Shrinking testicles can happen with age, low testosterone, infection, varicocele, injury, or an urgent problem that needs care.
Noticing that your testicles seem smaller can throw you off fast. In many cases, there’s a clear medical reason behind it. Sometimes the change is mild and slow. Sometimes it comes with pain, swelling, a lump, trouble with sex drive, or fertility concerns. The pattern matters.
The testicles make sperm and most of the body’s testosterone. When they shrink, doctors often call it testicular atrophy. That term does not name one disease on its own. It means the tissue has lost volume, and the next step is working out why.
Why Are My Testicles Getting Smaller? Common Causes
There are a handful of causes doctors think about first. Some are common and treatable. Some need quick attention.
Low testosterone or hormone imbalance
If the body is not getting the right hormone signals, the testicles may shrink over time. This can happen with aging, pituitary problems, certain long-term illnesses, or after use of outside testosterone or anabolic steroids. Steroid use is a classic cause: the body stops sending the signal that tells the testicles to keep working, so they can get smaller and sperm production can drop.
Varicocele
A varicocele is a group of enlarged veins in the scrotum. It often shows up on the left side. Some men feel a dull ache, a dragging feeling, or notice that one testicle looks smaller than the other. Mayo Clinic’s varicocele page notes that poor growth of a testicle can happen with this condition.
Infection and inflammation
Orchitis is inflammation of a testicle. It may follow a viral illness such as mumps, or come with bacterial infection. You may notice pain, swelling, fever, or tenderness first. Later, the affected side can shrink. That change is more concerning when it follows a painful or swollen episode you brushed off weeks or months ago.
Injury
A direct hit, sports injury, surgery, or damage to blood flow can leave the testicle smaller later on. One injured testicle does not always mean low testosterone for life. The other side can often keep making enough hormone. Even so, size loss after trauma is worth getting checked.
Testicular torsion
This is one of the big red-flag causes. Torsion means the testicle twists and cuts off its own blood supply. It usually causes sudden, severe pain, swelling, nausea, or a testicle that sits higher than usual. Mayo Clinic advises emergency care for sudden or severe testicle pain. If blood flow is cut off too long, the testicle can be damaged and later shrink.
Cancer
Many people think testicular cancer always makes a testicle bigger. That can happen, but any clear change in size, shape, firmness, or feel should be checked. Cancer is not the most common cause of a smaller testicle, yet it must stay on the list. The NHS page on testicular cancer symptoms says swelling, a lump, pain, or a testicle getting bigger can be warning signs.
Clues That Point Toward One Cause Or Another
The details around the size change often tell the story better than the size change alone. Ask yourself what else came with it, when it started, and whether one side or both sides changed.
- Slow change over months: more in line with hormone issues, steroid use, aging, or varicocele.
- Pain first, shrinkage later: raises concern for prior torsion, orchitis, or injury.
- One side only: often points to varicocele, past infection, trauma, torsion, or a local growth.
- Both sides: leans more toward hormone trouble, steroid use, heavy illness burden, or cancer treatment effects.
- Low sex drive, erection trouble, less facial hair, low energy: can fit low testosterone.
- “Bag of worms” feeling above a testicle: classic for varicocele.
- New lump, hardness, or shape change: get examined soon.
Also, some size difference is normal. One testicle often hangs a bit lower or feels a bit different. What matters is a new change from your usual pattern.
What Testicle Shrinkage Can Mean For Fertility And Testosterone
Smaller testicles do not always mean infertility or low testosterone. Still, the chance goes up when the shrinkage is linked to steroid use, varicocele, orchitis, chemotherapy, radiation, or longstanding hormone trouble.
