Varicocele: The Most Common Fixable Cause of Low Testosterone

He noticed it in his twenties. A dull ache in the left testicle after a long day standing, and a texture he described to his GP as a bag of worms. He was told it was harmless and common, which was true, and that was the end of it.

Nineteen years later he is being investigated for low testosterone and a poor sperm count. Nobody has connected the two.

Varicocele is present in roughly 15 per cent of men. It is the most common surgically reversible cause of male infertility. And its relationship with testosterone is real, more nuanced than either the clinics or the forums suggest, and worth understanding before anyone offers you a hormone.

What it is

The veins draining your testicles form a network called the pampiniform plexus. In a varicocele, the valves in those veins fail and blood pools rather than draining properly, so the veins dilate.

It occurs on the left in the large majority of cases, because of how the left testicular vein joins the renal vein at a right angle rather than draining smoothly.

The description men use is consistent: a bag of worms, more obvious when standing, less so lying down. Larger ones are visible; smaller ones are found only on examination.

Why it affects testosterone

The pampiniform plexus does more than drain blood. It runs a counter-current cooling system, keeping the testicles a couple of degrees below body temperature, which is what sperm production requires.

When blood pools, that cooling fails. Three consequences follow.

Heat. Scrotal temperature rises, and both sperm production and testosterone synthesis are temperature-sensitive.

Oxidative stress. Stagnant blood generates reactive oxygen species that damage both sperm and the Leydig cells producing testosterone.

Leydig cell damage. Animal work shows Leydig cell death and reduced testosterone synthesis in surgically induced varicocele compared with sham operations, with the effect measurable within weeks.

So the mechanism is not speculative. What is debated is how much it matters in any individual man.

What the numbers actually show

Here is where honest reading separates from the marketing, because the evidence points in two directions depending on who is being treated.

For fertility, the case is strong. Varicocele is found in up to 35 per cent of men presenting with primary infertility and up to 80 per cent with secondary infertility. Repair improves semen parameters in around 70 per cent of infertile men, and roughly 40 per cent achieve a pregnancy as a result.

For testosterone, it depends on where you start. A meta-analysis of nine studies covering 814 patients found testosterone rose by around 97.5 ng/dL after repair. Another meta-analysis across seven studies and 712 men found a more modest average improvement of 34.3 ng/dL.

Then the finding that reconciles them. In that second analysis, when researchers looked specifically at men who were hypogonadal before surgery, testosterone rose by 105.65 ng/dL compared with untreated controls.

Read that carefully, because it is the practical point. Repairing a varicocele in a man with normal testosterone does very little. Repairing one in a man whose testosterone is already low does considerably more.

And some studies found no significant change at all, particularly in men with normal baseline levels. A 2026 systematic review concluded that repair significantly improves both testosterone and testicular volume, but the size of that benefit clearly depends on the starting point.

When it is worth investigating

Most varicoceles need nothing. The question is which ones do.

You have low testosterone and a varicocele. This is the combination where the evidence is strongest, and it is the one most often left unexplored because the varicocele was dismissed years earlier as harmless.

You are struggling to conceive. The clearest indication, and the one urologists act on most readily. TRT and fertility covers why this matters before starting testosterone rather than after.

Pain that interferes with your day. A dull ache, worse when standing or after exercise, better lying down.

A smaller testicle on the affected side. This suggests the varicocele has caused measurable damage, and in adolescents it is a recognised reason to intervene.

A varicocele that appeared suddenly, particularly on the right side or one that does not reduce when you lie down, needs prompt assessment for a different reason: it can occasionally indicate something obstructing the vein higher up.

What happens at the appointment

Diagnosis is clinical. A urologist examines you standing, and asks you to bear down, which increases pressure and makes smaller varicoceles apparent.

They are graded by size, from those found only on straining to those visible through the skin. Scrotal ultrasound confirms it and measures testicular volume, which is the more useful number.

