Testosterone and Heart Health: What Every Man Needs to Know

The Fear That Keeps Men From Getting Treatment

You have been reading about testosterone replacement therapy. Maybe your levels came back low. Maybe you have been dealing with a disappearing sex drive, muscle loss despite training, or a general sense that your body stopped cooperating sometime after 40. You are ready to do something about it — and then you Google "TRT and heart risk" and everything grinds to a halt.

Headlines about heart attacks. Vague warnings from your primary care doctor. A friend who told you his physician refused to prescribe testosterone because "it is bad for your heart." The fear is real, and it has kept countless men with legitimate hormonal deficiencies from getting treatment they need.

Here is the truth: the relationship between testosterone and cardiovascular health is one of the most studied and most misunderstood topics in men's medicine. For over a decade, outdated concerns dominated the conversation. But the science has caught up. And the largest, most rigorous clinical trial ever conducted on this question — the TRAVERSE trial — has fundamentally changed what we know.

This article breaks down the evidence. Not opinions, not anecdotes — the actual data from randomized controlled trials, meta-analyses, and large-scale observational studies. By the end, you will understand what testosterone does to your cardiovascular system, what the real risks are, and what makes the difference between safe treatment and reckless prescribing.

Where the Cardiovascular Concern Came From

The fear about testosterone and heart health did not appear from nowhere. It came from a specific sequence of events that, in hindsight, generated more confusion than clarity.

The 2010 TOM Trial

In 2010, a small trial called TOM (Testosterone in Older Men with Mobility Limitations) was stopped early because men in the testosterone group had more cardiovascular events than the placebo group. The study included 209 older men (average age 74) with significant mobility limitations and multiple comorbidities. The testosterone doses used were notably higher than standard clinical practice, and the trial was not designed or powered to evaluate cardiovascular outcomes.

Despite its severe limitations — tiny sample size, unusually sick population, supraphysiological dosing in some participants — the TOM trial generated headlines and planted a seed of concern that persisted for over a decade.

The 2013–2014 Observational Studies

Two retrospective observational studies published in 2013 and 2014 reported increased cardiovascular risk with testosterone use. One analyzed VA medical records and the other used insurance claims data. Both had significant methodological problems — including counting prescriptions as proof of treatment (regardless of whether men actually used them), failing to confirm hypogonadism diagnoses, and not adjusting for important confounders.

Multiple subsequent analyses identified errors in these studies, and the authors of the VA study later published a correction. But the damage was done. Media coverage was extensive, and the FDA responded.

The 2015 FDA Label Change

In 2015, the FDA required testosterone product labels to include a general warning about possible cardiovascular risk. Critically, the FDA did not conclude that testosterone causes heart attacks or strokes. It added the warning based on the observational data and stated that the evidence was "inconclusive" — essentially calling for the definitive trial that would settle the question.

That trial arrived in 2023.

The TRAVERSE Trial: The Study That Changed Everything

The TRAVERSE (Testosterone Replacement therapy for Assessment of long-term Vascular Events and efficacy ResponSE in hypogonadal men) trial was specifically designed to answer the cardiovascular safety question once and for all. Published in the New England Journal of Medicine in July 2023, it remains the gold standard on this topic.

Study Design

TRAVERSE was a randomized, double-blind, placebo-controlled, noninferiority trial — the highest level of clinical evidence. Here is what that means in practice:

• 5,246 men ages 45 to 80 with documented hypogonadism (two separate testosterone measurements below 300 ng/dL)
• All participants had either preexisting cardiovascular disease or were at high risk for it
• Men were randomly assigned to receive either daily transdermal testosterone gel or placebo
• Neither the participants nor the researchers knew who was getting testosterone
• Mean treatment duration was approximately 22 months, with an average follow-up of 33 months
• Testosterone doses were adjusted to maintain levels between 350 and 750 ng/dL — standard therapeutic range

The Primary Results

The primary endpoint was a composite of major adverse cardiovascular events (MACE): cardiovascular death, nonfatal heart attack, or nonfatal stroke.

