Low testosterone in men is easy to suspect and surprisingly hard to confirm. Testosterone follows a daily rhythm, so the same man can produce a normal figure at 8 a.m. and a low one at 4 p.m. A single reading, especially an afternoon one, therefore settles very little. Guidelines ask for two low morning samples taken on different days before anyone uses the word hypogonadism.
In this article you’ll learn how the testosterone test actually works, why timing and repeat sampling matter so much, what total and free testosterone mean and why SHBG shifts them, how doctors separate a testicular problem from a pituitary one, which symptoms genuinely point to the diagnosis, which reversible causes are worth finding first, and what treatment involves, including its effect on fertility.
What testosterone does, and what the blood test measures
Testosterone is the main androgen in men. Most of it is made by the Leydig cells of the testes, under instructions from two pituitary hormones: luteiniserande hormon (LH) och follikelstimulerande hormon (FSH). LH drives testosterone production; FSH supports sperm production alongside it. This chain, running from the hypothalamus to the pituitary to the testes, is called the hypothalamic-pituitary-gonadal axis, and a fault anywhere along it can lower the final number.
Testosterone supports muscle and bone, red blood cell production, sexual desire, erectile function and the development of male characteristics at puberty. Women make it too, at far lower levels, which is why högt testosteron hos kvinnor is a separate clinical question. A standard blodprov för testosteron measures total testosterone: everything in circulation, bound and unbound together. That figure is where every assessment starts, but on its own it answers fewer questions than most people expect.
Why timing and repeat testing matter more than the number
Testosterone has a strong diurnal rhythm. Levels peak in the early morning and drift down across the day, and in younger men the fall can be large enough to move the same person from a normal to a low result inside 24 hours. Eating matters too: a meal, and particularly a sugary one, lowers circulating testosterone for a few hours. For both reasons, the sample should be drawn in the morning, generally before 10 a.m., and after an overnight fast.
The second rule is the one most often skipped. A low result is not a diagnosis. The Endocrine Society and the American Urological Association both advise confirming an initial low reading with a second morning sample on a separate day before hypogonadism is diagnosed. The 2025 European Association of Urology update takes the same position. The large TRAVERSE safety trial applied that standard to recruitment: men had to have two low fasting testosterone measurements to enter.
There is a practical reason for repeating. Testosterone varies from day to day in the same man, laboratory assays differ, and a passing illness, a stretch of poor sleep or a stressful week can push a single result down. A second morning test filters out a large share of false positives. It also explains why a result from a walk-in or mail-order panel drawn at lunchtime should never be treated as a verdict.
Total testosterone, free testosterone and why SHBG matters
Most testosterone in blood is not free to act. A large share is bound tightly to sex hormone-binding globulin (SHBG) and much of the rest is bound loosely to albumin. Only a small fraction circulates unbound. Free testosterone is that unbound fraction, and it is the part most closely related to what body tissues actually experience.
SHBG explains a great many confusing results. Anything that raises SHBG, including aging, an overactive thyroid, liver disease and estrogen, pushes total testosterone up without necessarily raising the free fraction. Anything that lowers SHBG, including obesity, insulin resistance and type 2 diabetes, an underactive thyroid, glucocorticoids and nephrotic syndrome, pulls total testosterone down while the free fraction may sit close to normal.
That is why free testosterone is treated as a second-line test, used when total testosterone falls near the diagnostic threshold or when SHBG is likely to be shifted. It is a tiebreaker rather than a routine first measurement. In most laboratories it is calculated from total testosterone, SHBG and albumin rather than measured directly, and those calculators are not standardized between centers, so a borderline free testosterone deserves interpretation rather than acceptance at face value.
Symptoms: which ones point to low testosterone, and which do not
Symptoms fall into two very different groups, and blurring them is the commonest reason men are tested unnecessarily.
The more specific features are reduced or absent morning erections, a clear fall in sexual desire, loss of body and facial hair, small or shrinking testes, breast tissue development (gynecomastia), hot flashes and infertility. When the problem begins before puberty, incomplete sexual development is added to that list. These findings genuinely raise the probability of hypogonadism and are the ones a doctor will ask about most closely.
The non-specific features are the ones men actually notice: fatigue, low mood, poor concentration, reduced strength, weight gain and broken sleep. Every one of them overlaps heavily with obstruktiv sömnapné, depression, thyroid disease, anemia, poorly controlled diabetes, medication side effects and simply not sleeping enough. Because of that overlap, the Endocrine Society advises against measuring testosterone in men who have only non-specific symptoms, since most low results found that way turn out to reflect something else.
