Persistent fatigue, brain fog, slower recovery after workouts, and stalled progress in the gym are some of the most common reasons men start searching for "low T." They are also symptoms with many possible causes, which is why the best testosterone conversations start with data instead of assumptions.

This guide walks through what clinical research says about testosterone therapy and enclomiphene, what the major trials did and did not show, and how a physician-guided evaluation works at Calibrate IV.

What "low testosterone" means clinically

The Endocrine Society's 2018 clinical practice guideline recommends diagnosing hypogonadism only in men who have symptoms and signs of testosterone deficiency and unequivocally and consistently low testosterone concentrations. It also recommends confirming the result with a repeat morning fasting measurement, then looking for the cause of the deficiency ^[1].

That last step matters. Hypogonadism is generally described in two forms. In primary hypogonadism, the testes are not producing enough testosterone despite normal signaling from the brain. In secondary hypogonadism, the signaling hormones from the pituitary (LH and FSH) are low or inappropriately normal. Which type a man has can influence which treatment options are appropriate.

Symptoms worth discussing with a provider

• Persistent fatigue despite adequate sleep
• Difficulty focusing or reduced mental clarity
• Lower libido or changes in sexual function
• Difficulty building or maintaining muscle
• Slower recovery after exercise

None of these symptoms is specific to testosterone. Sleep, stress, nutrition, medications, and other medical conditions can produce the same picture, which is why bloodwork and a clinical review come before any treatment decision.

What randomized trials show testosterone therapy may support

Sexual function, mood, and energy

The Testosterone Trials (Snyder et al., New England Journal of Medicine, 2016) are a set of randomized, double-blind, placebo-controlled trials in 790 men aged 65 or older with testosterone below 275 ng/dL and symptoms of deficiency. After one year of testosterone gel, men in the treatment group had significantly greater sexual activity, sexual desire, and erectile function than those on placebo. They also reported slightly better mood and fewer depressive symptoms ^[2].

Energy told a more nuanced story. Testosterone did not produce a significant benefit on the trial's fatigue-based vitality measure, even though more men in the treatment group reported feeling that their energy had improved. The investigators characterized the overall benefits as moderate ^[2]. Results from older men with clearly low levels should not be assumed to apply to everyone.

Body composition

In a randomized, placebo-controlled trial of men with type 2 diabetes and hypogonadotropic hypogonadism (Dhindsa et al., Diabetes Care, 2016), 24 weeks of intramuscular testosterone was associated with a 3.4 kg increase in lean mass and a 3.3 kg decrease in subcutaneous fat compared with placebo. Visceral and liver fat did not change significantly ^[3]. This was a specific population, and the results should be read as exactly that.

What we know about safety

Cardiovascular safety: the TRAVERSE trial

TRAVERSE (Lincoff et al., New England Journal of Medicine, 2023) is a randomized, double-blind, placebo-controlled noninferiority trial that enrolled 5,246 men aged 45 to 80 with symptoms of hypogonadism, testosterone below 300 ng/dL, and either existing cardiovascular disease or elevated cardiovascular risk. Testosterone gel was noninferior to placebo for major adverse cardiac events (7.0% versus 7.3%) ^[4].

The same trial also reported higher rates of atrial fibrillation, acute kidney injury, and pulmonary embolism in the testosterone group ^[4]. Prostate cancer was uncommon and similar between groups (12 cases versus 11) ^[4]. Two caveats are worth knowing: the trial used a daily gel rather than injections, and it was funded by a consortium of testosterone manufacturers. The senior author has said the findings should not justify widespread prescribing to large numbers of men.

What the FDA changed in 2025

In February 2025, the FDA announced class-wide labeling changes for testosterone products. It added the TRAVERSE results to labels, removed boxed-warning language about increased cardiovascular risk, kept the "Limitation of Use" language for age-related hypogonadism, and required blood pressure information and warnings after postmarket studies showed testosterone products can raise blood pressure ^[5]. In plain terms, testosterone products are not approved for low testosterone due to aging alone, and blood pressure is part of the monitoring conversation.

Monitoring, fertility, and who may not be a candidate

The Endocrine Society guideline recommends a standardized monitoring plan during the first year of therapy that includes symptoms, side effects, serum testosterone, hematocrit, and prostate cancer risk. Hematocrit is generally checked at baseline and again within the first three to six months, with therapy paused or adjusted if it rises too high ^[1].

The guideline recommends against starting testosterone therapy in men who are planning fertility in the near term, and also in men with breast or prostate cancer, a palpable prostate nodule, elevated PSA without further evaluation, elevated hematocrit, untreated severe sleep apnea, severe urinary symptoms, uncontrolled heart failure, a heart attack or stroke within the past six months, or thrombophilia ^[1]. Testosterone replacement can suppress the brain signals that drive sperm production, which is why fertility goals belong in the very first conversation.

Two approaches: injectable testosterone and oral enclomiphene

Injectable testosterone cypionate

Testosterone cypionate is an injectable form of testosterone replacement dosed on a scheduled basis, typically weekly, under clinical oversight with lab monitoring. Much of the strongest published evidence on testosterone therapy, including TRAVERSE and the Testosterone Trials, used topical gel, so conclusions about outcomes and risks are drawn across formulations and should be discussed with your provider.

