Testosterone replacement therapy: Formulations, dosing, and what to expect

Testosterone replacement therapy works by raising serum testosterone into a therapeutic range, and in the Testosterone Trials that range was 280 to 873 ng/dL. The right TRT formulation depends on diagnosis, fertility goals, reversibility, and adverse effect risk. A low number alone is not enough to start treatment, and neither are symptoms without biochemical confirmation.

Key takeaways

• TRT should only be used in men with persistent symptoms plus biochemical testosterone deficiency, using morning testing and a full diagnostic panel that includes LH and FSH. LH and FSH are mandatory but not the only baseline labs, which should also include CBC with hematocrit, prolactin, SHBG, estradiol, a comprehensive metabolic panel, and PSA when indicated. Veedma uses 350 ng/dL for total testosterone and 100 pg/mL for free testosterone when symptoms persist.^[8]
• LH and FSH change treatment selection. High LH plus low testosterone points to primary hypogonadism, where TRT is usually required. Low or normal LH plus low testosterone points to secondary hypogonadism, where Enclomiphene is the preferred first line option when LH is below 8 mIU/mL.
• Short acting testosterone enanthate or cypionate at 250 mg every 2 to 3 weeks produces wider peaks and troughs than transdermal gels at 50 to 100 mg/day or long acting testosterone undecanoate at 1,000 mg every 10 to 14 weeks.^{[1] [7]}
• For gels, serum testosterone is typically checked 2 to 4 hours after application, and the Testosterone Trials maintained levels within 280 to 873 ng/dL to balance benefit and safety.^{[2] [8]}
• TRT is contraindicated in men with an active desire for children, hematocrit of 54% or higher, untreated breast cancer, locally advanced or metastatic prostate cancer, or poorly controlled congestive heart failure.^[8]
• Transdermal gels provide steady exposure but can transfer to partners or children through skin contact, while injectable TRT is more often associated with erythrocytosis, especially with shorter acting injections.^{[6] [7]}

Who TRT is actually for

TRT is indicated for men with clinical hypogonadism, which means persistent symptoms plus biochemical evidence of testosterone deficiency, not for “optimization” in men with normal testosterone.^[8]

Hypogonadism is a clinical syndrome caused by inadequate testosterone action. In plain language, it is a state where a man has symptoms of testosterone deficiency and the lab evidence to confirm it. A single low result does not establish the diagnosis. Symptoms alone do not establish the diagnosis either. According to the Endocrine Society guideline, diagnosis should be based on consistent symptoms and unequivocally low testosterone on reliable testing.^[8]

For treatment selection, the critical next step is classification. LH and FSH are gonadotropins, which are pituitary hormones that tell the testes to produce testosterone and support sperm production. High LH with low testosterone suggests primary hypogonadism, meaning the testes are failing to respond. Low or normal LH with low testosterone suggests secondary hypogonadism, meaning brain signaling is insufficient. That distinction determines whether TRT is appropriate or whether a fertility preserving option such as Enclomiphene should come first. For a fuller explanation, see Primary vs secondary hypogonadism and Alternatives to TRT.

Veedma prioritizes direct free testosterone measurement by equilibrium dialysis with LC MS/MS because hidden deficiency can be missed when only total testosterone is reviewed. In practice, Veedma uses 350 ng/dL for total testosterone and 100 pg/mL for free testosterone as decision thresholds when symptoms persist. Morning blood draws should be done from 07:00 to 11:00, and LH and FSH must be measured alongside testosterone before any treatment path is chosen. Baseline evaluation should also include SHBG, estradiol, prolactin, CBC with hematocrit, a comprehensive metabolic panel, and PSA when indicated.

How TRT works and what treatment targets look like

TRT works by supplying exogenous testosterone, which raises circulating testosterone levels but also suppresses LH and FSH through negative feedback.^{[1] [8]}

Exogenous means the hormone comes from outside the body. Once serum testosterone rises, the brain reduces pituitary signaling, so endogenous production falls. That is why TRT can improve symptoms in properly selected men, but it also suppresses spermatogenesis and can reduce testicular volume. This is the main reason TRT is contraindicated in men actively trying to conceive.