Outcome	Testosterone Group	Placebo Group	Difference
MACE (primary endpoint)	7.0%	7.3%	No significant difference
Cardiovascular death	2.0%	1.9%	No significant difference
Nonfatal heart attack	3.5%	3.9%	No significant difference
Nonfatal stroke	2.0%	1.9%	No significant difference

The headline finding: testosterone replacement therapy did not increase the risk of heart attack, stroke, or cardiovascular death compared with placebo — even in a population specifically selected for high cardiovascular risk.

Dr. Michael Lincoff, the co-principal investigator from the Cleveland Clinic, stated that "these findings provide reassurance about the cardiovascular safety of testosterone therapy over the typical duration of treatment in men in whom it is indicated."

What the Meta-Analyses Confirm

TRAVERSE did not arrive in a vacuum. A 2024 meta-analysis published in Progress in Cardiovascular Diseases pooled data from 30 randomized controlled trials with a combined total of 11,502 patients. The conclusions were unequivocal:

• Any cardiovascular event: No increased risk (OR 1.12, 95% CI 0.77–1.62, p = 0.55)
• Stroke: No increased risk (OR 1.01, 95% CI 0.68–1.51, p = 0.94)
• Heart attack: No increased risk (OR 1.05, 95% CI 0.76–1.45, p = 0.77)
• All-cause mortality: No increased risk (OR 0.94, 95% CI 0.76–1.17, p = 0.57)
• Cardiovascular mortality: No increased risk (OR 0.87, 95% CI 0.65–1.15, p = 0.31)

Every single cardiovascular endpoint showed no increased risk with testosterone replacement therapy compared to placebo. And the point estimates for all-cause mortality and cardiovascular mortality actually trended in favor of testosterone — though neither reached statistical significance.

A separate systematic review spanning 25 years of prospective cohort data (51 studies, published 2024) went further, finding an inverse association between testosterone therapy and cardiovascular disease risk — meaning men who received treatment tended to have better cardiovascular outcomes than those who did not.

Low Testosterone and Heart Risk: The Other Side of the Equation

Here is what often gets lost in the fear-driven conversation: low testosterone itself is a cardiovascular risk factor. The question is not just whether treating it might cause harm — it is whether leaving it untreated causes harm. And the data strongly suggests it does.

A 2025 study published in PMC analyzing male patients with cardiovascular disease found that low serum testosterone was associated with a 48% increased risk of all-cause mortality (HR 1.48, 95% CI 1.08–2.02). This held after adjusting for age, BMI, diabetes, hypertension, and other standard cardiovascular risk factors.

The association between low testosterone and cardiovascular risk operates through multiple pathways:

Factor	How Low Testosterone Increases Risk
Visceral fat	Low T promotes abdominal fat storage, which drives inflammation and insulin resistance
Insulin resistance	Testosterone deficiency worsens metabolic syndrome and type 2 diabetes risk
Lipid profile	Low T is associated with higher triglycerides and lower HDL cholesterol
Arterial stiffness	Testosterone has vasodilatory effects; deficiency increases vascular resistance
Inflammation	Low T is associated with elevated inflammatory markers (CRP, IL-6)
Endothelial function	Testosterone supports nitric oxide production, which is essential for healthy blood vessel function

A Swiss prospective cohort study found that approximately 40% of men with acute coronary syndromes had low testosterone — and those low levels were associated with significantly higher one-year mortality. A Greek cohort showed low testosterone predicted five-year cardiovascular death in men with stable coronary heart disease.

The irony is hard to miss: the very condition that doctors feared treating has itself been shown to increase cardiovascular risk. Leaving clinically low testosterone untreated is not a neutral, risk-free decision. It carries its own consequences.

What TRT Actually Does to Your Cardiovascular System

Testosterone does not just float around doing nothing to your blood vessels and heart. It has direct and indirect effects on multiple cardiovascular parameters. Understanding these helps explain both the historical concern and the reassuring evidence from modern trials.

