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Suffering from lack of energy, reduced sex drive or lack of training results often raises the question of testosterone deficiency. A blood test can provide important answers, but a diagnosis always requires both clear symptoms and repeated low morning values. Since hormone levels are affected by sleep, stress, obesity and exercise, the test is sensitive to temporary dips. In case of borderline values, the measurement is often supplemented with more tests, such as SHBG and pituitary hormones, to see the active amount of testosterone. However, low values do not automatically mean that drug treatment is needed - lifestyle changes or investigation of underlying causes are often the first step.
Feeling unusually tired, losing sex drive, having less energy at the gym or noticing that your recovery has slowed down often raises the same question: could it be low testosterone? A testosterone test with a venous blood sample can provide important information, but the answer is rarely as simple as a single value. Testosterone varies throughout the day, is affected by sleep, weight, illness and medication, and always needs to be interpreted together with symptoms and sometimes more analyses. That's why it's important to understand both what the test shows - and what it doesn't show.
Testosterone test - Find out your level with a venous blood sample
Testosterone is a sex hormone that is found in both men and women, but the levels are significantly higher in men. The hormone is mainly formed in the testicles in men and in smaller amounts in the ovaries and adrenal glands in women. Testosterone affects, among other things, sex drive, erectile function, sperm production, muscle mass, bone density, energy level and mood. If testosterone deficiency is suspected, a blood test is the medical basis for investigation, but guidelines emphasize that the diagnosis should only be made if you have both typical symptoms and repeated low morning values.
When is a testosterone test relevant?
A testosterone test is most relevant when there are symptoms consistent with testosterone deficiency, also called hypogonadism. It is not primarily about “optimizing” a value, but about trying to understand a possible medical cause of symptoms.
Common symptoms that may justify testing are:
- reduced sex drive
- fewer spontaneous or morning erections
- erectile difficulties
- fatigue or reduced energy
- depressed mood or reduced drive
- reduced muscle mass or strength
- increased fat mass, especially abdominal obesity
- impaired fertility
- reduced beard growth or other body hair
- fragile bones or fractures after minor trauma
Some symptoms are more specific than others. Reduced sex drive and fewer morning erections are medically more important than more general complaints such as fatigue, as fatigue can also be caused by stress, lack of sleep, depression, iron deficiency, thyroid disease or high workload. Very low testosterone levels can cause reduced sex drive, reduced energy, depression and erection difficulties.
How is a venous blood test for testosterone done?
A venous blood test means that the sample is taken from a vein in the arm by trained personnel. It is the most common and most reliable method for analyzing testosterone in the blood. The test itself only takes a few minutes.
Since testosterone varies throughout the day, the time of day is important. Levels are usually highest in the morning and lower later in the day. Therefore, it is recommended that total testosterone be tested first in the morning, often in a fasting state, and that a low value should be confirmed with a new morning test at another time.
This is a good idea to keep in mind before taking the test:
- Take the test in the morning, preferably early
- Follow the instructions you receive about fasting
- Avoid testing yourself when you are acutely ill
- Inform about the medications and supplements you are using
- Tell us if you are using testosterone, anabolic steroids or fertility treatment
Temporary factors can affect the result. Hard training, lack of energy, lack of sleep, acute infection and certain medications can temporarily cause lower testosterone. Opioids, cortisone preparations and previous or ongoing use of anabolic androgenic steroids can also disrupt the body's own hormone production.
In some cases, simply measuring total testosterone is not enough. Then you may also need to analyze:
- SHBG – a transport protein that binds testosterone in the blood
- free testosterone – the proportion of testosterone that is not bound and biologically active
- LH and FSH – hormones from the pituitary gland that help determine whether the cause is in the testicles or higher up in the hormonal system
- prolactin – can be elevated in certain hormonal disorders
- sometimes also blood status, PSA, liver tests, blood suger and thyroid tests depending on the question
This is especially important if total testosterone is in the borderline range or if SHBG is suspected to be affected, for example in cases of obesity, old age, liver disease or certain medications.
What does a testosterone test result mean?
