Low testosterone is a medical diagnosis that requires compatible symptoms or physical signs and consistently low blood-test results. In a 2026 statement, the Endocrine Society advised measuring testosterone with at least two early-morning blood tests. A single low result, an afternoon test, or an online symptom quiz cannot diagnose hypogonadism.
At a Glance
| What you notice | What it may mean |
|---|---|
| Persistently low sex drive | One of the more relevant symptoms of testosterone deficiency |
| Fewer spontaneous or morning erections | Worth discussing with a clinician, especially when libido is also low |
| Erectile dysfunction | Can occur with low testosterone, but may also result from vascular disease, diabetes, medications, stress, or other conditions |
| Infertility or low sperm count | May point to a reproductive hormone problem |
| Fatigue, low mood, or poor concentration | Possible, but not specific to low testosterone |
| Loss of muscle, body hair, or bone strength | Physical signs that can develop over time |
| One low testosterone result | Needs confirmation with repeat testing |
What Are the Symptoms of Low Testosterone?
The most useful symptoms in adult men are sexual changes, especially when they persist or occur together:
- Reduced sexual desire
- Fewer spontaneous or morning erections
- Difficulty getting or keeping an erection
- Infertility or a low sperm count
- Reduced sexual activity or satisfaction
Other possible signs include:
- Reduced energy
- Loss of muscle mass or strength
- Increased body fat
- Smaller testicles
- Reduced facial or body hair
- Enlarged or tender breast tissue
- Low mood, irritability, or difficulty concentrating
- Hot flashes, usually when testosterone is very low
- Low bone density or unexplained anemia
Low libido, erectile dysfunction, and fewer spontaneous erections are more useful clues than fatigue alone. Fatigue, mood changes, poor concentration, and reduced strength can also result from chronic stress, depression, sleep problems, or other medical conditions.
Can Fatigue Alone Mean You Have Low Testosterone?
Usually, no. Fatigue alone does not reliably indicate low testosterone. Poor sleep, obstructive sleep apnea, depression, thyroid disease, diabetes, medication effects, alcohol use, chronic illness, overtraining, and inadequate nutrition can cause similar symptoms.
Testing becomes more reasonable when fatigue occurs with specific sexual symptoms, such as persistently low libido, erectile dysfunction, or fewer spontaneous erections.
How Is Low Testosterone Diagnosed?
A clinician will usually:
- Review your symptoms, medical history, medications, sleep, and fertility plans.
- Order an early-morning total testosterone blood test.
- Repeat the test on a different morning if the result is low or borderline.
- Consider free testosterone or other hormone tests when appropriate.
- Investigate the cause instead of treating the number alone.
Testosterone levels are generally highest in the morning. The Endocrine Society recommends measuring testosterone on at least two separate early mornings, typically while fasting, with an accurate assay. The American Urological Association also recommends two early-morning total testosterone measurements before diagnosing testosterone deficiency.
What Testosterone Level Is Considered Low?
No single number diagnoses low testosterone in every man. Results depend on the laboratory method, reference range, age, symptoms, and overall health.
The American Urological Association commonly uses total testosterone below 300 ng/dL as a reasonable cut-off. However, a result below 300 ng/dL alone does not establish testosterone deficiency. The diagnosis also requires compatible symptoms or signs and consistently low results.
When total testosterone is near the lower end of the reference range, a clinician may measure free testosterone. This is the portion that is not tightly bound to blood proteins. Free testosterone can help when conditions such as obesity or altered sex hormone-binding globulin make total testosterone harder to interpret.
What Happens If the Test Is Low?
Further testing can help show whether the problem involves the testicles or the pituitary and hypothalamus, which control hormone production. Tests may include:
- Luteinizing hormone, or LH
- Follicle-stimulating hormone, or FSH
- Prolactin
- Thyroid tests
- Complete blood count
- Iron studies
- Semen analysis if fertility is a concern
- Pituitary imaging in selected cases
High LH and FSH can suggest a problem that originates in the testicles. Low or inappropriately normal LH and FSH can suggest a pituitary or hypothalamic cause. The tests you need depend on your testosterone results and symptoms.
What Can Cause Low Testosterone?
Low testosterone, also called male hypogonadism, can result from problems affecting the testicles, pituitary gland, or hypothalamus. Possible causes include:
- Testicular injury, infection, or cancer
- Chemotherapy or radiation treatment
- Pituitary disease
- Obesity
- Untreated obstructive sleep apnea
- Chronic liver or kidney disease
- Type 2 diabetes and other chronic illnesses
- Opioid pain medicines
- Corticosteroids and some hormone treatments
- Genetic conditions such as Klinefelter syndrome
- Severe illness, inadequate nutrition, or excessive physical stress
Testosterone can decline with age, but normal age-related change is not automatically testosterone deficiency. A diagnosis still requires relevant symptoms and consistently low blood-test results.
Are At-Home Testosterone Tests Accurate?
An at-home test may provide a preliminary result, but it should not be used alone to diagnose low testosterone or decide whether to start treatment. Testosterone levels vary with the time of day, illness, food intake, laboratory method, and normal day-to-day changes.
If you use an at-home kit, discuss the result with a healthcare professional and confirm it with properly timed laboratory testing. MedlinePlus states that a testosterone test alone cannot diagnose a health condition, even when the result is abnormal.
When Should You See a Doctor?
Make an appointment if you have persistent low libido, erectile problems, fewer spontaneous erections, infertility, unexplained loss of muscle or body hair, breast enlargement, or symptoms that affect your quality of life.
Headaches or vision changes alongside sexual or hormonal symptoms need prompt medical evaluation because pituitary disorders can affect testosterone production.
What to Do Next
Ask a primary care clinician, urologist, or endocrinologist about:
- Two early-morning total testosterone tests on separate days
- Whether fasting is required
- Whether free testosterone should be measured
- Tests for thyroid disease, diabetes, anemia, or other causes
- Fertility-preserving options if you are trying to conceive
Do not start testosterone replacement without a confirmed diagnosis. Testosterone therapy can suppress sperm production and may be unsuitable if you want children soon. Treatment also requires medical monitoring.