Erectile dysfunction sits awkwardly between the two groups. Low testosterone can reduce desire and contribute to erection problems, but blood vessel disease, diabetes, medication and psychological factors cause far more cases, so a testosterone result rarely explains it alone.
Primary or secondary hypogonadism, and the tests that sort them
Once two low morning readings are confirmed, the next question is where the fault sits. LH and FSH answer it, which is why they are measured alongside testosterone rather than afterwards.
In primary hypogonadism the testes are the problem. Testosterone is low while LH and FSH are high, because the pituitary is signaling hard to a gland that cannot respond. Causes include Klinefelter syndrome, mumps orchitis, testicular injury or torsion, undescended testes, chemotherapy and radiation.
In secondary hypogonadism, sometimes called central hypogonadism, the signal is the problem. Testosterone is low but LH and FSH are low or inappropriately normal, meaning normal-looking values that should have risen in response. Causes include pituitary tumors, raised prolactin, opioids, glucocorticoids, iron overload, severe obesity, anabolic steroid use and serious illness.
When the pattern looks central, further tests usually follow: prolaktin, iron studies including transferrinmättnad to look for hemochromatosis, the other pituitary hormones, and a pituitary MRI where prolactin is high, testosterone is very low, or there are headaches or visual changes. A semen analysis is added when fertility is the concern.
| Resultatmönster | Vad det pekar mot | Vanligt nästa steg |
|---|---|---|
| One low reading taken in the afternoon | Very little on its own; the daily rhythm alone can explain it | Repeat as a fasting morning sample before 10 a.m. |
| Two low morning readings with high LH and FSH | A testicular cause, known as primary hypogonadism | Clinical examination, and genetic testing or semen analysis where indicated |
| Two low morning readings with low or inappropriately normal LH and FSH | A pituitary or hypothalamic cause, known as secondary hypogonadism | Prolactin, iron studies, other pituitary hormones, and pituitary MRI where indicated |
| Low total testosterone but normal free testosterone | Often a low-SHBG state such as obesity or insulin resistance rather than true deficiency | Review SHBG, weight, glucose control and current medicines with a clinician |
Reversible causes worth finding before treatment
A meaningful share of low readings have a cause that can be addressed, and finding it changes what happens next. Excess weight is the largest single contributor in most clinics: fat tissue converts testosterone to estrogen and lowers SHBG, and weight loss often raises testosterone without any hormone treatment at all. Untreated obstructive sleep apnea, heavy alcohol use and any acute illness in the preceding weeks all suppress the axis too.
Medicines are the next group. Long-term opioids and glucocorticoids are well-recognized causes of central suppression. So is anabolic steroid use, whether current or years in the past, and this is worth declaring honestly because it changes the interpretation completely. Raised prolactin, from a pituitary adenoma or from certain drugs, is another cause that is treatable in its own right, and iron overload can damage both the pituitary and the testes.
None of this is a reason to stop or alter a prescribed medicine on your own. Opioids, glucocorticoids and other treatments are prescribed for reasons that matter, and only the prescriber can weigh the trade-off. The useful step is to tell your doctor everything you take, including anything bought without a prescription, so the result is read in context.
What treatment involves, and the fertility question
Testosterone replacement therapy is a prescription treatment for men with a confirmed diagnosis of hypogonadism. It is decided on by a clinician after the diagnosis has been established on repeat morning samples and reversible causes have been considered. It is not an energy, anti-aging or performance treatment. The US Food and Drug Administration states that testosterone products are approved only for men with low testosterone levels alongside an associated medical condition, such as a disorder of the testes, hypothalamus or pituitary.
The most important point to understand before starting is fertility. Testosterone given from outside the body suppresses LH and FSH, which collapses testosterone concentrations inside the testes and impairs sperm production; some men stop producing sperm altogether. Production usually resumes after treatment stops, but the pace varies widely between individuals and recovery is not guaranteed. Any man who might want children, now or later, should raise this before a first prescription rather than after, so that fertility-sparing options can be discussed.
Treatment also means ongoing monitoring rather than a single prescription. Because testosterone stimulates red blood cell production, hematokrit is checked for polycythemia, an over-concentrated blood count. Prostate assessment, including PSA where appropriate, symptoms, blood pressure and sleep apnea are followed as well. The cardiovascular safety question has been studied directly and is covered in the section below.
Because both testing and treatment depend on confirming the diagnosis properly and following it over time, this work belongs with a clinician who can order the right repeat tests, read LH, FSH and SHBG alongside the result, and monitor treatment if it is started.
When to see a doctor about low testosterone
Book an appointment if you have specific features such as a clear loss of sexual desire, absent morning erections, shrinking testes, breast tenderness or enlargement, loss of body hair, or difficulty conceiving. Bring any previous results with you, including the time of day they were taken, and a list of your medicines.
