TESTOSTERONE LEVELS & TESTING: THE COMPLETE GUIDE

A common belief about testosterone is that it boils down to your sex drive. A higher sex drive can indicate more testosterone but you’ll soon find out that it does much more than that. It helps you with other factors like building muscle mass, increasing bone strength, improving your energy and your overall mood. Your levels will also naturally change as you get older.

One number on its own on a blood test doesn't tell you much. A "normal" result can still come back with symptoms. On that same note, a result outside the range doesn't always mean something is wrong. What matters is the full picture of your age, symptoms, as well as the blood result.

This full guide walks you through it all:

• What testosterone does

• What counts as a normal level, and why that's not as simple as it sounds

• How to spot the signs of levels that are too low or too high

• What actually works for raising testosterone naturally

• How testing and treatment work, including where TRT fits in

No scare tactics here, just clear answers that will help you understand how testosterone testing works. If you want to know exactly where you stand, a simple blood test is the only way to know for sure, coupled with expert advice from a doctor.

Testosterone helps with a multitude of things that play a key role in how men function and feel.

It helps with the following:

• Builds and maintains lean muscle mass

• Supports bone density

• Produces red blood cells

• Affects how you feel

That's why low testosterone can show up in ways that don't seem obviously hormone-related. You may have symptoms, but these aren't always testosterone-related. Having said that, testosterone is often part of the picture.

Testosterone levels are highest in your late teens and twenties. After your twenties your levels will slowly decline from around 30. This is completely natural and happens slowly over time. A "healthy" level for you can shift over time. This is why understanding your own levels is more insightful than comparing it to a generic average.

On average, levels drop by around 1% a year once you enter your 30’s. As you can imagine, this adds up over a couple of decades.

This is one reason "normal" is a moving target. A level that would be considered low for a 25 year old might be completely common for someone in their 50s and beyond.

Blood testing labs also don't agree on a single normal range. Every lab has its own reference range that they adjust according to the population they serve. In general, the range is from about 6 to 25 nmol/L but this can vary quite a bit between labs.. 

It's also worth knowing that reference ranges across the UK population have been drifting downward over time. Rising rates of obesity and type 2 diabetes are thought to be two of the key drivers of this change.

This is why doctors tend to think less in terms of "normal" and more in terms of action points:

These aren't hard cutoffs, and they're not a substitute for a proper conversation with a doctor. But they're a far more useful way to think about your result than simply asking whether it falls "within range."

Testosterone testing isn't only relevant to adult men. Levels may also be tested in boys if it looks like they are starting puberty earlier than expected, generally before the age of 9. 

If you had a test recently and staring at your results you’re probably trying to make sense of it. It's tempting to want a simple yes or no when it comes to your score. Is it low? Is it high? Is it fine?

The honest answer is that a number by itself doesn't tell the full story, as mentioned previously. A few things need to line up before that result means much at all.

Timing - Testosterone naturally peaks in the morning, so the most reliable results come from a fasting test done between 7 and 11 am. Testing later in the day can give a lower reading that doesn't reflect your true levels.

Age - A number that's low for a 25 year old could be entirely typical for a 55 year old, which is why the action points in the table above are a better guide than a single "normal" range.

A single number isn't always enough - If your result sits in a grey area, checking free testosterone and a marker called SHBG can help build a clearer picture, since these show how much testosterone your body has available to use.

So a proper testosterone result isn't just one number. It's a combination of the figure itself, when and how it was tested, your age, and your symptoms. Put all of that together and you get a far clearer answer than the number could ever give you alone.

Symptoms

Low testosterone can show up in a few ways which you may notice. The symptoms we typically see are:

• Tiredness / fatigue

• Low mood

• Low libido / depression

• Erectile Dysfunction

• Muscle loss

• Loss of body hair

You may look at these symptoms and experience a couple or none at all. However here’s what you need to know. These symptoms can overlap with a lot of other conditions. That’s why you shouldn't diagnose yourself. 

Only a blood test can give you an official diagnosis, not symptoms alone. You may have heard of a "low testosterone face." There's no reliable evidence to support this as something you can diagnose from appearance.

What Causes It

So what causes low testosterone? There are many possibilities. However the most common are type 2 diabetes and obesity.

