Quick Answer: Yes, some STDs, especially untreated chlamydia, gonorrhea, and syphilis, can cause testicular damage like pain, swelling, or long-term shrinkage, usually due to inflammation or infection of surrounding structures like the epididymis or testicular tissue itself.
This Isn’t Just a Bruise, And Here’s Why
Let’s set the scene. Drew, 26, hadn’t been tested in over a year. He'd had two casual partners since his last relationship ended, always with condoms, except once. A few weeks later, he noticed some swelling near the top of his right testicle. It wasn’t unbearable, just annoying. He figured he sat funny, or maybe it was from lifting at the gym. But the ache persisted. Then, after a month, his testicle actually started to feel smaller. Not pain this time, just weird. Lighter. Not quite right.
He didn't have discharge or sores. But inside his scrotum, something had changed. When he finally went in, the diagnosis surprised him: untreated chlamydia had caused epididymitis, an inflammatory condition that can cause shrinkage or damage if left alone too long.
Drew’s not alone. Roughly 1 in 15 men with untreated chlamydia or gonorrhea can develop complications that affect testicular structures. In rare cases, it leads to what's called testicular atrophy, literal shrinking of the testicle caused by inflammation, scarring, or interrupted blood flow.
Table: STDs That Can Affect Testicle Size or Function
| STD | Can It Affect Testicles? | Mechanism of Damage | Common Symptoms |
|---|---|---|---|
| Chlamydia | Yes | Inflammation of the epididymis (epididymitis) | Swelling, tenderness, ache, sometimes fever |
| Gonorrhea | Yes | Same as chlamydia, often co-infects with it | Painful urination, discharge, scrotal pain |
| Syphilis | Rarely | Late-stage syphilis can cause nerve damage and testicular shrinkage | Chancre sore early; neurological symptoms late |
| HIV | Rarely | Indirect hormonal/testicular effects in late stage | Flu-like illness early; immune suppression later |
| HPV | No | Does not affect internal genital structures | Warts (external), often asymptomatic |
Figure 1. STDs linked to testicular damage through inflammation or indirect impact. Not all cause shrinkage directly, but some do when untreated.
When It’s Shrinking, Not Swelling: Why That Matters
Most guys expect pain or swelling from something serious. Shrinking, though? That throws people off. But testicular atrophy isn’t always dramatic. It can feel like “softening” or “less mass” when held. Some describe it as one ball “floating” higher or feeling hollow. These changes can sneak up and cause delayed concern, sometimes too delayed.
Here’s the physiology in plain English: When infections like chlamydia or gonorrhea reach the epididymis, the coiled tube that helps sperm mature, it can swell, block sperm movement, or cut off blood flow. Over time, the affected testicle can lose volume, firmness, and function.
In one case study from the National Institutes of Health, men with untreated epididymitis showed testicular shrinkage within six weeks. Pain wasn’t always present. But the tissue damage, confirmed on ultrasound, was real.
And this isn't just about size, it’s about fertility, too. Damage to the testicular environment can reduce sperm count, motility, or hormone production. That’s not fear-mongering; it’s medical fact.
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How Fast Can It Happen? Symptom Timelines by STD
| STD | Earliest Symptoms | Timeframe for Testicular Damage (If Untreated) | Can It Be Reversed? |
|---|---|---|---|
| Chlamydia | 7–21 days post-exposure | 4–6 weeks for epididymitis | Sometimes, if caught early |
| Gonorrhea | 2–10 days post-exposure | 2–4 weeks for complications | Yes, with prompt antibiotics |
| Syphilis | 10–90 days (chancre) | Years (late-stage complications) | Damage can be permanent |
Figure 2. Timeline of symptom onset and testicular risk for untreated STDs. Time matters.
Case Study: “I Didn’t Feel Anything Until It Was Too Late”
Marco, 32, hadn’t felt any pain. What brought him in was the size difference, one testicle clearly smaller, no swelling, no soreness. He thought it was aging or just a quirk. But testing revealed an old gonorrhea infection that had silently caused low-grade inflammation in the epididymis and testicle over months. Marco hadn’t known. His only clue? His last hookup had been unprotected. He never had discharge or a burning sensation, just a partner who tested positive and encouraged him to get checked.