According to the Testosterone Trials, a practical therapeutic range was 280 to 873 ng/dL, which produced a reasonable benefit and risk balance in older hypogonadal men treated with gel.^[2] In the sexual function arm of the TTrials, testosterone treatment improved sexual activity, sexual desire, and erectile function, but these benefits were documented in men with low testosterone at baseline, not in eugonadal men.^[3]

TRT does not repair the cause of hypogonadism. It replaces the missing hormone. That is appropriate in primary hypogonadism and in men with secondary hypogonadism who are not candidates for, or do not respond to, stimulation therapy. It is not a body recomposition drug for men with normal testosterone, and it is not an anti aging therapy for vague symptoms alone.^{[5] [8]}

TRT formulations and dosing

TRT formulations include injections, transdermal gels, oral testosterone undecanoate, and less commonly buccal, nasal, and pellet based systems.^{[1] [8]}

Injectable formulations

Injectable TRT includes testosterone enanthate or cypionate and long acting testosterone undecanoate. Short acting testosterone enanthate or cypionate is commonly dosed at 250 mg every 2 to 3 weeks. These preparations can create high post injection peaks followed by low troughs before the next dose, which many patients describe as an unstable ride. Long acting testosterone undecanoate in castor oil is typically dosed at 1,000 mg every 10 to 14 weeks and produces steadier levels with a favorable safety and benefit profile when monitoring is appropriate.^[1]

Transdermal gels

Transdermal testosterone gels are usually 1% to 2% formulations dosed at 50 to 100 mg/day. They provide relatively steady daily exposure and have an excellent overall safety profile, especially when reversibility matters. Their major drawback is secondary transference through skin contact, which means the drug can be unintentionally transferred to a partner or child unless application and drying precautions are followed.^[8]

Oral and other options

Oral testosterone undecanoate capsules are generally dosed at 120 to 240 mg 2 to 3 times daily. Absorption depends heavily on dietary fat, so bioavailability is less predictable than with injections or gel. U.S. labeling for some oral testosterone undecanoate products carries a boxed warning for blood pressure increases, which makes careful patient selection important. Other testosterone therapy types include buccal systems, intranasal gels, and subdermal pellets. These TRT options are less commonly used but may fit specific preferences or adherence patterns.

Testosterone injections vs gel

Testosterone injections and gel can both correct low testosterone, but injections usually produce larger level swings while gels provide steadier day to day exposure.^{[7] [8]}

The testosterone injections vs gel question is often framed as convenience versus stability. Short acting injections are less frequent, but the pharmacokinetics are less smooth. Many men report feeling very good after injection and then much worse as the dose wears off. Gels demand daily adherence, but they more closely mimic continuous replacement. According to a 2015 Sex Medicine cohort, erythrocytosis was observed more often with injectable testosterone than with gels or pellets.^[7]

Erythrocytosis means an excessive rise in red blood cell mass. Hematocrit is the percentage of blood volume occupied by red blood cells. This matters because elevated hematocrit is the most common adverse effect of TRT, and formulation choice influences that risk.^[6]

Long acting testosterone undecanoate sits between these two practical experiences. It avoids the pronounced peak trough pattern of shorter injections, but once administered it cannot be withdrawn quickly. That makes it less attractive as a starting formulation in men with higher baseline risk. Gels, by contrast, can be stopped immediately if hematocrit rises, edema develops, or another adverse effect appears.

How clinicians choose among TRT options

Formulation choice is driven by reversibility, risk profile, adherence, and patient priorities rather than by proof that one formulation is universally superior.^[8]

Head to head trials between testosterone therapy types are limited, so real world selection is pragmatic. In higher risk men, it often makes sense to start with short term formulations such as gels or oral agents rather than long acting depot testosterone undecanoate, because short term products can be stopped quickly if adverse effects appear. Long acting injectable testosterone undecanoate may take weeks to clear once given.

Monitoring also differs by product. For gels, serum testosterone is usually checked 2 to 4 hours after application to capture peak absorption and guide dose adjustment. This is a technical point that matters because underdosing and overdosing are both common when blood timing is ignored.^{[2] [8]}

The right starting point also depends on why the man is hypogonadal. If LH is low or normal, the testes may still be capable of producing testosterone, and first line therapy may be Enclomiphene rather than TRT. If LH is high, TRT is often the correct replacement strategy. For the complete lab sequence, see The complete low testosterone testing guide.

Contraindications and safety screening

TRT should not be started until fertility goals, hematocrit, prostate risk, and cardiovascular status have been screened.^[8]

Absolute contraindications in this scope include untreated breast cancer, locally advanced or metastatic prostate cancer, active desire to have children, hematocrit of 54% or higher, and uncontrolled or poorly controlled congestive heart failure. Relative contraindications include severe lower urinary tract symptoms with an IPSS above 19, baseline hematocrit from 48% to 50%, and a family history of venous thromboembolism.