Along side these common causes, lifestyle factors play a major part as well. This includes legal and illegal drugs such as:

• Opiate medication

• Marijuana (including medical)

• Excess alcohol

• Poor quality sleep

• Certain mental health medications

Less commonly, low testosterone can be caused by problems with the testicles. For example, these include things like previous injury or infection or problems with the pituitary gland.

Symptoms

So with low testosterone symptoms out the way, what about when it’s too high? Most men won't notice any symptoms unless levels are very high, and when they are, it's almost always because someone is taking testosterone as a medication or injecting it, rather than a naturally occurring issue. Genuine medical causes of high testosterone exist, but they're rare.

When levels are high enough to cause symptoms, these can include anger and irritability, excess hair growth, acne, water retention, breast tissue growth, and shrinking testicles.

The Real Risk: Sustained High Levels

The more serious risk is what happens with sustained high levels, and this is where steroid misuse becomes seriously dangerous. Testosterone plays a role in producing red blood cells. 

So taking too much can raise your blood count which leads to consequences. These include making the blood thicker which leads to clotting issues. Blood clotting can lead to heart attacks and strokes regardless of age. So even if you’re young and fit, this is still a risk factor.

There's a second risk that's less talked about. Taking high doses of testosterone over a long period can switch off your body's natural production entirely. If this happens for long enough, at high enough doses, the shutdown can become permanent, meaning your body never fully recovers its own production, and you're left needing medication indefinitely.

Why Unregulated Sources Are Dangerous

Testosterone bought outside of a proper medical setting isn't tested, isn't monitored, and there's no way to know what you're putting into your body. On a legitimate TRT programme, levels and blood count are checked regularly to keep things safe. Without that oversight, you're taking a real risk with your health.

Good news first. The evidence that lifestyle changes can boost testosterone is strong. This isn't wishful thinking; it's one of the more well-supported areas of testosterone research.

Keeping your weight within a healthy range, roughly a BMI of 19 to 25, is one of the most practical things you can do to support healthy testosterone levels, given how strongly obesity is linked to low levels.

What really works:

• Maintaining healthy weight

• Exercise (mostly HIIT and weight training)

• Stress management

• Good quality sleep

• Avoiding recreational drugs (especially excess alcohol and opiates)

Notice what's not on that list. There's no single "miracle food" that boosts testosterone, no matter how often you see one claimed online. The real lever is your overall diet. Eating well enough to avoid becoming overweight or developing type 2 diabetes does far more for your testosterone than any one ingredient ever could.

Now for two myths worth clearing up. Masturbation does not reduce testosterone. Abstaining, including the popular idea of a 7 day break, doesn't meaningfully raise it either. There may be a brief spike right after abstaining, but it doesn't translate into any real, lasting benefit. If you've seen either claim online, you can safely ignore it.

If any of the symptoms covered earlier sound familiar, or you're simply curious where you stand, testing is the only way to know for sure.

GP or Private Testing

You can ask your GP for a testosterone test, but they'll usually only run one if it's clinically justified, since they have a responsibility to manage NHS resources carefully. In practice, erectile dysfunction is the symptom most likely to get you a test through your GP. If your situation doesn't quite meet that bar, or you'd simply rather not wait, testing privately is a straightforward alternative.

Timing and Fasting

However you get tested, timing matters. Testosterone is highest in the morning and gradually falls through the day, so the most accurate results come from a fasting test taken between 7 am and 11 am. Testing too late in the day can make your levels look lower than they truly are.

Total vs. Free Testosterone

You might also come across different types of testosterone tests and wonder which one you need. Total testosterone is the standard test, and it's the most useful for both diagnosis and monitoring. In your blood, testosterone exists either bound to proteins such as SHBG and albumin or unbound, known as free testosterone. 

Free testosterone doesn't usually add much extra information, but in cases where SHBG is unusually high or low, checking free testosterone helps confirm whether low testosterone is behind your symptoms.

Home Testing vs. Clinic

If you're testing at home rather than in a clinic, it's worth knowing that a finger-prick sample is processed in exactly the same way as a sample taken from a vein. As long as it's collected correctly, the accuracy is the same, so you don't need to choose a clinic visit purely for accuracy's sake.

Choosing the Right Test

To make choosing simple, here's how our testosterone tests break down:

When Is Treatment Confirmed

If your testosterone comes back low, treatment isn't automatic. It's confirmed when you have both typical symptoms and a total testosterone level below 12. If you don't have symptoms, treatment usually isn't necessary, even if your number is on the lower side.