Seek prompt medical advice rather than waiting for a routine appointment if you have: sudden or severe testicular pain or swelling; a breast lump; new headaches together with blurred or narrowed vision; loss of body hair with marked weakness or dizziness; or milky discharge from the nipple. These can point to problems that need assessment quickly, including a pituitary tumor or a testicular condition.
Latest scientific advances in testosterone testing and treatment
The TRAVERSE trial, published in the New England Journal of Medicine in 2023, randomized more than five thousand middle-aged and older men who had symptoms of hypogonadism, two low fasting testosterone readings, and either existing heart disease or a high risk of it. Testosterone gel was no worse than placebo for the combined outcome of cardiovascular death, non-fatal heart attack and non-fatal stroke. The testosterone group did have more atrial fibrillation, acute kidney injury and pulmonary embolism. What this means for you: the main cardiovascular question has been answered reasonably reassuringly, but not perfectly, and the trial studied men with a properly confirmed diagnosis rather than men taking testosterone for tiredness.
A 2026 review in Kardiologia Polska pulled together the randomized and real-world evidence on those non-cardiac signals, alongside the regulatory response. It reports that the boxed warning about major cardiovascular events was removed from testosterone labels, while a class-wide warning about blood pressure increases was added on the basis of ambulatory monitoring studies. What this means for you: safety attention has shifted from heart attacks and strokes to rhythm, kidney, clotting and blood pressure effects, all of which are monitorable. Reliability note: this is a narrative review rather than a pooled analysis, and several of the signals come from observational data, where other differences between patients can distort the picture.
A 2025 review in Nature Reviews Urology examined testosterone replacement and sperm production in men of reproductive age. Androgens taken from outside the body suppress the gonadotropins LH and FSH, sharply reduce testosterone inside the testis, and impair spermatogenesis, the process that makes sperm. Recovery after stopping is usual but follows highly variable timelines that can complicate family planning, and the authors describe exogenous testosterone as contraindicated in men trying to conceive. What this means for you: this is the single most under-communicated harm of testosterone treatment, and it should be discussed before the first prescription.
A 2024 review in Current Opinion in Endocrinology, Diabetes and Obesity looked at calculated free testosterone, the figure most laboratories derive rather than measure. It confirms that aging and obesity move both total testosterone and SHBG, that a low free testosterone can occur alongside a normal total testosterone, and that free testosterone works best as a second-line check that helps avoid both misdiagnosis and overtreatment. What this means for you: if your total and free results seem to disagree, that is a recognized pattern rather than a laboratory error. Reliability note: the authors stress that free testosterone calculators are not standardized, so values are approximations.
A 2025 debate in the Journal of Clinical Endocrinology and Metabolism set out how genuinely unsettled this is. One specialist argued that accurate assessment of free testosterone is useful and supported by evidence; the other argued that the underlying hypothesis is flawed and that free testosterone cannot be measured reliably in ordinary practice. What this means for you: treat a borderline free testosterone as one piece of information to discuss, not a verdict, and expect a good clinician to weigh it against your symptoms, your SHBG and your repeat morning results.
Vanliga frågor
Does low testosterone cause fatigue?
It can, but fatigue on its own is weak evidence. Tiredness is one of the least specific symptoms in medicine and overlaps with sleep apnea, depression, thyroid disease, anemia, poorly controlled blood sugar, medication effects and short sleep. Most men who are tested for tiredness alone and turn out to have a low reading have a different explanation for how they feel. That is why the Endocrine Society advises against measuring testosterone in men whose only complaints are non-specific. If fatigue is your main problem, a broader assessment is usually more productive than a hormone panel.
Will testosterone therapy affect my fertility?
Yes, and this is the most important thing to raise before starting. Testosterone taken from outside the body switches off the pituitary signals LH and FSH, which drops testosterone concentrations inside the testes and impairs sperm production. Some men stop producing measurable sperm. Sperm production usually returns after treatment stops, but the timeline varies a great deal between individuals and full recovery is not guaranteed, particularly after long use. Reviews describe exogenous testosterone as contraindicated for men trying to conceive. If you may want children at any point, say so before the first prescription so alternatives can be discussed.
Do testosterone boosters work?
Over-the-counter testosterone boosters are supplements, not medicines, and they are not held to the standards required of prescription drugs. Evidence that they meaningfully raise testosterone in men with a confirmed deficiency is weak, ingredients and doses vary between products, and some have been found to contain undeclared hormones. They also do nothing about the causes that actually matter, such as excess weight, sleep apnea, alcohol or a pituitary problem. If your testosterone is genuinely low, the useful step is a proper diagnostic work-up with a clinician rather than a supplement.
