How to Treat Low Testosterone: TRT Explained

Low testosterone is more than a lab number. It's fatigue that doesn't lift no matter how much you sleep, strength that's harder to build and easier to lose, a libido that flatlined. A mood that's just... off. Millions of men are living with it — and most never get a formal diagnosis, let alone treatment (Zitzmann et al., 2025).

Treatment for low testosterone is well-studied and genuinely effective when it's the right fit. The harder part is getting the diagnosis right, choosing the right approach, and understanding what comes with it.

The short answer: Testosterone replacement therapy (TRT) is FDA-approved for men with confirmed hypogonadism — two morning testosterone measurements below 300 ng/dL, plus symptoms. The right formulation depends on your lifestyle, fertility goals, and medical history. TRT works, but it's not for everyone, and it comes with real tradeoffs that deserve an honest conversation.

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What Does "Low Testosterone" Actually Mean?

Low testosterone is defined by two morning blood draws below 300 ng/dL — plus symptoms. One number on one day is not a diagnosis. Your doctor saying your labs look "fine" doesn't mean much without the actual number: testosterone at 290 ng/dL is below threshold, and that's where a lot of men start feeling the effects.

The FDA and clinical guidelines set the diagnostic threshold at below 300 ng/dL on two separate morning measurements (Bhasin et al., 2023). The "two measurements" requirement is not a technicality. Testosterone fluctuates throughout the day and across days — a single low reading is not sufficient to diagnose hypogonadism. Both draws need to happen in the morning, when testosterone is at its peak, for the result to be meaningful.

Beyond the number, there are two types of hypogonadism:

• Primary hypogonadism — the testes aren't producing enough testosterone despite adequate hormonal signaling. This includes conditions like Klinefelter syndrome, testicular injury, or prior chemotherapy.
• Secondary (hypogonadotropic) hypogonadism — the signaling from the brain (LH and FSH from the pituitary) is insufficient, so the testes don't get the right instructions.

The FDA has approved testosterone therapy for both of these. What it has not established as an indication is age-related (late-onset) hypogonadism — the gradual T decline that comes with getting older in an otherwise healthy man. Treatment in that population is considered off-label and requires a different conversation about risk-benefit (Tsametis & Isidori, 2018).

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What Are the Treatment Options for Low Testosterone?

Testosterone replacement therapy is not one thing. It's a category of treatments with meaningfully different pharmacokinetics, delivery methods, and practical tradeoffs. Here's what the options actually look like (Barbonetti et al., 2020):

Injections

The most common starting point. Testosterone cypionate and testosterone enanthate are injected intramuscularly every one to two weeks. Testosterone undecanoate (brand name Aveed) is a longer-acting injection given every 10 weeks.

The tradeoff with weekly injections: you get peaks and troughs. Levels spike shortly after the injection and then decline before the next one. Some men feel the difference toward the end of the cycle. The 10-week undecanoate option smooths that out, but requires office administration due to a rare risk of serious pulmonary oil microembolism.

Transdermal Gels

Daily application gels — including AndroGel, Testim, and Axiron — maintain steadier testosterone levels than injections. The main concern is secondary transfer: if a child or female partner comes into contact with the application site before it's fully dry, they can absorb testosterone. Application to the shoulders or upper arms (not the genitals) and washing hands afterward reduces that risk significantly.

Subcutaneous Pellets

Testopel pellets (75 mg each) are inserted subcutaneously and release testosterone steadily over three to six months. The FDA-approved dose range is 150–450 mg per insertion (Testopel FDA label). No daily compliance burden, no peaks and troughs, but the placement is irreversible in the short term — if the dose isn't right, you wait it out. There's also a small risk of pellet extrusion or site infection.

Other Formulations

• Androderm — a transdermal patch worn on the skin
• Natesto — a nasal testosterone gel that doesn't carry secondary transfer risk
• Striant — a buccal system placed against the gum

Each has its own absorption profile and compliance profile. The right choice depends on your lifestyle, your risk tolerance, and your provider's clinical judgment.

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Is Testosterone Replacement Therapy Safe?

For men who meet the diagnostic criteria and don't have contraindications, TRT has an established safety profile — backed by the largest randomized trial ever conducted on the question. Known risks exist and require active monitoring, but for carefully selected patients, the evidence is reassuring.

Cardiovascular Safety

The TRAVERSE trial — a 5,204-man, placebo-controlled RCT conducted at 316 sites across the US — is the largest cardiovascular safety study on TRT ever completed. Men aged 45–80 with confirmed low testosterone and cardiovascular disease or high CV risk were randomized to 1.62% topical testosterone gel or placebo. The trial was specifically powered to test cardiovascular non-inferiority for major adverse cardiovascular events (MACE), and it found no increased risk (Bhasin et al., 2023).