“I didn’t even think this was something to get tested for. No pain, no warning. Just one testicle getting smaller over time. That’s how I found out.”
His case wasn’t rare. Many STDs go unnoticed in men, especially if they don’t involve urination or external symptoms. But that doesn’t mean the infection isn’t working its way through internal structures. That’s why we repeat this a lot: no symptoms doesn’t mean no infection.
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When It’s Not an STD: Other Reasons Your Testicles Might Shrink
Let’s pause. Not every change in testicle size is caused by an STD. That’s why getting tested is about clarity, not just infection. Several other conditions can mimic or overlap with STD symptoms. Shrinking, floating, or sore testicles could be caused by unrelated, but equally serious, issues.
Consider testicular torsion. This is a medical emergency where the spermatic cord twists, cutting off blood flow. It causes sudden pain and swelling, but if blood supply is lost for too long, permanent shrinkage can follow. It’s not infectious, but the urgency is real, every hour counts.
Another culprit? Varicoceles. Because of the disturbed blood flow, these dilated veins, which feel like a "bag of worms" inside the scrotum, can eventually result in testicular atrophy. Most don’t hurt, but they do mess with temperature regulation and sperm production.
And then there’s the hormone layer: low testosterone from aging, pituitary disorders, steroid misuse, or chemotherapy can lead to gradual testicle shrinkage. This kind of atrophy is systemic, often paired with low libido, fatigue, or mood changes.
Here’s the bottom line: if one testicle is changing in size, especially if there’s no trauma, you need a full panel that includes STDs, hormones, and possibly an ultrasound. One home test won’t tell you everything, but it’s a crucial first step to rule out silent infections.
What a Normal Testicle Should Feel Like (And Why That Varies)
This is where things get intimate, because most men were never taught how their testicles should actually feel. Firm? Soft? Hanging high or low? The truth is, testicle size varies by individual, by temperature, and even by time of day.
It’s common for one testicle to hang lower (usually the left), and for size to differ slightly. That’s normal anatomy. But when one becomes visibly smaller over weeks or months, or feels lighter, softer, or "emptier", it could be a red flag.
Compare both sides in the shower when relaxed. Look for firmness, fullness, and symmetry. If you notice progressive change, even without pain, it’s worth checking in. Many men catch early symptoms of STDs, torsion, or tumors just by paying attention in those quiet daily moments.
What to Expect From an At-Home STD Test
If you’ve never done it before, testing yourself might feel intimidating. But today’s at-home STD kits are as simple as a nasal swab or urine cup, and many offer reliable lab-grade results for common infections like chlamydia and gonorrhea. Some kits test for 3, 5, or even 11 STDs at once.
The most accurate kits use NAAT technology, short for nucleic acid amplification tests, the same kind used in clinics. These tests detect the genetic material of bacteria like chlamydia, meaning they can catch infections even when symptoms are silent.
Rapid tests for syphilis and HIV are also available. These use blood from a finger prick and provide results within minutes. Accuracy increases when testing is done at the right time, typically two to three weeks after exposure. If you’re unsure when to test, use the Window Period Calculator.
Micro-Scene: How One Test Gave Alex His Answers
Alex, 29, had been debating a doctor visit for weeks. He didn’t want to explain his symptoms to a receptionist, and he definitely didn’t want to wait in a clinic with strangers. His right testicle felt weird, like it had dropped and shrunk a little. No pain. No visible swelling. Just…different. He ordered a 5-in-1 home kit, peed in a cup, swabbed his throat (he’d had oral sex too), and mailed it off. Three days later, the app pinged: positive for gonorrhea. No guessing. No Googling. Just facts, and a clear next step.
"If your head keeps spinning, peace of mind is one test away." You can start by ordering a 8-Panel STD Test Kit discreetly delivered to your door.
How to Talk to Your Partner About This
Let’s be real, telling someone your testicle is shrinking isn’t exactly bedroom talk. But if you’re in a relationship, transparency matters. Most STDs are shared unknowingly because symptoms are subtle or absent. A lot of damage happens in silence.