Positive Effects

• Vasodilation: Testosterone promotes nitric oxide production in endothelial cells, relaxing blood vessels and improving blood flow. This is the same pathway targeted by some blood pressure medications
• Body composition: TRT consistently reduces visceral fat and increases lean mass — both of which improve metabolic and cardiovascular risk profiles. Men who cannot lose weight despite effort often see a shift after testosterone levels normalize
• Insulin sensitivity: Restoring testosterone levels improves glucose metabolism and reduces insulin resistance, lowering the risk of the metabolic syndrome cascade that leads to cardiovascular disease
• Inflammation: Testosterone replacement has been shown to reduce markers of systemic inflammation (CRP, TNF-alpha), which are independent risk factors for cardiovascular events
• Exercise capacity: Improved energy, motivation, and muscle function from TRT allows men to exercise more effectively — one of the most potent cardiovascular risk reducers available

Parameters to Watch

• Hematocrit: Testosterone stimulates red blood cell production, which can thicken the blood. This is manageable but requires monitoring (see next section)
• Lipids: TRT can modestly reduce HDL cholesterol, though the clinical significance of this isolated change is debated. Total cardiovascular risk profiles generally improve
• Blood pressure: Some men experience modest blood pressure changes early in treatment. Regular monitoring allows for timely management
• Estradiol: Testosterone converts to estradiol via aromatase. Excess estradiol can contribute to fluid retention and other issues. This is why estradiol management on TRT is part of responsible protocols

The Hematocrit Factor: The One Risk You Need to Understand

If there is one cardiovascular-adjacent risk from TRT that genuinely requires attention, it is hematocrit — the percentage of your blood volume made up of red blood cells.

Testosterone stimulates erythropoiesis — the production of new red blood cells. In healthy amounts, this is beneficial: it improves oxygen delivery, exercise capacity, and energy. But if hematocrit climbs too high (a condition called polycythemia), blood becomes thicker and more viscous, increasing the risk of blood clots, stroke, and other thromboembolic events.

A 2022 study published in the Journal of Urology quantified this risk precisely:

Hematocrit Status on TRT	MACE/VTE Rate (Year 1)	Odds Ratio
Normal hematocrit (<52%)	3.9%	Reference
Polycythemia (≥52%)	5.2%	1.35 (p < 0.001)

The critical takeaway: TRT itself, in the absence of polycythemia, did not increase cardiovascular or thromboembolic risk. But developing polycythemia while on TRT was an independent risk factor — increasing the risk of MACE and venous thromboembolism by 35% in the first year of therapy.

This is why hematocrit monitoring is non-negotiable on TRT. Not optional. Not "check it if you feel off." Regular blood work, including hematocrit, is the difference between safe testosterone therapy and unnecessary risk.

Atrial Fibrillation and Blood Clots: Important Nuances From TRAVERSE

While TRAVERSE showed no increase in MACE, it did identify two secondary findings that deserve honest discussion:

Atrial Fibrillation (AFib)

Men in the testosterone group had a slightly higher incidence of atrial fibrillation — an irregular heart rhythm that can increase the risk of stroke and heart failure. The absolute increase was small, and AFib is relatively common in older men with cardiovascular risk factors regardless of testosterone status. But it means men with a history of AFib or strong risk factors for it should discuss this with their provider before starting TRT.

Pulmonary Embolism

The testosterone group also showed a slightly higher rate of pulmonary embolism — a blood clot that travels to the lung arteries. Again, the absolute numbers were small, but the finding is biologically plausible given testosterone's effect on red blood cell production and the hematocrit-mediated clotting risk discussed above.

These findings do not undermine the overall cardiovascular safety signal from TRAVERSE. They contextualize it. Testosterone therapy is safe for your heart in the sense that it does not cause heart attacks or strokes. But it is not risk-free in every dimension, and specific risks (hematocrit elevation, AFib in predisposed men, thromboembolic events) need to be managed through proper monitoring and clinical oversight.

This is exactly why the decision to start TRT should be made with a provider who understands these nuances — not ordered from an unscrupulous online vendor who ships testosterone without follow-up.

