serum testosterone levels as men age. Int J Impot Res 33(5):516–523. PMID: 34239014 (PMC article: PMC9293229)
  4. Shoskes JJ, Wilson MK, Spinner ML. 2016. Pharmacology of testosterone replacement therapy preparations. Transl Androl Urol 5(6):834–843. PMID: 28124637 (PMC article: PMC5182226)
  5. Dobs AS, Meikle AW, Arver S, et al. 1999. Pharmacokinetics, efficacy, and safety of a permeation enhanced testosterone transdermal system vs biweekly testosterone enanthate injections. J Clin Endocrinol Metab 84(10):3469–3478. PMID: 10522982
  6. Lincoff AM, Bhasin S, Flevaris P, et al.; TRAVERSE Study Investigators. 2023. Cardiovascular Safety of Testosterone Replacement Therapy. N Engl J Med 389(2):107–117. Published June 16, 2023. PMID: 37326322
  7. Corona G, Rastrelli G, Morgentaler A, et al. 2017. Meta analysis of Results of Testosterone Therapy on Sexual Function Based on International Index of Erectile Function Scores. J Sex Med 14(6):777–794. PMID: 29120213
  8. Isidori AM, Giannetta E, Greco EA, et al. 2005. Effects of testosterone on sexual function in men: a meta analysis. J Clin Endocrinol Metab 90(7):3838–3850. PMID: 15963411
  9. McBride JA, Carson CC, Coward RM. 2016. Recovery of spermatogenesis following testosterone replacement therapy or anabolic androgenic steroid use. Asian J Androl 18(3):373–380. PMID: 26835422 (PMC article: PMC4854084)
  10. Ly LP, Liu PY, Swerdloff RS, et al. 2005. Rates of suppression and recovery of human sperm output in testosterone based hormonal contraceptive regimens. Hum Reprod 20(6):1733–1740. PMID: 15860500
  11. Liu PY, Handelsman DJ, Anderson RA, et al. 2006. Rate, extent, and modifiers of spermatogenic recovery after hormonal male contraception. Lancet 367(9520):1412–1420. PMID: 16650651
  12. Kohn TP, Louis MR, Pickett SM, et al. 2017. Age and duration of testosterone therapy predict time to return of sperm count after hCG and SERM therapy. Fertil Steril 107(2):351–357.e1. PMID: 27855957
  13. Patel AS, Leong JY, Ramos L, Ramasamy R. 2018. Testosterone Is a Contraceptive and Should Not Be Used in Men Who Desire Fertility. World J Mens Health 37(1):45–54. PMID: 30405965 (PMC article: PMC6305868)
  14. Mottet N, Salonia A, et al. 2025. Update on Sexual and Reproductive Health Guidelines from the European Association of Urology. Eur Urol 88(1):12–14. PMID: 39867856
  15. Wang C, Nieschlag E, Swerdloff RS, et al. 2022. Testosterone Replacement Therapy in Hypogonadal Men. World J Mens Health 40(1):12–31. PMID: 34871882 (PMC article: PMC8994707)

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