You don’t have to start with shame. Try: “I noticed something feels off down there, and I want to be proactive. I ordered a test to rule things out. Would you want to test with me?”
This changes the tone from blame to partnership. If you test positive, you’ll have already opened the door for a respectful conversation. If negative, you’ve just modeled mature sexual health for both of you.
Can Damage Be Reversed? What Treatment Looks Like
Let’s say the test comes back positive for chlamydia or gonorrhea. You’re not alone, and you’re not stuck. The good news? These infections are curable with antibiotics, and early treatment prevents most long-term complications. But what if the damage has already begun?
Epididymitis and early testicular atrophy can frequently be reversed or stabilized if detected early, before significant inflammation or scarring. Anti-inflammatory drugs lessen swelling, while antibiotics like ceftriaxone and doxycycline eliminate the infection. Using scrotal ultrasonography, urologists can assess sperm health, blood flow, and tissue healing.
In more advanced cases, especially with long-term neglect, testicular function may not fully recover. The tissue may remain shrunken or produce less sperm or testosterone. That’s why timing matters, every week you wait increases the odds of lasting damage.
Retesting After Treatment: When, Why, and How
Seldom is a single test the end of the tale. The CDC advises retesting three months following treatment for gonorrhea or chlamydia to verify clearance and look for reinfection. Even if you are cured, testing too soon (within a few days or a week) may find residual bacterial DNA.
Let’s walk through two common retesting arcs:
1. You had mild symptoms and tested at home. You took antibiotics, symptoms faded. Three months later, you retest to make sure nothing snuck back in. Clean slate.
2. You didn’t have symptoms, but your partner tested positive. You tested negative early but symptoms started later. You test again two weeks in, positive. You treat and then plan a 3-month retest. It’s not over-testing; it’s taking responsibility.
Every STD has different retesting needs. Syphilis often requires repeated blood tests at 6 and 12 months. HIV may need confirmatory NAAT testing depending on the window. At-home kits can handle most of these, and shipping is discreet.
Want to make sure you’re truly clear? Order an 8-Panel STD Home Test Kit and get peace of mind.
People are aslo reading: Trichomoniasis and HIV Risk: What Happens When You Leave It Untreated
What If It’s Hormonal? The Testosterone Connection
Let’s zoom out for a minute. Some testicle shrinkage isn’t caused by infection at all, but by low testosterone. This can result from long-term illness, age, substance use (like anabolic steroids), pituitary issues, or genetic conditions like Klinefelter’s syndrome.
Men with low T often notice testicle shrinkage gradually, alongside other signs like low libido, mood changes, increased body fat, or muscle loss. It’s not the same as the sudden size change from infection, but it’s worth testing.
Some at-home labs now offer hormone panels with finger-prick blood drops. Still, for long-term hormonal issues, working with a clinician is recommended. They may order ultrasounds, semen analysis, and LH/FSH tests to understand the full picture.
If an STD test is negative but you still feel something’s wrong down there, don’t stop searching. Atrophy isn’t always infectious, but it’s always worth understanding.
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The Emotional Fallout: What No One Talks About
Let’s be blunt: realizing one of your testicles is smaller or damaged can hit hard. There’s body image, masculinity, fertility fears, sex drive anxiety, all tangled into a knot of silence. And if it’s linked to an STD, shame can double down.
But here’s the thing: this isn’t just your story. Thousands of men each year face this. Some catch it early and bounce back. Some don’t. But either way, your worth isn’t measured by the size of a gland. You are still whole. Still capable. Still in control.
If you need help processing this, talk to someone. A doctor. A therapist. A partner. You don’t have to go through this with your jaw clenched and your search history full of anxiety. And if you're not ready to talk? Start by testing. That simple action gives you clarity, agency, and options.
Take control of your sexual health today, not because you should feel scared, but because you deserve answers.
FAQs
1. Can chlamydia actually shrink your balls?
Yep. It sounds wild, but it’s medically true. If chlamydia crawls up to your epididymis (that coiled tube behind your testicle), it can inflame the whole system. Leave it alone too long, and the constant inflammation can damage tissue and cut off circulation, leading to shrinkage. No pain doesn’t mean no problem.
