- Total testosterone is the wrong number to judge this on. Most of it is bound to SHBG and biologically unavailable. Free testosterone is what reaches the receptor.
- Insulin suppresses SHBG, which is why two men with identical total testosterone can have very different free levels — and why metabolic health drives this more than age does.
- Most men can raise their own production substantially with sleep, resistance training, correcting deficiencies and reducing the aromatase load.
- TRT shuts down your own production. That is a real trade-off worth understanding before you start, not after.
- The levels most clinics call normal are population averages, drawn from a population that is heavier and more metabolically unwell every decade.
Why total testosterone tells you almost nothing on its own
What I see almost every week is a man told his testosterone is fine at 480, or told it is low at 320, on the basis of a single number that cannot answer the question.
Roughly 98 percent of the testosterone circulating in your blood is bound — most of it to sex hormone binding globulin, some to albumin. Bound testosterone cannot enter a cell. Only the free fraction, around two percent, actually does anything.
So the man with a total of 480 and an SHBG of 22 has considerably more usable hormone than the man with a total of 620 and an SHBG of 62. Judge either of them on total alone and you will reach the wrong conclusion.
Here is what makes this clinically urgent rather than academic: insulin suppresses SHBG. Metabolic dysfunction changes the ratio directly. Which means a man's testosterone picture is a metabolic picture as much as a hormonal one — and treating it as purely hormonal is why so many men end up on replacement they might not have needed.
How low testosterone actually develops
Notice that the starting point is metabolic rather than hormonal. That is why correcting sleep and insulin so often raises testosterone without a prescription.
The panel that actually answers the question
The LH result is the one that changes the plan most. Low testosterone with low LH means the signal from the brain has dropped — usually from sleep debt, chronic stress, insulin resistance or excess body fat, and usually reversible. Low testosterone with high LH means the brain is shouting and the testicle is not answering, which is a different conversation.
When testosterone replacement is genuinely the right call
There are men who need it, and when that is true we say so and work with them or their prescribing physician to get it right.
Primary testicular failure, where LH is elevated and the testicle cannot respond. Genuinely depleted free testosterone that has not moved after six months of proper foundational work. Significant symptoms with a full panel confirming the picture. These warrant the conversation.
What every man should understand before starting: exogenous testosterone suppresses your own production. The brain sees adequate hormone, stops sending LH, and the testicles reduce output. That is usually reversible early on and less reliably so after years. It also affects fertility, which matters enormously to some men and not at all to others — but it should be a decision rather than a surprise.
When it is used, the details matter. Smaller more frequent injections produce steadier levels than large fortnightly doses. Haematocrit needs monitoring, because testosterone raises it. And we are cautious about pellets, because the dose cannot be adjusted for months and supraphysiological levels are a recognised problem — when a man arrives with a total of 1,400, pellets are very often why.
The ten levers that raise your own testosterone
Ranked by how much difference each makes and how often the problem sits there.
Fix Sleep First
The most powerful lever and the most ignored. Testosterone is released predominantly during deep sleep, and research has shown that restricting healthy young men to five hours a night for one week reduced daytime testosterone by ten to fifteen percent — the equivalent of ageing them a decade. No supplement compensates for this.
What the evidence showsSleep restriction to five hours nightly for one week reduced daytime testosterone by 10 to 15 percent in healthy young men in a controlled study published in JAMA. Testosterone release is concentrated during sleep.Bring Insulin Down
Insulin suppresses SHBG and drives aromatase, the enzyme converting testosterone to estrogen. Correcting insulin resistance raises free testosterone through two mechanisms at once, and it is why metabolic work often does more here than anything hormonal.
What the evidence showsAdipose tissue expresses aromatase, converting testosterone to estradiol. Visceral fat therefore both lowers testosterone and raises estrogen, and the relationship is bidirectional and self-reinforcing.Resistance Train Properly
Heavy compound lifting produces an acute hormonal response and, more importantly, builds the muscle that improves insulin sensitivity. Excessive endurance volume does the opposite — chronically elevated cortisol suppresses production.
What the evidence showsResistance training acutely raises testosterone and, more importantly, improves androgen receptor density and insulin sensitivity. Compound movements produce a larger hormonal response than isolation work.Lose Visceral Fat Specifically
Adipose tissue contains aromatase, which converts testosterone into estrogen. More visceral fat means more conversion, lower testosterone and higher estradiol simultaneously. This is a loop, and breaking it changes both numbers.
What the evidence showsInsulin resistance suppresses SHBG production and is independently associated with lower total testosterone across large cohorts. Correcting insulin frequently raises testosterone without direct hormonal intervention.Correct Vitamin D
Vitamin D receptors sit on the cells that produce testosterone, and deficiency is associated with lower levels. This is inexpensive, frequently deficient even in Tennessee, and worth correcting before anything more involved.
What the evidence showsZinc is required for testosterone synthesis and for the enzyme that converts testosterone to dihydrotestosterone. Deficiency is associated with hypogonadism and corrects with repletion in deficient men.Get Zinc and Magnesium Right
Zinc is directly required for testosterone synthesis and deficiency measurably lowers levels. Magnesium reduces SHBG binding, which raises the free fraction without changing the total. Both measured intracellularly, not in serum.
What the evidence showsVitamin D receptors are present in Leydig cells, and randomised placebo-controlled supplementation in deficient men has shown increases in total and free testosterone.Manage Cortisol
Cortisol and testosterone are functionally opposed — sustained stress suppresses production directly at the level of the brain. A man under genuine chronic stress will not out-supplement it, and this is frequently the missing piece in someone doing everything else right.