A man can have one smaller testicle and still father children. He can also have normal testosterone with one damaged side. But if you’ve noticed shrinkage along with less sex drive, fewer morning erections, reduced semen volume, or trouble trying to conceive, that changes the picture. A doctor may want blood tests and, in some cases, a semen analysis.
| Possible Cause | Common Clues | What To Do |
|---|---|---|
| Low testosterone | Both sides may seem smaller, lower sex drive, erection trouble, fatigue | Book a clinic visit for an exam and hormone testing |
| Anabolic steroid or outside testosterone use | Shrinkage over time, lower sperm count, body-building drug history | Tell your doctor exactly what you used and when |
| Varicocele | One side, often left; dull ache; “bag of worms” feel | Get examined; ultrasound may be needed |
| Orchitis | Pain, swelling, fever, illness first, smaller size later | Seek medical care; treatment depends on the cause |
| Injury | Blow to the groin, swelling or bruising, later size loss | Get checked, especially if pain or swelling was severe |
| Testicular torsion | Sudden severe pain, swelling, nausea, high-riding testicle | Go to urgent care or the ER right away |
| Cancer | Lump, firmness, shape change, heaviness, ache | Book a prompt exam and ultrasound |
| Age-related change | Slow mild change, no lump, no sudden pain | Still mention it at your next visit if it’s new to you |
When You Should Not Wait
Some symptoms move this from “book an appointment” to “go now.” Sudden scrotal pain is the standout one. Torsion can damage a testicle in hours, not days.
Get urgent care right away if you have:
- sudden or severe pain in a testicle or the scrotum
- rapid swelling
- nausea or vomiting with scrotal pain
- a testicle that sits higher than usual
- fever with marked pain and swelling
- blood in the urine after an injury
If the change is painless but new, don’t sit on it for months either. A lump, growing firmness, or clear change in one testicle still deserves a proper exam.
How Doctors Check Why A Testicle Is Smaller
The visit usually starts with a history and a physical exam. The doctor will ask when you noticed the change, whether it came with pain, whether you use testosterone or steroids, whether you had mumps, an STI, a groin injury, surgery, or fertility trouble.
Next comes the exam. The doctor checks the testicles, the epididymis, and the veins above the testicle. He may ask you to stand, cough, or lie down, since a varicocele can feel different in each position.
Tests You May Need
Not every man needs every test. These are the ones used most often:
| Test | What It Shows | When It Helps |
|---|---|---|
| Scrotal ultrasound | Size, blood flow, varicocele, cyst, mass, signs of damage | Best first test for most new size changes |
| Blood hormone panel | Testosterone, LH, FSH, and related hormone clues | Useful with low sex drive, erection trouble, or both sides shrinking |
| Urine or STI testing | Signs of infection | Used when pain, burning, fever, or discharge is present |
| Semen analysis | Sperm count and quality | Used when fertility is a concern |
Can A Smaller Testicle Go Back To Normal?
Sometimes no. Once tissue is damaged, the size change may stay. That said, the body can still function well with one smaller testicle, depending on the cause and how much healthy tissue remains.
What can improve is the reason behind the change. Treating infection, fixing a large varicocele in selected cases, stopping anabolic steroids, or treating hormone trouble may help function, symptoms, or fertility. The earlier the cause is found, the better your odds of avoiding more loss.
What To Do Next If You’ve Noticed A Change
If you’re asking, “Why are my testicles getting smaller?” don’t try to diagnose it from photos or forum posts. Check what has changed and how fast it happened. Think about pain, swelling, lumps, sex drive, injuries, steroid use, and whether one side or both sides changed.
Then act on the pattern:
- If the pain is sudden or severe, get urgent care.
- If there’s a lump, new firmness, or a steady one-sided change, book a prompt exam.
- If both sides seem smaller and you also have hormone symptoms, ask for hormone testing.
- If you use testosterone, anabolic steroids, or fertility drugs, tell the doctor plainly.
This is one of those body changes that is worth checking, even when it turns out to be something manageable. A good exam and, if needed, an ultrasound can sort out a lot fast.
References & Sources
- Mayo Clinic.“Varicocele – Symptoms and causes.”Explains that a varicocele may cause poor development of a testicle and fertility trouble.
- Mayo Clinic.“Testicular torsion – Symptoms & causes.”States that sudden or severe testicle pain needs emergency care since torsion can damage or destroy the testicle.
- NHS.“Symptoms of testicular cancer.”Lists lump, swelling, pain, and a testicle getting bigger as warning signs that need medical assessment.