Who Should Be Cautious

The TRAVERSE results are reassuring, but they apply specifically to men with confirmed hypogonadism receiving medically supervised, guideline-consistent testosterone replacement. They do not give a green light to every man who wants to use testosterone for any reason.

Extra caution is warranted for men who:

• Do not have confirmed low testosterone — supraphysiological testosterone use (bodybuilding doses) carries entirely different risks and was not evaluated in TRAVERSE
• Have a history of polycythemia or elevated hematocrit — these men may be more prone to hematocrit-driven complications
• Have active or recent venous thromboembolism — recent DVT or PE may make testosterone's blood-thickening effects more dangerous
• Have untreated severe sleep apnea — sleep apnea itself raises hematocrit, and adding testosterone can compound the effect. Learn about the testosterone and sleep apnea relationship
• Have uncontrolled heart failure — fluid retention from testosterone could worsen symptoms
• Have a history of atrial fibrillation — the TRAVERSE signal warrants a discussion with your cardiologist

None of these are absolute contraindications in most cases. They are reasons for closer monitoring, cautious dosing, and collaboration between your TRT provider and any other specialists managing your cardiovascular health. Men over 50 considering testosterone therapy should have a particularly thorough baseline cardiovascular assessment.

Why Monitoring Makes All the Difference

The gap between "TRT is safe" and "TRT is safe for you" is bridged by one thing: monitoring. Every major study that has demonstrated cardiovascular safety of testosterone therapy — TRAVERSE included — maintained strict monitoring protocols. Levels were checked. Doses were adjusted. Hematocrit was tracked.

At a minimum, men on TRT should have the following monitored on a regular schedule:

Marker	Why It Matters	Frequency
Total and free testosterone	Ensures levels stay in the therapeutic range (350–750 ng/dL in TRAVERSE)	Every 3–6 months
Hematocrit / CBC	Catches polycythemia before it creates clotting risk	Every 3–6 months
Estradiol	Monitors aromatization; excess estradiol causes fluid retention and other issues	Every 3–6 months
Lipid panel	Tracks HDL, LDL, triglycerides for cardiovascular risk assessment	Every 6–12 months
PSA	Monitors prostate health markers	Annually (or per provider)
Fasting glucose / HbA1c	Tracks metabolic improvements and diabetes risk	Every 6–12 months
Blood pressure	Monitors for fluid retention or vascular changes	Every visit

This is not busywork. It is what separates medically supervised TRT — the kind studied in TRAVERSE and shown to be safe — from unmonitored testosterone use that carries genuine risk. When you read about adverse events linked to testosterone, they almost always involve either unsupervised use, supraphysiological doses, or complete absence of follow-up blood work.

At Heyday, every TRT patient receives ongoing monitoring as part of their protocol. Blood panels are shipped to your door, results are reviewed by licensed providers, and your treatment is adjusted based on real data — not guesswork. This is how testosterone therapy should work. (See the TRT timeline: what to expect week by week.)

The Bottom Line

The cardiovascular safety question around testosterone has been definitively addressed by modern evidence. The TRAVERSE trial — the largest, most rigorous randomized controlled trial ever conducted on this topic — showed that medically supervised TRT does not increase the risk of heart attack, stroke, or cardiovascular death. A 2024 meta-analysis of 30 RCTs with over 11,500 patients confirmed the same conclusion across every cardiovascular endpoint.

At the same time, leaving low testosterone untreated is not a risk-free choice either. Low T is independently associated with increased visceral fat, insulin resistance, worsened mood, metabolic syndrome, and — yes — increased cardiovascular mortality.

The real risk with TRT is not your heart. It is unmonitored treatment. Hematocrit that nobody checks. Doses that nobody adjusts. Cortisol and metabolic factors that nobody evaluates. The evidence is clear: when TRT is prescribed for confirmed hypogonadism and monitored properly, it is cardiovascularly safe.

If you have been avoiding treatment because of an outdated fear — or if your doctor refused to discuss TRT based on decade-old headlines rather than current evidence — it is worth revisiting the conversation. Your heart is important. So is having the facts.