2. What does it feel like when your testicle starts shrinking?
It’s not like a balloon deflating. Most guys describe it as one testicle feeling lighter, smaller, or softer than the other. Some notice it hanging differently. No heat, no throb, just…off. And when something down there feels “off,” it usually is.
3. Is it permanent?
It depends on how early you catch it. If the infection’s still active and you treat it in time, your testicle might bounce back, or at least stop shrinking. But if scarring or blood flow loss has already kicked in, that change might stick. Either way, getting treated ASAP gives you the best shot at recovery.
4. Can an STD mess up both testicles?
It’s rare, but yeah, it can happen, especially if the infection spreads or goes untreated for a long time. Most cases are one-sided, but if you’re ignoring symptoms or playing guessing games, you’re rolling the dice with both.
5. Is it still possible to get someone pregnant if one testicle shrank?
In many cases, yes. One healthy testicle can handle the job just fine. But if both testicles are affected, or if the damage is severe, your fertility might take a hit. A semen analysis can tell you more than a mirror ever will.
6. What if my STD test came back negative, but one testicle still feels weird?
Then it’s time to think outside the STD box. Testicular torsion, hormonal issues, varicocele, trauma, there are plenty of non-STD reasons for changes in size or feel. If something’s changing down there, get it checked. An ultrasound can see what your eyes can’t.
7. Can I fix this with vitamins, ice, or “natural” stuff?
We get it, you’d love for this to be a zinc deficiency or a bad workout. But infections don’t respond to supplements. If an STD or internal inflammation is in play, you need antibiotics, not essential oils. Don’t DIY your health when one test could clarify everything.
8. How do I know what’s normal down there?
No one teaches this in sex ed. But generally: your testicles should feel firm, not hard. One might hang lower (that’s normal), and some small size difference is okay. What’s not normal? A sudden change in feel, shape, weight, or size, especially if it’s just one side.
9. I’m too embarrassed to go to a clinic. What now?
That’s exactly why at-home testing exists. You pee in a cup or swab what’s needed, drop it in the mail, and get results online. No waiting room. No awkward eye contact. If something feels off, this is your no-excuses path to peace of mind.
10. Is a shrinking ball a reason to panic?
Not panic, but definitely pay attention. It’s your body’s way of saying, “Hey, something’s going on.” You don’t have to spiral. You just have to act. Test. Treat. Then heal, physically and emotionally. You’re not the first guy this has happened to, and you won’t be the last.
You Deserve Answers, Not Assumptions
It’s easy to write this off. To assume it’s nothing. That maybe it’s always been like that. Or that it’ll go away on its own. But your body isn’t asking for assumptions, it’s asking for action. If your testicle feels smaller, heavier, higher, or just weird, you don’t need to panic. But you do need clarity.
Getting tested doesn’t mean you’re dirty. It means you’re tuned in. You care. You’re stepping up. And with at-home STD test kits, that step doesn’t require a clinic or confession. It just takes a few minutes, some privacy, and a willingness to know the truth.
You deserve peace of mind. You deserve a plan. You deserve a body that works, and a future that feels stable. So stop guessing. Start knowing.
Order your test kit now. Not because you're afraid, but because you're done waiting in the dark.
How We Sourced This Article: We combined current guidance from leading medical organizations with peer-reviewed research and lived-experience reporting to make this guide practical, compassionate, and accurate.
Sources
1. Epididymitis: Symptoms & Causes (Mayo Clinic)
2. Epididymitis – An Overview (American Family Physician)
3. Outcome of acute epididymo‑orchitis: Risk factors for testicular loss or atrophy (PMC)
4. Male infertility due to testicular disorders (PMC)
5. Testicular Atrophy: Symptoms, Causes & Treatment (Healthline)
7. Viruses in the mammalian male genital tract and their effects on testicular atrophy (PMC)
About the Author
Dr. F. David, MD is a board-certified infectious disease specialist focused on STI prevention, diagnosis, and treatment. He blends clinical precision with a no-nonsense, sex-positive approach and is committed to expanding access for readers in both urban and off-grid settings.
Reviewed by: J. Evans, PA-C | Last medically reviewed: November 2025
This article is for informational purposes and does not replace medical advice.
