How Is Low Testosterone Diagnosed?
Written by YiQiu Hu, NMD
Arizona-licensed naturopathic physician and virtual concierge medicine provider
Published August 2026 | Medically reviewed August 2026
Low testosterone is diagnosed using both symptoms and laboratory testing. A single low testosterone result is generally not enough to establish testosterone deficiency.
For most men, the evaluation begins with a discussion of symptoms and medical history followed by an early-morning total testosterone blood test. If the testosterone level is low, the test is usually repeated on a different morning to confirm that the finding is persistent.
Professional guidelines emphasize that testosterone deficiency should generally be diagnosed when a man has symptoms or signs consistent with low testosterone together with repeatedly low testosterone levels.
If you would like a broader overview of the condition, read our physician guide to Low Testosterone in Men: Symptoms, Diagnosis, and Treatment Options.
What Symptoms May Lead to Testosterone Testing?
Testing is usually considered when a man has symptoms or clinical findings that could be associated with testosterone deficiency.
These may include:
Reduced sex drive
Fewer spontaneous or morning erections
Erectile dysfunction
Reduced energy
Decreased muscle mass or strength
Increased body fat
Difficulty concentrating
Changes in mood or motivation
Reduced exercise performance
Infertility
Decreased body hair
Breast enlargement or tenderness
Reduced bone density
Unexplained anemia
However, these symptoms are not specific to low testosterone.
Fatigue, changes in sexual function, low motivation, weight changes, poor sleep, and difficulty concentrating may also occur with thyroid disorders, sleep apnea, depression, obesity, chronic illness, medication effects, nutritional problems, stress, and many other conditions.
That is why testosterone deficiency should not be diagnosed based on symptoms alone. The Endocrine Society specifically emphasizes that symptoms must be accompanied by consistently low testosterone measurements.
How Is Testosterone Tested?
The primary laboratory test used during an initial evaluation is usually total testosterone.
Testosterone levels naturally fluctuate throughout the day and are generally highest earlier in the day. Because of this variation, professional guidelines recommend measuring testosterone in the morning.
The Endocrine Society recommends confirming suspected hypogonadism with repeat morning fasting total testosterone measurements rather than relying on a single test.
In practical terms, a typical evaluation may involve:
An initial early-morning testosterone measurement.
A second early-morning measurement on a different day if the first result is low.
Additional laboratory testing when needed to clarify the diagnosis or determine why testosterone is low.
Testing during an acute illness or other temporary physiologic stress may sometimes produce results that do not reflect a patient's usual hormone status, so the clinical circumstances surrounding the test also matter.
Why Does Testosterone Usually Need to Be Tested Twice?
Testosterone is not a completely stable number.
Levels can vary because of:
Time of day
Sleep patterns
Acute illness
Calorie intake
Certain medications
Significant changes in body weight
Other medical conditions
Normal biological variation
Differences among laboratory assays
For this reason, one unexpectedly low testosterone measurement does not necessarily mean that a man has testosterone deficiency.
Current Endocrine Society guidance recommends at least two early-morning testosterone measurements when diagnosing hypogonadism.
Repeating the test reduces the likelihood that treatment decisions are based on a temporary or inaccurate result.
What Testosterone Level Is Considered Low?
There is no single laboratory number that should be interpreted completely independently of the patient.
The American Urological Association uses a total testosterone level below 300 ng/dL as a reasonable cutoff supporting a diagnosis of testosterone deficiency.
However, a testosterone result below 300 ng/dL does not automatically mean that testosterone replacement therapy is appropriate.
The result still needs to be considered alongside:
Symptoms
Repeat testing
The laboratory's reference range
Age and health history
Medications
Other hormone levels
Possible reversible causes
Fertility goals
Overall clinical findings
Likewise, a man with a borderline testosterone level may occasionally require additional evaluation rather than being classified simply as having a "normal" or "low" result.
The goal is to diagnose the patient, not simply treat a laboratory number.