Oral enclomiphene

Enclomiphene is an oral selective estrogen receptor modulator. Rather than supplying testosterone, it acts at the brain to raise LH and FSH, which stimulates the body's own testosterone production. That approach is studied specifically in secondary hypogonadism.

In a randomized phase II trial (Wiehle et al., Fertility and Sterility, 2014), enclomiphene raised morning testosterone to levels similar to topical testosterone gel while conserving sperm counts ^[6]. Two randomized, double-blind phase III trials in overweight men aged 18 to 60 with secondary hypogonadism (Kim et al., BJU International) compared enclomiphene with testosterone gel over 16 weeks. Enclomiphene raised testosterone, LH, and FSH and kept sperm concentrations in the normal range, while sperm production fell markedly in the gel group ^[7].

Important context: these trials were short, and long-term safety and effectiveness data are limited. Enclomiphene is not FDA-approved for any indication and is available only by prescription through compounding pharmacies ^[8]. Whether it is appropriate for a given man is a decision for a licensed provider after reviewing his labs.

How physician-guided care works at Calibrate IV

1. Intake and labs. A comprehensive blood panel establishes your baseline hormone levels.
2. Provider review. A one-on-one consultation reviews your symptoms, health history, goals, and candidacy, including any fertility plans.
3. Custom plan. If therapy is appropriate, your provider prescribes a plan matched to your labs and your physiology.
4. Ongoing monitoring. Regular check-ins and follow-up labs guide dosing adjustments and safety review.

Every protocol is overseen by licensed medical professionals and sourced through US pharmacies. Not everyone who inquires will be a candidate, and that is the point of the evaluation.

Frequently asked questions

Does feeling tired mean I have low testosterone?
Not necessarily. Fatigue has many possible causes. Guidelines call for consistent symptoms plus repeated low morning testosterone results before a diagnosis is made ^[1].

Will testosterone therapy affect my fertility?
It can. Testosterone therapy may reduce sperm production, and the Endocrine Society recommends against starting it in men planning fertility soon ^[1]. Enclomiphene maintained sperm concentrations in the trials described above, though those were short-term studies in men with secondary hypogonadism ^[7].

Is testosterone therapy safe for my heart?
TRAVERSE found no increase in major adverse cardiac events versus placebo in men with elevated cardiovascular risk, along with higher rates of atrial fibrillation, acute kidney injury, and pulmonary embolism ^[4]. Your provider should review your cardiovascular history and blood pressure before and during any treatment ^[5].

What is the difference between injectable testosterone and enclomiphene?
Injectable testosterone supplies testosterone directly. Enclomiphene prompts your body to make more of its own and has been studied in secondary hypogonadism. Which one, if either, fits depends on your labs, health history, and goals.

Take the first step

If you are noticing the symptoms above, the most useful next step is data. Learn more about our testosterone therapy options or book a consult with a Calibrate IV provider. You can also reach our concierge team at 1-844-416-2546 or concierge@calibrateiv.com.

This article is for educational purposes and is not medical advice. Testosterone therapy and enclomiphene require a prescription, and candidacy is determined by a licensed provider after a medical evaluation and lab work. Individual results vary. Regulatory information is current as of September 2026.

References

1. Bhasin S, Brito JP, Cunningham GR, et al. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2018;103(5):1715–1744. PMID 29562364. (Clinical practice guideline)
2. Snyder PJ, Bhasin S, Cunningham GR, et al. Effects of Testosterone Treatment in Older Men. N Engl J Med. 2016;374(7):611–624. (Randomized controlled trial, human)
3. Dhindsa S, Ghanim H, Batra M, et al. Insulin Resistance and Inflammation in Hypogonadotropic Hypogonadism and Their Reduction After Testosterone Replacement in Men With Type 2 Diabetes. Diabetes Care. 2016;39(1):82–91. PMID 26622051. (Randomized controlled trial, human)
4. Lincoff AM, Bhasin S, Flevaris P, et al. Cardiovascular Safety of Testosterone-Replacement Therapy. N Engl J Med. 2023;389(2):107–117. PMID 37326322. (Randomized controlled trial, human)
5. US Food and Drug Administration. FDA issues class-wide labeling changes for testosterone products. February 28, 2025. (Regulatory announcement)
6. Wiehle RD, Fontenot GK, Wike J, et al. Enclomiphene citrate stimulates testosterone production while preventing oligospermia: a randomized phase II clinical trial comparing topical testosterone. Fertil Steril. 2014;102(3):720–727. PMID 25044085. (Randomized phase II trial, human)
7. Kim ED, McCullough A, Kaminetsky J. Oral enclomiphene citrate raises testosterone and preserves sperm counts in obese hypogonadal men, unlike topical testosterone: restoration instead of replacement. BJU Int. 117(4):677–685. PMID 26496621. (Two randomized phase III trials, human)
8. US Food and Drug Administration. Pharmacy Compounding Advisory Committee meeting, June 8, 2022 (enclomiphene citrate and the 503A Bulks List); and current compounding pharmacy regulatory status. (Regulatory)