Alongside that, a proper workup includes two morning testosterone measurements with LH, FSH and SHBG, and a semen analysis if fertility is relevant. The blood test guide covers what to ask for.

Repair, and who it suits

Several approaches exist, and the differences matter.

Microsurgical subinguinal varicocelectomy is generally regarded as the best option. Using a microscope, the surgeon ties off the affected veins while preserving the artery and lymphatics, which is what keeps complication and recurrence rates low.

Laparoscopic repair is an alternative, done higher in the abdomen.

Embolisation is performed by a radiologist through a catheter, blocking the veins from inside. No incision, quicker recovery, and a somewhat higher recurrence rate.

Recovery from microsurgical repair is typically a few days off work and a few weeks before heavy lifting. Semen parameters take around three months to change, because that is how long sperm production takes. Testosterone changes are usually assessed at three to six months.

The decision this actually informs

Here is the part worth taking to an appointment.

A man with low testosterone and a varicocele has two options, and they are not equivalent.

Testosterone replacement treats the symptom. It works, it is usually lifelong, and it shuts down your own production and sperm output while you take it.

Varicocele repair treats a cause. It may raise your own testosterone by around 100 ng/dL if you are hypogonadal, it preserves fertility rather than suppressing it, and it is a single intervention rather than an ongoing prescription.

Repair does not always work, and the improvement may not be enough on its own. But the sequence matters: repair first, reassess at six months, then decide about replacement, is a very different path from starting testosterone and discovering the varicocele later.

An online clinic that prescribes after one blood test will never examine you, and therefore will never find this. Online TRT clinics covers what a proper assessment includes.

The honest summary

Most varicoceles are harmless and need nothing. If yours causes no pain, your testosterone is normal and you are not trying to conceive, leaving it alone is reasonable.

But if you have low testosterone, a varicocele, and nobody has connected them, that is worth a urology opinion before you commit to lifelong replacement. It is the most common fixable cause on the list, and fixing a cause beats replacing an output.

The examination takes two minutes. It just has to happen.

Common questions

Does a varicocele lower testosterone?

It can. Pooled blood impairs the cooling system, raises scrotal temperature and generates oxidative stress, and animal studies show Leydig cell damage. The effect varies considerably between men.

Will surgery raise my testosterone?

It depends on your starting level. Meta-analyses found average rises of 34 to 97 ng/dL, but among men who were hypogonadal beforehand the increase was around 105 ng/dL. Men with normal testosterone see little change.

How common is varicocele?

Around 15 per cent of men. It rises to roughly 35 per cent in men with primary infertility and up to 80 per cent in secondary infertility.

Do I need it repaired?

Not usually. Repair is considered for infertility, low testosterone with a varicocele, pain affecting daily life, or a smaller testicle on the affected side. Most varicoceles need nothing.

Should I try repair before TRT?

If you have both low testosterone and a varicocele, it is worth discussing. Repair treats a cause and preserves fertility, while testosterone treats the symptom and suppresses sperm production. Repair first, reassess at six months, is a reasonable sequence.

Why is it almost always on the left?

Because of the anatomy. The left testicular vein joins the renal vein at a right angle rather than draining smoothly, which raises pressure in the veins below it.

Sources: Li F et al., Effect of varicocelectomy on testosterone: a meta-analysis, Int J Androl 2012, covering nine studies and 814 patients · Effects of varicocele repair on testicular endocrine function: a systematic review and meta-analysis, World J Mens Health 2025 · Oktarina A et al., Effect of varicocelectomy on testicular volume and testosterone hormone in teens and young adults with varicocele: a systematic review and meta-analysis, Adv Urol 2026;3370492 · Clavijo RI, Carrasquillo R, Ramasamy R, Varicoceles: prevalence and pathogenesis in adult men, Fertil Steril 2017;108:364-9 · Educational only, not medical advice.

Keep reading: What causes low testosterone · Will TRT make you infertile · Prolactin: the test that changes the diagnosis · Blood test: what to check · TRT versus natural optimisation · Online TRT clinics