Do Free Testosterone and SHBG Need to Be Tested?
Sometimes.
Most initial evaluations begin with total testosterone, but free testosterone and sex hormone-binding globulin (SHBG) can provide additional information in selected patients.
Most circulating testosterone is attached to proteins in the bloodstream, particularly SHBG and albumin. Only a small portion circulates as free testosterone.
Changes in SHBG can therefore influence the relationship between total testosterone and the amount of testosterone available to tissues.
A physician may consider evaluating free testosterone or SHBG when:
Total testosterone is borderline
Symptoms and total testosterone results do not seem to match
A medical condition may affect SHBG
Additional clarification of testosterone status is necessary
The Endocrine Society recommends using accurate total and free testosterone assays and appropriate reference ranges when free testosterone testing is indicated.
Not every man needs an extensive hormone panel, however. Laboratory testing should be selected according to the individual clinical situation.
What Happens If Low Testosterone Is Confirmed?
Confirming that testosterone is low is only part of the evaluation.
The next question is:
Why is the testosterone low?
Testosterone production depends on communication among the hypothalamus, pituitary gland, and testes.
The brain signals the pituitary gland, which produces hormones called luteinizing hormone (LH) and follicle-stimulating hormone (FSH). These hormones help regulate testicular testosterone production and reproductive function.
Once testosterone deficiency has been confirmed, LH and sometimes FSH can help determine whether the problem appears to originate primarily from the testes or from the hormonal signaling system in the brain and pituitary gland.
The Endocrine Society specifically recommends measuring LH and FSH to distinguish primary hypogonadism from secondary hypogonadism.
What Is Primary Hypogonadism?
Primary hypogonadism means the testes are not producing an appropriate amount of testosterone despite receiving hormonal signals from the brain.
In this situation, testosterone is generally low while LH and sometimes FSH may be elevated because the pituitary is attempting to stimulate the testes more strongly.
Possible causes can include certain genetic disorders, testicular injury, previous chemotherapy or radiation, infection, or other conditions affecting testicular function.
What Is Secondary Hypogonadism?
Secondary hypogonadism occurs when the testes may be capable of producing testosterone, but they are not receiving adequate stimulation from the hypothalamus or pituitary gland.
Testosterone may be low while LH and FSH are low or inappropriately normal.
Depending on the patient's history and laboratory pattern, additional evaluation may then be appropriate.
The AUA notes that men with hypogonadotropic hypogonadism may sometimes benefit from additional testing such as prolactin, iron studies, or pituitary imaging.
What Other Blood Tests May Be Ordered?
There is no single testosterone laboratory panel that every man needs.
Depending on the clinical situation, additional testing may include:
LH
FSH
Prolactin
SHBG
Free testosterone
Thyroid testing
Complete blood count
Metabolic testing
Iron studies
Other pituitary hormones
A physician may also evaluate conditions that can contribute to low testosterone or produce similar symptoms.
These can include obesity, metabolic disease, sleep disorders, thyroid dysfunction, chronic illness, medication effects, and other endocrine conditions.
This broader approach is one reason laboratory testing should be interpreted together with symptoms and medical history rather than in isolation.
Is a Pituitary MRI Needed to Diagnose Low Testosterone?
Usually not.
Most men being evaluated for low testosterone do not automatically need brain imaging.
A pituitary MRI may be considered when the laboratory pattern or symptoms suggest a possible pituitary or hypothalamic disorder.
For example, additional investigation may be appropriate in selected patients with markedly abnormal testosterone and gonadotropin levels, elevated prolactin, other pituitary hormone abnormalities, or concerning neurological symptoms.
The appropriate evaluation depends on the individual circumstances rather than a standard imaging protocol for everyone.
Can Obesity, Medications, or Other Conditions Lower Testosterone?
Yes.
Low testosterone measurements do not always indicate permanent failure of testosterone production.