The longstanding concern about CV harm in men with existing heart disease was directly tested at scale — and not confirmed. Non-inferiority for MACE. That's the result.

Prostate Safety

The same TRAVERSE trial examined prostate safety. Men with a PSA above 3.0 ng/mL were excluded before enrollment. Among the eligible population, TRT did not increase the rate of high-grade prostate cancer (Bhasin et al., 2023). This does not mean TRT is safe for men with existing prostate cancer — it is contraindicated in that setting. The TRAVERSE data applies to men without known prostate carcinoma who meet the PSA exclusion criteria.

Mental Health and Mood

Among the 5,204 men in TRAVERSE, 50.8% had clinically significant depressive symptoms at baseline. TRT was associated with meaningful improvement in those symptoms over the treatment period (Bhasin et al., 2024). This is consistent with what many men report anecdotally — mood, motivation, and sense of well-being often shift when testosterone is restored to a normal physiological range.

Known Risks That Require Monitoring

• Polycythemia — TRT raises hematocrit. If it rises above 54%, treatment is typically paused. This is why regular hemoglobin/hematocrit monitoring is part of any well-run protocol.
• Venous thromboembolism (VTE) — postmarketing reports have associated TRT with DVT and pulmonary embolism. The FDA label carries this warning. It's a real signal that requires attention in men with prior VTE or clotting disorders.
• Infertility — exogenous testosterone suppresses LH and FSH via negative feedback on the hypothalamic-pituitary axis, which causes oligospermia or azoospermia. This is a direct, predictable effect that needs to be discussed before starting treatment (Heidelbaugh & Belakovskiy, 2024).

FDA FAERS data documents 51,926 adverse event reports associated with testosterone products, including serious cardiovascular events and strokes. These are real-world signals from a large treatment population, not clinical trial findings — but they matter.

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What If You Want to Preserve Fertility?

TRT suppresses sperm production in most men — sometimes to zero — because exogenous testosterone shuts down the LH and FSH signals that drive both testosterone production and spermatogenesis. This effect needs to be discussed before the first injection. For men who haven't completed their family, two alternatives preserve fertility while treating the testosterone deficiency: clomiphene citrate and hCG. Both are off-label but standard of care in this setting (Ide et al., 2020).

Clomiphene citrate (including the enclomiphene isomer) is a selective estrogen receptor modulator (SERM). It blocks estrogen receptors at the hypothalamus and pituitary, which makes the brain think estrogen is low — and increases GnRH, LH, and FSH output as a result. Testosterone rises without suppressing the axis. Sperm production is preserved or improved (Scovell & Khera, 2018).

hCG mimics LH directly. Injected subcutaneously, it stimulates Leydig cells to produce testosterone and maintains testicular volume and spermatogenesis. It's often used alone or alongside low-dose TRT in men who want to stay fertile while managing symptoms.

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How Long Does TRT Take to Work?

TRT produces its effects in stages: libido and energy typically improve within 3–6 weeks, mood changes follow over weeks to months, and muscle and bone changes take 3–24 months to fully develop (Gallegos, 2024). Most men notice something within the first two months — but the full picture takes longer.

• Libido and energy — often the first things to improve, typically within 3–6 weeks
• Mood and cognitive function — may start shifting around the same time, though some men need 3–6 months to notice consistent change
• Muscle mass and body composition — meaningfully changed at 3–6 months of consistent treatment with appropriate diet and training
• Bone density — takes 12–24 months to show meaningful improvement (Tenuta et al., 2025)

The biggest mistake men make is quitting TRT within the first few weeks because they don't feel dramatically different. The effects are real, but they're cumulative. They build on each other over time.

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Does Lifestyle Matter When You're on TRT?

It matters both before and during treatment. In men with functional hypogonadism — low testosterone driven primarily by obesity, metabolic dysfunction, poor sleep, or medication effects — lifestyle changes can normalize testosterone without any pharmacological intervention at all.

In obese men with hypogonadism, significant weight loss is associated with meaningful testosterone recovery. The mechanism is straightforward: adipose tissue converts testosterone to estrogen via aromatase. More fat tissue means more conversion, and the feedback from elevated estrogen further suppresses LH output. Less fat means less conversion and better signaling (Tsutsumi & Tsuchiya, 2025).

In men with clinical hypogonadism who are already on TRT, lifestyle matters differently. Viola et al. (2025) showed that combining TRT with structured lifestyle therapy improved skeletal muscle glycolysis in older men with obesity and hypogonadism — a direct metabolic benefit that neither intervention achieved as effectively alone. The two work better together.