The short answer is: it depends. A testosterone value must always be interpreted in context. Reference intervals can differ between laboratories, and a value that is normal for one person may not be normal for another. Therefore, you should not self-diagnose based on a single number.
Medically, two things are usually required to talk about testosterone deficiency in men:
- symptoms or clinical signs that are consistent with a deficiency
- repeated low testosterone values in the morning test
It is therefore not enough to just have symptoms, and it is not enough to have a single low test result.
A low value can be due to different types of causes:
- Primary hypogonadism – the testicles produce too little testosterone.
- Secondary hypogonadism – the signals from the pituitary gland or hypothalamus do not work properly.
- Functionally low testosterone – levels are affected by, for example, obesity, chronic illness, stress, lack of sleep or medication.
This is an important distinction. If low testosterone levels are largely caused by, for example, obesity, poor sleep or untreated sleep apnea, the underlying problem can sometimes improve without testosterone treatment being the right first step. Some causes, such as obesity, may be reversible. However, low testosterone levels can also be seen in cases such as obesity, pituitary diseases, inflammatory conditions and drug effects.
A testosterone value in the lower part of the laboratory reference range does not automatically mean testosterone deficiency. If there are no clear symptoms, a value within the reference range usually indicates a deficiency. However, in the case of pronounced symptoms, borderline values or factors that affect SHBG, additional hormone tests may be required to investigate whether the free, active amount of testosterone is too low.
Common causes of low testosterone – and why they should be investigated
Low testosterone is not a disease in itself, but often a sign that something is affecting the body's hormonal balance. Therefore, a testosterone test is primarily a tool to find the right explanation.
Possible causes include:
- increasing age, with gradually decreasing levels
- obesity and metabolic disease
- type 2 diabetes
- chronic disease or inflammatory conditions
- sleep apnea
- drugs, especially opioids and certain hormone-affecting drugs
- pituitary disease
- congenital conditions, such as Klinefelter's syndrome
- injury or disease of the testicles
- previous use of anabolic steroids
Although testosterone slowly decreases over the years, it is important not to dismiss clear symptoms as "normal aging". At the same time, treatment should not be initiated lightly. You should first ensure the diagnosis and try to understand the cause.
Here are some typical situations where a testosterone test is often relevant:
- The man in his 40s and 50s who has lost sex drive, energy and exercise results despite an unchanged lifestyle.
- The younger man with fertility problems where testosterone, LH and FSH can provide important information about hormonal function.
- The person with obesity and pronounced daytime fatigue where low testosterone can coexist with sleep apnea and metabolic effects.
- The man with erectile dysfunction where testosterone is sometimes part of the explanation, but where vascular disease, diabetes, stress and psychological factors are also common causes.
That is why testosterone tests can be a valuable complement to other analyses in a broader health check, such as blood sugar, blood lipids, liver tests and thyroid values.
What happens if testosterone is low?
If the test shows low testosterone, the next step is not automatically treatment. First, the result needs to be confirmed and interpreted together with symptoms, medical history and supplementary tests. In some cases, further investigation may be needed, for example of LH, FSH and prolactin, and sometimes even MRI of the pituitary gland if a central hormonal disorder is suspected.
Treatment depends on the cause:
- lifestyle measures for obesity, lack of sleep or metabolic illness
- treatment of the underlying disease
- adjustment of medications that affect hormone balance
- testosterone treatment in selected cases with clear symptoms and confirmed deficiency
Testosterone treatment can improve symptoms in the right patient, but is not risk-free. Possible side effects and risks include elevated blood counts, acne, effects on fertility, breast effects and the need for monitoring of blood counts and sometimes prostate-related parameters. Treatment should be monitored regularly and men who want to preserve fertility need special assessment, as testosterone treatment can reduce sperm production.
A common question is: “Can I start taking testosterone if I just feel tired?”
The answer is usually no. Fatigue alone is not enough for a diagnosis, and there are many other, more common and sometimes more important causes to rule out first. Therefore, it is wise to see the testosterone test as part of a comprehensive medical assessment, not as an isolated “yes or no” test.