How TRT Is Given

Where treatment is needed, testosterone replacement therapy, or TRT, is given either as a gel or as an injection. Injections can be given at different intervals depending on the type used. All of these methods work effectively, so the choice mostly comes down to personal preference.

TRT as a Short-Term Motivator

There's an interesting shift happening in how TRT is used. Low testosterone often saps motivation, which makes it genuinely difficult to start the lifestyle changes that would improve it naturally. 

Newer guidelines recognise this, and now support using TRT short-term in some cases, specifically to help someone regain enough energy and motivation to lose weight or make other changes. Once those changes take hold, treatment can sometimes be stopped, with natural testosterone production picking back up on its own.

Why the NHS Has Been Cautious

You may have heard that testosterone treatment is hard to get on the NHS, and historically that's been true. A few things explain why. Low testosterone has often been under-recognised as a condition, and the benefits of treating it, like protecting bone density and supporting healthy blood count, haven't always been widely understood. 

There's also been longstanding concern about side effects, particularly around prostate cancer and heart disease risk. Current evidence tells a more reassuring story. Research suggests TRT doesn't increase the risk of prostate cancer, and it may even be beneficial for cardiovascular health.

Worth being clear on one thing. TRT is a prescription treatment, and getting started on it means going through a GP or a suitably qualified doctor. Testing your levels first is the sensible starting point, since it gives you and any doctor you speak to a clear, accurate picture to work from.

Reading about testosterone only gets you so far. If any of this sounds familiar, whether it's the symptoms, the questions about your levels, or just wanting to understand your own health better, testing is the next step.

Our testosterone tests are designed to fit however you want to test. Choose a single, straightforward total testosterone test if you're testing for the first time, or a more detailed panel if you want the fuller picture from the start.

Once you have your results, you don't have to make sense of them alone. You can book a GP consultation to talk through what your numbers actually mean, with a real doctor who can explain your results properly and help you decide on next steps, whether that's lifestyle changes, further testing, or a referral for treatment.

This guide draws on published research and clinical guidelines, including:

• Hwang K, Miner M. Controversies in testosterone replacement therapy: testosterone and cardiovascular disease. Asian J Androl. 2015 Mar-Apr;17(2):187-91. doi: 10.4103/1008-682X.146968. PMID: 25652628; PMCID: PMC4650472.

• Bhasin S, Travison TG, Pencina KM, O'Leary M, Cunningham GR, Lincoff AM, Nissen SE, Lucia MS, Preston MA, Khera M, Khan N, Snabes MC, Li X, Tangen CM, Buhr KA, Thompson IM Jr. Prostate Safety Events During Testosterone Replacement Therapy in Men With Hypogonadism: A Randomized Clinical Trial. JAMA Netw Open. 2023 Dec 1;6(12):e2348692. doi: 10.1001/jamanetworkopen.2023.48692. PMID: 38150256; PMCID: PMC10753401.

• Handelsman DJ, Yeap B, Flicker L, Martin S, Wittert GA, Ly LP. Age-specific population centiles for androgen status in men. European Journal of Endocrinology. 2015;173(6):809-817.

• Roche Diagnostics. Elecsys Testosterone II. Cobas. 2025.

• Travison T, Araujo A, O'Donnell A, Kupelian V, McKinlay J. A Population-Level Decline in Serum Testosterone Levels in American Men. The Journal of Clinical Endocrinology & Metabolism. 2007;92(1):196-202.

• NHS. Male menopause (late-onset hypogonadism). nhs.uk/conditions/male-menopause/

• Hackett G, Kirby M, Rees RW, Jones TH, Muneer A, Livingston M, Ossei-Gerning N, David J, Foster J, Kalra PA, Ramachandran S. The British Society for Sexual Medicine Guidelines on Male Adult Testosterone Deficiency, with Statements for Practice. World J Mens Health. 2023 Jul;41(3):508-537.

• Bhasin S, Brito JP, Cunningham GR, Hayes FJ, Hodis HN, Matsumoto AM, Snyder PJ, Swerdloff RS, Wu FC, Yialamas MA. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. The Journal of Clinical Endocrinology & Metabolism. 2018 May;103(5):1715-1744.