A man comes in with a lab report from a walk-in clinic. One line is highlighted: total testosterone, 310 ng/dL, flagged low. He has been told he needs weekly injections for the rest of his life.
The report has one number on it. It was drawn at 3 p.m. There is no SHBG, no LH, no FSH, no prolactin, and no second draw. That is not a diagnosis. It is a single data point that could mean four or five different things, and telling them apart is the entire job.
This post walks through what each value on a proper hormone panel measures, why they only make sense together, and what a defensible panel actually looks like.
Why one number cannot answer the question
Testosterone is not a static quantity. It follows a daily rhythm, peaking in the early morning and declining through the day. The size of that swing is large enough that the same man can produce a normal morning value and a low afternoon one on the same day.
That is why the standard, across the Endocrine Society and other major guidance, is confirmation on two separate early-morning samples paired with symptoms (https://pubmed.ncbi.nlm.nih.gov/29562364/). European guidance updated in 2026 restates the requirement for biochemical confirmation rather than acting on a single result (https://pubmed.ncbi.nlm.nih.gov/42177105/).
There is also short-term biological noise on top of the daily rhythm. Acute illness, poor sleep the night before, a very hard workout, and significant stress all move testosterone downward. A single draw during a rough week is not your baseline.
The practical rule we use: nothing gets treated on one number, and the number gets drawn before 10 a.m. after a reasonable night of sleep.
Total testosterone
This is the headline value, and it measures everything circulating: the fraction bound tightly to SHBG, the fraction bound loosely to albumin, and the small free fraction.
The problem with reading total alone is that most of it is not biologically available. The majority is bound to SHBG and essentially locked away. So the same total value means different things in two men with different binding protein levels.
Total testosterone is still the right first test. It is standardized, widely available, and reliable when measured by a good method. It just is not sufficient on its own in a meaningful minority of men, and knowing which minority requires the next value.
SHBG, the value that changes the interpretation
Sex hormone-binding globulin is the protein that binds testosterone in circulation. It is the most under-ordered test on this panel and often the most informative.
SHBG rises with: aging, hyperthyroidism, liver disease, some anticonvulsants, estrogen, and being underweight.
SHBG falls with: obesity, insulin resistance and type 2 diabetes, hypothyroidism, nephrotic syndrome, corticosteroids, and growth hormone.
Here is why it matters clinically. A man with high SHBG can have a total testosterone comfortably in the normal range while his free testosterone, the part that actually reaches tissue, is low. He has real symptoms and a normal-looking report. Conversely, a man with obesity and low SHBG can have a total testosterone that reads low while his free level is adequate, and treating him with testosterone would be solving the wrong problem.
Research on SHBG in hypogonadism and infertility has emphasized exactly this interpretive role (https://pubmed.ncbi.nlm.nih.gov/28087298/). If you have a normal total testosterone and clear symptoms, or a low total testosterone and significant obesity, SHBG is the test that clarifies things.
Free testosterone, and why the method matters
Free testosterone is the unbound, biologically active fraction. It is typically 1 to 3 percent of total.
This is where labs diverge in quality, and it is worth knowing which one yours used. Direct analog immunoassays for free testosterone are inexpensive, widely used, and widely criticized for poor accuracy. The more defensible options are equilibrium dialysis, considered the reference method, and calculated free testosterone derived from total testosterone, SHBG, and albumin. Reviews of testosterone measurement have been explicit that assay methodology substantially affects whether a free testosterone result can be trusted (https://pubmed.ncbi.nlm.nih.gov/35927159/), and measurement technology continues to develop (https://pubmed.ncbi.nlm.nih.gov/42058326/).
Practically: if a free testosterone result does not fit the clinical picture, the first question is not what is wrong with the patient. It is what method the lab used.
LH and FSH, the values that locate the problem
These two are produced by the pituitary. LH tells the testes to make testosterone. FSH drives sperm production. Together they tell us where in the chain something has gone wrong, and this determines everything that follows.
Low testosterone with high LH and FSH is primary hypogonadism. The pituitary is signaling hard and the testes are not responding. The problem is in the testes. Causes include prior injury, infection, chemotherapy, undescended testes, and genetic conditions such as Klinefelter syndrome.
Low testosterone with low or inappropriately normal LH and FSH is secondary hypogonadism. The signal itself is missing. Causes include obesity, obstructive sleep apnea, opioids, anabolic steroid use, significant systemic illness, a prolactinoma, and other pituitary problems.
That distinction has direct consequences. Secondary hypogonadism is frequently reversible by treating the cause, and it is also the group in which medications that stimulate the axis, rather than replacing testosterone, can work. Clomiphene and enclomiphene raise LH and FSH and preserve fertility, and their evidence base is specifically in secondary hypogonadism (https://pubmed.ncbi.nlm.nih.gov/23875626/, https://pubmed.ncbi.nlm.nih.gov/34933414/). In primary hypogonadism, stimulating an axis that is already maximally stimulated does nothing. Our post on clomiphene and enclomiphene covers that pathway in detail.
A clinic that does not draw LH and FSH cannot know which of these you have, and therefore cannot know whether it is offering you the right treatment.
The rest of a proper panel
Prolactin. An elevated prolactin can suppress the whole axis and can indicate a pituitary tumor. Rare, but this is the finding you do not want to discover two years into injections.
Estradiol. Testosterone converts to estradiol, and the ratio matters for symptoms including breast tenderness and mood. It also matters for monitoring once on therapy.
Complete blood count. Baseline hematocrit before starting therapy, because testosterone raises it and that is one of the main monitored risks.
Comprehensive metabolic panel and A1c. Insulin resistance is one of the most common drivers of low SHBG and secondary hypogonadism, and it is treatable.