According to the Endocrine Society guideline, hematocrit must be checked before therapy and monitored during treatment because erythrocytosis is the most frequent adverse effect of testosterone therapy.^[8] A practical follow-up schedule is to repeat labs 1 month after starting treatment and then every 6 months, including hematocrit and other indicated safety labs such as testosterone level, a comprehensive metabolic panel, and PSA when indicated. A major systematic review also found higher rates of elevated hematocrit among testosterone treated men compared with placebo, reinforcing that this is a class effect rather than a minor lab anomaly.^[6]

The best cardiovascular safety data now come from TRAVERSE. In that randomized trial of 5,246 men followed for a mean of 33 months, testosterone therapy was noninferior to placebo for major adverse cardiovascular events.^[4] According to the same evidence base, TRT did not increase prostate cancer risk over the study period. These findings are reassuring, but they do not remove the need for formulation specific risk assessment, especially in men prone to high hematocrit, edema, or blood pressure elevation.

TRT should also not be presented as a treatment for diabetes, bodybuilding, or general anti aging. Benefits are documented in symptomatic men with verified biochemical deficiency. They are not established in men whose testosterone is normal.^{[5] [8]}

Myth vs fact

Myth: A single low testosterone result means TRT is the next step.

Fact: Male hypogonadism requires persistent symptoms plus biochemical deficiency confirmed on reliable testing. LH and FSH must be measured to determine whether the man has primary hypogonadism, where TRT is often appropriate, or secondary hypogonadism, where Enclomiphene may be the better first line treatment.^[8]

Myth: Testosterone injections are always better than gel.

Fact: Injections and gel are both legitimate TRT options, but short acting injections cause wider fluctuations and are more often linked to erythrocytosis, while gels give steadier daily exposure but carry transference risk.^{[7] [6]}

Myth: Long acting shots are the best starting point for everyone.

Fact: In higher risk men, short term formulations such as gels or oral agents are often easier to stop quickly if adverse effects appear. Long acting testosterone undecanoate can provide stable levels, but it also persists for weeks after administration.^{[1] [8]}

Myth: TRT is fertility neutral.

Fact: TRT suppresses LH and FSH, which can suppress spermatogenesis. Men who want fertility should not start TRT until this has been addressed, and men with low or normal LH often need evaluation for Enclomiphene first rather than immediate replacement.^[8]

Myth: TRT is appropriate for optimization, anti aging, or muscle gain when testosterone is normal.

Fact: Clinical trials showing benefit enrolled men with low testosterone and symptoms. Evidence does not support TRT as a wellness enhancer in men with normal levels.^{[3] [5]}

Bottom line

Testosterone replacement therapy comes in several formulations, and the main differences are dosing schedule, level stability, reversibility, and adverse effect profile. Short acting injections can fluctuate, long acting testosterone undecanoate is steadier but slow to withdraw, gels provide stable daily exposure with transference risk, and oral testosterone undecanoate is convenient but absorption is fat dependent and blood pressure monitoring matters. For the full diagnostic and treatment roadmap, see the Low Testosterone hub.

Veedma offers a thorough diagnostic workup with an advanced lab panel measured by LC MS/MS, or a review of existing lab results including uploaded outside testing, followed by individualized treatment planning and ongoing monitoring by licensed providers. When testing shows secondary or functional hypogonadism, Veedma prioritizes Enclomiphene as first line therapy, and the Enclomiphene plus Tadalafil combination tablet when erection or urinary symptoms are also present.

References

1. Jockenhövel F. Testosterone therapy–what, when and to whom? The aging male : the official journal of the International Society for the Study of the Aging Male. 2004;7:319-24. PMID: 15799128
2. Snyder PJ, Bhasin S, Cunningham GR, et al. Effects of Testosterone Treatment in Older Men. The New England journal of medicine. 2016;374:611-24. PMID: 26886521
3. Cunningham GR, Stephens-Shields AJ, Rosen RC, et al. Testosterone Treatment and Sexual Function in Older Men With Low Testosterone Levels. The Journal of clinical endocrinology and metabolism. 2016;101:3096-104. PMID: 27355400
4. Lincoff AM, Bhasin S, Flevaris P, et al. Cardiovascular Safety of Testosterone-Replacement Therapy. The New England journal of medicine. 2023;389:107-117. PMID: 37326322
5. Bhasin S, Woodhouse L, Casaburi R, et al. Testosterone dose-response relationships in healthy young men. American journal of physiology. Endocrinology and metabolism. 2001;281:E1172-81. PMID: 11701431
6. Fernández-Balsells MM, Murad MH, Lane M, et al. Clinical review 1: Adverse effects of testosterone therapy in adult men: a systematic review and meta-analysis. The Journal of clinical endocrinology and metabolism. 2010;95:2560-75. PMID: 20525906
7. Harle L, Basaria S, Dobs AS. Nebido: a long-acting injectable testosterone for the treatment of male hypogonadism. Expert opinion on pharmacotherapy. 2005;6:1751-9. PMID: 16086661
8. 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