Testosterone may be influenced by conditions such as:
Obesity
Significant calorie restriction
Poorly controlled chronic disease
Sleep disorders
Certain medications
Opioid use
Corticosteroid use
Pituitary disorders
Severe illness
The Endocrine Society's 2026 statement specifically emphasizes evaluating reversible contributors such as obesity and medication effects rather than assuming every low testosterone measurement requires testosterone replacement therapy.
Identifying these factors can significantly change the treatment plan.
Does a Low Testosterone Result Mean I Need TRT?
No.
A low testosterone result identifies a finding that requires interpretation. It does not automatically establish that testosterone or hormone replacement therapy should be started.
Before recommending treatment, a physician may consider:
Whether symptoms are actually consistent with testosterone deficiency
Whether testosterone was repeatedly low
Why testosterone is low
Whether reversible causes can be treated
Cardiovascular and general medical history
Hematocrit and blood counts
Prostate considerations when appropriate
Sleep apnea
Current medications
Fertility plans
Potential benefits and risks of treatment
This evaluation is particularly important because external testosterone can suppress the hormonal signals responsible for sperm production.
Men who may want biological children should therefore discuss fertility goals before starting testosterone therapy.
You can learn more about the overall treatment process in our Hormone Replacement Therapy Resource Library.
Can Low Testosterone Be Diagnosed Through Telemedicine?
Much of the initial evaluation can often be performed through telemedicine.
A physician can review:
Symptoms
Medical history
Medications
Previous laboratory results
Fertility goals
Relevant health conditions
Treatment history
Laboratory testing can then be ordered through an appropriate laboratory.
Some patients may require an in-person physical examination, imaging, specialist referral, or additional testing depending on the findings.
At Ask Dr. Hu, hormone consultations are available for eligible patients throughout Arizona through secure telemedicine, with in-person evaluation available or recommended when clinically appropriate.
The Bottom Line
Low testosterone is generally diagnosed through a combination of compatible symptoms and repeatedly low testosterone levels, not from one blood test or symptoms alone.
An appropriate evaluation typically begins with an early-morning total testosterone measurement. If the result is low, another morning measurement is usually obtained to confirm it.
If testosterone deficiency is confirmed, additional tests such as LH, FSH, free testosterone, SHBG, prolactin, or other laboratory studies may be used when appropriate to determine the underlying cause.
The most important question is therefore not simply, "Is my testosterone number low?"
It is:
"Do my symptoms, repeated laboratory results, and overall medical evaluation support a true diagnosis of testosterone deficiency—and if so, why is it happening?"
That distinction helps ensure that testosterone therapy is used for appropriately evaluated patients rather than treating an isolated laboratory result.
Evidence-Based Medical References
This article was developed using current clinical guidance and authoritative medical sources, including the Endocrine Society Clinical Practice Guideline on Testosterone Therapy in Men With Hypogonadism, the American Urological Association Testosterone Deficiency Guideline, and current U.S. Food and Drug Administration information about testosterone therapy.
The Endocrine Society reaffirmed in July 2026 that diagnosis should be based on appropriate symptoms together with consistently low, accurately measured testosterone concentrations and that early-morning testing should generally be repeated before establishing hypogonadism.
Medical guidance, laboratory methods, and testosterone prescribing information may change as new evidence becomes available. Individual diagnosis and treatment decisions should be made with a qualified healthcare professional familiar with the patient's complete medical history.
About the Author
YiQiu Hu, NMD
Dr. YiQiu Hu is an Arizona-licensed naturopathic physician and founder of Ask Dr. Hu. His clinical work focuses on concierge medicine, preventive healthcare, health optimization, laboratory evaluation, medical weight management, hormone care, integrative pain management, and individualized treatment planning.
At Ask Dr. Hu, Dr. Hu provides personalized medical care for patients throughout Arizona with an emphasis on thorough evaluation, clear explanations, evidence-informed treatment options, and ongoing physician-patient relationships.
This article is provided for general educational purposes and does not replace individualized medical evaluation, diagnosis, or treatment.