Thyroid function. Thyroid disease moves both SHBG and symptoms, and it is frequently the actual explanation for the fatigue that brought you in.
PSA in men over 40. Baseline before starting therapy.
Iron studies and vitamin D where the clinical picture supports it.
Roughly half the purpose of this panel is not to confirm low testosterone. It is to find the reversible thing causing it, or the different condition explaining your symptoms entirely. Our post on male fatigue and when it is not low testosterone covers that differential.
Putting it together
Four common patterns, and what each one means:
Low total, low free, high LH and FSH. Primary hypogonadism. Testosterone replacement is the main option; fertility-sparing stimulation will not work.
Low total, low free, low or normal LH and FSH. Secondary hypogonadism. Look hard for the cause: weight, sleep apnea, opioids, prior anabolic steroid use, prolactin, pituitary. Reversible causes get treated first, and fertility-sparing options are on the table.
Normal total, low free, high SHBG. The pattern that gets dismissed. Symptoms are real, the headline number looks fine, and free testosterone is the value that explains it.
Low total, normal free, low SHBG, obesity present. Common and frequently overtreated. Weight and metabolic health are usually the intervention, not testosterone.
Everything normal, symptoms present. Also common, and the honest answer is that the problem is somewhere else. Sleep, thyroid, iron, depression, alcohol, and medication effects account for a great deal of the fatigue and low libido that gets attributed to testosterone.
What we do with your panel
We draw before 10 a.m., twice, on separate days. We order SHBG, LH, and FSH as standard rather than as an add-on. We check what method your lab uses for free testosterone. We look for reversible causes before we reach for a prescription, and we will tell you when the answer is that your testosterone is fine and something else is going on.
If you are already on therapy and your clinic has never drawn an LH, or you have a single flagged number and a recommendation for lifelong treatment, a second opinion is reasonable. Our overview of testosterone replacement therapy covers what appropriate treatment and monitoring look like.
Book a visit through our men's health services at nomibeach.health or call (786) 744-5152. Bring whatever labs you already have. Often the answer is already in them, one test short.
Frequently Asked Questions
- Why does my testosterone need to be measured in the morning?
- Testosterone follows a daily rhythm and is highest in the early morning. An afternoon draw in a man with entirely normal production can read low, which is how a great many people end up on lifelong therapy they never needed. Guidance is consistent that confirmation requires early-morning samples on separate days.
- What is the difference between total and free testosterone?
- Total testosterone measures everything in your blood, most of which is bound to proteins and not available to your tissues. Free testosterone is the small unbound fraction that is actually active. When the binding protein SHBG is abnormal, total and free can tell opposite stories, which is exactly when free matters (https://pubmed.ncbi.nlm.nih.gov/35927159/).
- Why does SHBG matter?
- Sex hormone-binding globulin determines how much of your total testosterone is locked up. It rises with age, hyperthyroidism, liver disease, and some medications, and it falls with obesity, insulin resistance, and hypothyroidism. A high SHBG can make a normal total testosterone look adequate when the free level is genuinely low (https://pubmed.ncbi.nlm.nih.gov/28087298/).
- What do LH and FSH tell you?
- They tell us where the problem is. Low testosterone with high LH and FSH points to the testes themselves. Low testosterone with low or inappropriately normal LH and FSH points upstream to the pituitary or hypothalamus. That distinction changes the entire workup and the treatment options available to you.
- How accurate is a free testosterone result?
- It depends entirely on how the lab measured it. Direct analog immunoassays for free testosterone are widely regarded as unreliable. Calculated free testosterone from total testosterone, SHBG, and albumin, or equilibrium dialysis, are the more defensible approaches (https://pubmed.ncbi.nlm.nih.gov/35927159/). We check which method your lab used.
- Is a single low result enough to diagnose low testosterone?
- No. Confirmation on two separate early-morning draws, paired with symptoms that actually fit, is the standard. European guidance published in 2026 reiterates the requirement for biochemical confirmation rather than a single value (https://pubmed.ncbi.nlm.nih.gov/42177105/).
- What else should be on the panel besides testosterone?
- At minimum SHBG, LH, FSH, prolactin, a complete blood count, a metabolic panel, and often estradiol, thyroid function, iron studies, and A1c. Half the value of the panel is ruling out the reversible causes of low testosterone rather than confirming the number.
Sources
- Guzelce EC, Eyupoglu D, Torlak Z, et al. Accurate measurement of total and free testosterone levels for the diagnosis of androgen disorders. Best Pract Res Clin Endocrinol Metab (2022);36(4):101683.
- Corona G, et al. EAU Guidelines on Sexual and Reproductive Health: A Summary of the 2026 Recommendations for Measurement and Biochemical Confirmation of Hypogonadism. Eur Urol Focus (2026).
- Ring J, Welliver C, Parenteau M, et al. The Utility of Sex Hormone-Binding Globulin in Hypogonadism and Infertile Males. J Urol (2017);197(5):1326-1331.
- Bhasin S, Brito JP, Cunningham GR, et al. Testosterone Therapy in Men with Hypogonadism: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab (2018);103(5):1715-1744.
- American Urological Association. Testosterone Deficiency Guideline (2018, amended 2024).
- Wiehle RD, Cunningham GR, Pitteloud N, et al. Testosterone Restoration by Enclomiphene Citrate in Men with Secondary Hypogonadism. BJU Int (2013);112(8):1188-1200.
- Huijben M, Lock MTWT, et al. Clomiphene Citrate for Men with Hypogonadism: A Systematic Review and Meta-Analysis. Andrology (2022);10(3):451-469.
- Han S, et al. Development of Free Testosterone Chemiluminescence Detection Kit and Its Clinical Application. J Anal Methods Chem (2026);2026:5165899.