Sleep, alcohol use, and chronic stress also affect testosterone production through cortisol and other mechanisms. These aren't replacements for TRT in men with true hypogonadism — but they're worth addressing regardless of whether you're on treatment.

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Does TRT Treat the Mental Health Effects of Low T?

When depression is a symptom of hypogonadism rather than a standalone condition, treating the testosterone deficiency often improves mood — and the TRAVERSE data makes this concrete. Among the 5,204 men enrolled, 50.8% had clinically significant depressive symptoms at baseline. Treatment with TRT was associated with meaningful reductions in those symptoms (Bhasin et al., 2024).

A real-world case report from 2026 documented a man whose major depressive disorder, resistant to multiple medications, improved significantly after TRT was initiated for late-onset hypogonadism symptoms — a finding consistent with the biological mechanism (Ichino et al., 2026).

TRT doesn't cure depression in men with normal testosterone. But when depression is a symptom of hypogonadism, restoring physiological T levels addresses the root — and the mood follows. If low testosterone and mood problems are both present, they're almost certainly connected.

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Getting Started: What the Process Actually Looks Like

A proper TRT evaluation follows a defined sequence — and any provider skipping steps is cutting corners that matter. At HEXIS, no protocol starts without a full hormone panel and two qualifying testosterone measurements. Here's what that evaluation includes:

1. Symptom assessment — fatigue, libido, muscle changes, mood, sleep, cognitive function
2. Two morning testosterone measurements on separate days — both below 300 ng/dL to meet the diagnostic threshold
3. LH and FSH — to determine whether hypogonadism is primary or secondary
4. PSA and prostate evaluation — to rule out contraindications before starting
5. Hematocrit and hemoglobin baseline — because TRT will raise these
6. Discussion of fertility goals — because TRT will affect them

Ongoing monitoring includes testosterone levels (targeting mid-normal range), hematocrit (hold if Hct >54%), PSA checks, and blood pressure. A protocol without monitoring is not a protocol — it's a prescription.

If you're in the earlier stages of thinking about this — comparing it to testosterone boosters or trying to understand what low T symptoms actually are — the evidence on those questions is worth reading before making any decisions. For men who are further along and ready to look at lab-driven options, HEXIS protocols start with a full hormone panel before anything else gets discussed.

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Frequently Asked Questions

Is TRT approved by the FDA?

Testosterone replacement therapy is FDA-approved for men with primary hypogonadism (due to conditions like Klinefelter syndrome or testicular injury) and secondary hypogonadism (caused by insufficient signaling from the brain). It is not established as a treatment for age-related testosterone decline in otherwise healthy men — that remains off-label use.

Will TRT make me infertile?

TRT suppresses LH and FSH, which reduces or stops sperm production in most men. For men who want to preserve fertility, alternatives like clomiphene citrate or hCG are worth discussing with your provider before starting testosterone. Fertility recovery after stopping TRT is possible but not guaranteed, and the timeline varies.

What is the diagnostic threshold for low testosterone?

Clinical guidelines and the FDA require two separate morning testosterone measurements below 300 ng/dL, along with symptoms consistent with hypogonadism. A single low reading is not sufficient — testosterone varies day to day, which is why the two-measurement requirement exists.

How is TRT different from testosterone boosters?

TRT is a medical treatment using actual testosterone — prescribed, dosed, and monitored by a provider. Testosterone boosters are supplements, typically zinc, vitamin D, or herbal extracts, that may support testosterone production at the margins in men who are deficient in those nutrients. They are not equivalent to TRT and are not appropriate for men with clinical hypogonadism.

Can you stop TRT once you start?

Yes, but your natural testosterone production may be suppressed for weeks to months after stopping — sometimes longer. Some men return to their pre-treatment baseline. Others don't, particularly if they were already in the lower range before starting. This is a real consideration before initiating therapy, especially for younger men.

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The Bottom Line

Low testosterone is real, it's measurable, and for men with confirmed hypogonadism, treatment is available and well-studied. The TRAVERSE trial gave us the largest randomized safety data we've ever had on TRT — 5,204 men, cardiovascular non-inferiority confirmed, prostate safety established for the eligible population (Bhasin et al., 2023).

But TRT is not a shortcut, and it's not for everyone. It requires proper diagnosis, the right formulation for your situation, honest discussion about fertility, and ongoing monitoring. When those things are in place, the evidence is clear: for men with true hypogonadism, testosterone therapy works.

If this is where you are and you want to actually look at your numbers, Schedule a consultation — we start with labs, not assumptions.

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Reviewed by the HEXIS Health Medical Team — licensed physicians and advanced practice providers specializing in hormone optimization, men's health, and metabolic medicine. HEXIS protocols are built on lab-verified baselines and ongoing monitoring, not one-size-fits-all prescribing.

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