What the evidence showsCortisol and testosterone are functionally antagonistic, and sustained stress suppresses gonadotropin-releasing hormone pulsatility at the hypothalamic level, reducing downstream LH and testosterone.Reduce Aromatase Load
Alcohol, excess body fat and some medications all increase conversion to estrogen. Cruciferous vegetables support estrogen clearance. This is not about crushing estrogen — men need it — it is about correcting a ratio that has drifted.
What the evidence showsSeveral common exposures including phthalates and bisphenol A have documented anti-androgenic activity in human and experimental studies, and urinary metabolite levels correlate inversely with testosterone in population data.Check the Thyroid
Hypothyroidism produces fatigue, low libido, weight gain, low mood and poor recovery — every symptom on the low testosterone list. Treating the testosterone while missing this is the most common diagnostic error we correct.
What the evidence showsAshwagandha has randomised placebo-controlled trial evidence for increasing testosterone and improving sperm parameters, with effect sizes larger in stressed and subfertile populations.Consider Peptides Before Replacement
For some men, a growth hormone secretagogue improves sleep quality, body composition and recovery enough that the testosterone picture improves on its own. Not a testosterone therapy, but often a useful step before one.
What the evidence showsThe Endocrine Society clinical practice guideline recommends testosterone therapy for men with consistently low morning levels and clinical symptoms, with monitoring of haematocrit, PSA and lipids during treatment.What patients commonly experience under our care
When patients receive the proper guidance, here is what they commonly experience under our care.
- Weeks 2–4 — sleep and morning energy. Once sleep quality improves and blood sugar stabilises, men describe waking properly for the first time in years. This is usually the first change and it arrives before any hormone number moves.
- Weeks 4–8 — drive, mood and libido. Downstream of better sleep and improving free testosterone. Men frequently report motivation returning before anything physical changes, which is what you would expect from a hormone that acts substantially on the brain.
- Weeks 8–12 — the panel moves. Free testosterone climbing toward 15–25 ng/dL. SHBG normalising. Fasting insulin falling. Estradiol settling into 20–30 pg/mL. We retest here so the decision about replacement is made on evidence.
- Months 3–6 — body composition and strength. Muscle mass and strength improve, visceral fat falls, and the aromatase load drops with it. For a meaningful number of men this is the point at which replacement stops being necessary.
If you have been handed a prescription on the strength of one number, or told you are fine when you know you are not, schedule a consultation. My team will run the full picture, raise what can be raised naturally, and tell you honestly if replacement is the right call. Care from people who will not stop until the root cause of every one of your health issues has been found and addressed.
Total, free, SHBG, estradiol, LH, insulin and thyroid — read together, because separately they cannot answer the question.
Common questions
What is a normal testosterone level for a man?
Most labs report a reference range of roughly 300 to 1,000 ng/dL for total testosterone, but that range comes from a population that has grown heavier and more metabolically unwell every decade. We treat 600 to 900 as optimal for total, 15 to 25 ng/dL for free testosterone, and SHBG between 20 and 45 — because free testosterone is what actually reaches your cells.
Can I raise testosterone naturally without TRT?
In most cases we see, substantially yes. Sleep is the largest lever — restricting healthy young men to five hours a night for one week has been shown to reduce daytime testosterone by ten to fifteen percent. Correcting insulin resistance, losing visceral fat, resistance training, and fixing vitamin D, zinc and magnesium deficiency together produce a meaningful change in most men.
Is there a low testosterone doctor near Nashville?
Yes. We are at 329 S. Royal Oaks Blvd in Franklin, Tennessee, about twenty minutes south of downtown Nashville and minutes from Brentwood and Cool Springs. We run the full male panel including SHBG, free testosterone, sensitive estradiol, LH, fasting insulin and a complete thyroid cascade before any treatment decision is made.
Does TRT shut down your own testosterone production?
Yes. Exogenous testosterone signals the brain that levels are adequate, so LH production drops and the testicles reduce their own output. This is generally reversible early on and less reliably so after years of use. It also suppresses fertility, which is why we discuss it before starting rather than afterwards.
Why is my testosterone low at 35?
Age is rarely the main explanation at 35. What we find with patients is that sleep debt, insulin resistance, visceral fat, chronic stress and untreated thyroid dysfunction account for the majority of low readings in men under 45. All five are measurable and all five are modifiable.
- Leproult R, Van Cauter E. Effect of 1 week of sleep restriction on testosterone levels in young healthy men. JAMA. 2011;305(21):2173–2174. PMID 21632481
- 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.
- Pitteloud N, Hardin M, Dwyer AA, et al. Increasing insulin resistance is associated with a decrease in Leydig cell testosterone secretion in men. J Clin Endocrinol Metab. 2005;90(5):2636–2641.
- Prasad AS, Mantzoros CS, Beck FW, et al. Zinc status and serum testosterone levels of healthy adults. Nutrition. 1996;12(5):344–348.
- Pilz S, Frisch S, Koertke H, et al. Effect of vitamin D supplementation on testosterone levels in men. Hormone and Metabolic Research. 2011;43(3):223–225.
This article is educational and reflects the published literature as of August 2026. It is not a diagnosis or a treatment recommendation for any individual, and any decision about your care belongs in a conversation with a licensed practitioner who has seen your history and your labs.