Risks of testosterone treatment

Read this before your consultation, not after. Your doctor will go through it with you and you can ask about anything in here. We'd rather you came to that call having already thought about it.

Testosterone replacement is a well-established treatment. What follows is everything that comes with it, including the parts that are easy to leave out of a sales page.

---

This is a long-term commitment, not a trial run

Most men who start testosterone stay on it. Not because it's addictive in the ordinary sense, but because of how it works. Once you're taking testosterone, your body stops making its own. Come off, and you're not back where you started — you're below it, for months, while your own production restarts. If it restarts fully.

So the decision in front of you isn't really "should I try this for a while." It's closer to "am I prepared to do this for the foreseeable future."

Fertility — read this part twice

Testosterone shuts down sperm production. Not occasionally, and not in a minority of men. It's reliable enough that it has been trialled as a male contraceptive, and it worked.

Most men on standard doses stop producing sperm altogether within three to six months. In the contraceptive research the median was around four months.

For most men this reverses after stopping, but it takes time — commonly six to twelve months, sometimes longer. Two things make recovery slower and less certain: your age, and how long you were on treatment. A 35-year-old who was on it for a year has a considerably better outlook than a 50-year-old who's been on it for six.

And in some men it doesn't fully come back. There is no test we can run beforehand that tells you which group you're in.

If there is any chance you'll want children — not a firm plan, a chance — say so before you start. Storing sperm is straightforward and not expensive, and it's the one thing that makes this decision reversible. There are also treatment approaches that protect fertility better than others. Both of those conversations need to happen before your first injection, not after.

Your blood gets thicker

Testosterone tells your body to make more red blood cells. Within limits that's harmless. Past a point your blood thickens enough to raise the risk of a clot.

This is the single most common reason a man's dose gets changed, and it's the main thing we monitor for. It happens more with injections than with gels, more in older men, and more in smokers.

We measure it before you start, again a few months in, and then at every review. If it climbs too high, the usual answer is lowering your dose or changing how often you inject. Occasionally it means having blood taken off, and sometimes it means stopping.

If you've ever been told your blood was too thick, or had blood removed for that reason, tell your doctor before you start.

Your heart and circulation

This has been argued over for a decade, and there's now a reasonable answer.

A large trial published in 2023 followed more than 5,000 men with low testosterone who either had heart disease or were at high risk of it. Over several years, the men on testosterone had no more heart attacks, strokes or cardiac deaths than the men on placebo. That's the best evidence available and it's genuinely reassuring.

The same trial found three things happened more often on testosterone: an irregular heart rhythm called atrial fibrillation (3.5% compared with 2.4%), a clot on the lung (0.9% compared with 0.5%), and a sudden drop in kidney function (2.3% compared with 1.5%). Small differences in absolute terms. Not nothing.

If you've had a blood clot before, or a heart attack or stroke in the past six months, treatment may not be appropriate, or may need to wait. Your doctor will work through this with you.

Your prostate

Current evidence does not show that testosterone causes prostate cancer. That question has been studied hard and the answer is reasonably settled.

What it can do is raise your PSA, the blood marker used to screen for prostate problems, and — if you already had an undetected prostate cancer — potentially speed it up. That's why we check your PSA before you start and keep an eye on it afterwards.

It can also worsen urinary symptoms if your prostate is already enlarged. Getting up at night to urinate, a weak stream, trouble starting. Mention these if you have them.

Sleep apnoea

If you have sleep apnoea and it isn't being treated, testosterone can make it worse. If you snore heavily, wake up unrefreshed, or your partner has told you that you stop breathing at night, raise it at your consultation. Untreated apnoea is worth sorting out in its own right, and it's also one of the things that can cause low testosterone in the first place.

The everyday stuff

Common, mostly manageable, worth knowing about:

Acne and oily skin. Usual in the first few months and normally settles.

Breast tissue. Some testosterone converts to oestrogen, and in some men that means tender or enlarged breast tissue. It's dose-related and there are ways to manage it.

Your testicles will shrink. They're no longer being asked to do anything. This is expected rather than a complication, and it partly reverses if you stop.

Mood. Most men report feeling steadier. A minority feel more irritable or short-fused, usually early on or when the dose is too high. If your mood gets worse, that's a reason to contact us, not to push through it.

Injection sites. Soreness and the odd bruise. Infection is rare, but a site that becomes hot, red, spreading or comes with a fever needs attention that day.

Fluid retention. Some men hold water in the early weeks. It matters more if you have heart or kidney problems.

Sleep. A few men find their sleep gets worse, particularly at higher doses.

Stopping

You can stop whenever you want. Nobody will try to talk you out of it.

But be clear about what stopping involves. Your own production has been switched off and it takes months to come back — sometimes longer, occasionally not completely. During that stretch you'll probably feel worse than you did before you ever started: flat, tired, low libido, low mood.

That's not an argument for staying on treatment you don't want. It's an argument for planning the exit with your doctor rather than just quitting. And if you're stopping because something's gone wrong, tell us first. Most problems on testosterone are dose problems.

What isn't settled

Testosterone has been prescribed for decades and the short and medium-term picture is well studied. What's thinner is the long view. There's limited high-quality data on men who stay on treatment for fifteen or twenty years, because those trials haven't been done.

That isn't a reason to avoid treatment. It is a reason to stay monitored, and a reason for us to be straight with you about where the evidence actually sits rather than implying it's complete.

How the risks are actually managed

Monitoring. That's the whole answer, and it only works if you turn up for it.

Before you start — bloods, including testosterone, a full blood count, PSA where appropriate, and the rest of your panel.

Around three months in — bloods again. This is where a rising red cell count gets caught early, while adjusting the dose is still a small thing.

Then at every review — ongoing bloods and a proper look at how you're going.

If you don't complete your bloods, we can't keep prescribing. That isn't an administrative preference. Prescribing testosterone without monitoring is unsafe, and we won't do it.

When to get help urgently

Go to an emergency department, or call 000, for:

• Chest pain, or shortness of breath that comes on suddenly
• Swelling, pain or redness in one leg
• Weakness down one side, trouble speaking, or a sudden severe headache
• An injection site that's hot, red and spreading, especially with a fever

For anything else — mood changes, worse sleep, breast tenderness, or just something that doesn't feel right — message us through the portal. Most of it is fixable with a dose adjustment.

What you're agreeing to

By ticking the box, you're confirming that:

• You've read this and understood it
• You've had the opportunity to ask questions, and you'll have another at your consultation
• You understand that testosterone will very likely make you infertile while you're taking it, and that this is occasionally permanent
• You understand this is ongoing treatment that requires ongoing monitoring, and that treatment stops if monitoring stops
• You understand your doctor may decide testosterone isn't appropriate for you, and that your consultation fee covers the assessment either way
• The health information you've given us is accurate and complete as far as you know

This is not a waiver. It doesn't remove your rights, and it doesn't reduce your doctor's responsibility for your care. It records that you were told.

Your doctor will go through all of this with you at your consultation. If anything here worries you, that conversation is exactly what it's for.