Can low testosterone cause depression?
Low mood is common in men with confirmed hypogonadism, but the relationship runs both ways and is easy to misread. Depression itself can suppress the hormonal axis, and both conditions share drivers such as poor sleep, chronic illness, alcohol and obesity. A low testosterone result in a man with depressive symptoms does not establish that the hormone is the cause. Depression should be assessed and treated on its own terms, and testosterone results interpreted alongside it rather than instead of it. Tell your doctor about both so neither is missed.
Are the symptoms different in younger men?
The specific symptoms are the same, but the context differs. In a man in his twenties or thirties, a genuinely low testosterone level is less likely to be age-related and more likely to have a findable cause, so it warrants a full work-up rather than reassurance. Anabolic steroid use, past or present, is a frequent explanation, along with obesity, opioids, raised prolactin and pituitary problems. Fertility is also more often an immediate concern, which affects what treatment options are appropriate. The same rule applies: two low morning samples before any diagnosis.
Does low testosterone cause erectile dysfunction?
Low testosterone mostly affects sexual desire rather than the mechanics of an erection. It can contribute to erectile problems, and reduced morning erections are one of the more specific signs, but blood vessel disease, diabetes, high blood pressure, medicines, smoking and psychological factors account for a much larger share of cases. Erectile dysfunction can also be an early marker of cardiovascular disease, so it deserves a proper assessment rather than a hormone test alone. Correcting a confirmed testosterone deficiency does not reliably resolve erectile dysfunction on its own.
Ordlista med nyckeltermer
| Kalla | Definition |
|---|---|
| Testosteron | The main male sex hormone, made mostly in the testes, supporting muscle, bone, red blood cells, sexual desire and male development. |
| Hypogonadism | A clinical diagnosis combining symptoms with persistently low testosterone confirmed on repeat morning samples. |
| Totalt testosteron | All the testosterone circulating in blood, both protein-bound and unbound. The usual first-line measurement. |
| Fritt testosteron | The small unbound fraction, used as a second-line check when total testosterone is borderline or SHBG is likely to be shifted. |
| SHBG | Sex hormone-binding globulin, the protein that carries most testosterone in blood and shifts the total up or down. |
| LH och FSH | Pituitary hormones that instruct the testes. Their pattern separates a testicular cause from a pituitary one. |
| Primär hypogonadism | Low testosterone arising in the testes themselves, with LH and FSH raised in response. |
| Sekundär hypogonadism | Low testosterone arising from the pituitary or hypothalamus, with LH and FSH low or inappropriately normal. |
| Dygnsrytm | The daily cycle in hormone levels. Testosterone peaks in the early morning and falls through the day. |
| Polycytemi | An over-concentrated blood count, tracked through hematocrit, which testosterone treatment can cause. |
Källor
- US Food and Drug Administration — Testosterone Information
- MedlinePlus Medical Encyclopedia (US National Library of Medicine) — Hypogonadism
- Schwartz J. Male Hypogonadism. StatPearls, NCBI Bookshelf, US National Library of Medicine
- Lincoff AM, Bhasin S, Flevaris P, et al. Cardiovascular Safety of Testosterone-Replacement Therapy. New England Journal of Medicine, 2023 (TRAVERSE)
- Szarpak L, Maslyk M, Kaminska H, et al. Testosterone replacement therapy and non-major adverse cardiovascular event safety signals. Kardiologia Polska, 2026
- Naelitz BD, Momtazi-Mar L, Vallabhaneni S, et al. Testosterone replacement therapy and spermatogenesis in reproductive age men. Nature Reviews Urology, 2025
- Nyamaah JA, Narinx N, Antonio L, Vanderschueren D. Use of calculated free testosterone in men: advantages and limitations. Current Opinion in Endocrinology, Diabetes and Obesity, 2024
- Anawalt BD, Handelsman DJ. Debate About the Free Testosterone Hypothesis: Useful Tool or Misguided Mirage? Journal of Clinical Endocrinology and Metabolism, 2025
Vidare läsning
- Complete blood count: understanding your results
- Fasting blood glucose levels: a complete guide to interpretation
- Estradiol: a key hormonal marker
- High testosterone in men: symptoms, causes and treatments
- Lågt testosteron hos kvinnor: orsaker, symtom och behandlingar
Förstå dina labresultat med AI DiagMe
A testosterone result rarely stands alone. It has to be read next to LH, FSH and SHBG, and against the time of day the sample was drawn. AI DiagMe turns those numbers into plain language so you can see what was measured and what still needs checking. It helps you understand your results; it does not diagnose anything and does not replace your doctor.
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