What Is SHBG and Why Does It Matter?
Medically reviewed by Evan Fox, NP
Last updated August 2026
If you have ever been told your testosterone is normal while you still feel like something is off, SHBG is the marker most likely to explain the gap.
SHBG is the reason two men can have identical total testosterone results and completely different symptoms. One feels fine. The other is exhausted, foggy, and losing ground in the gym. The difference is not how much testosterone they have. It is how much of it their bodies can actually use.
Most basic testosterone panels do not include SHBG. That single omission is responsible for a lot of men being told nothing is wrong when something clearly is.
This guide explains what SHBG does, what high and low levels mean, and why interpreting your testosterone without it is guesswork.
Quick Answer
SHBG, sex hormone binding globulin, is a protein made mainly by your liver that binds tightly to testosterone and carries it through your bloodstream. Testosterone bound to SHBG is locked up. Your tissues cannot use it
Roughly 40 to 60 percent of your testosterone is bound to SHBG. Most of the rest is loosely bound to albumin and largely usable. Only about 1 to 3 percent circulates completely free.
Why this matters:
- High SHBG means more testosterone is locked away. Total testosterone can look normal while free testosterone is low, and you get symptoms of deficiency despite a reassuring lab report.
- Low SHBG means more free testosterone relative to your total. It is often a marker of insulin resistance, obesity, or metabolic dysfunction, and it deserves investigation rather than celebration.
Typical adult male reference range is roughly 10 to 57 nmol/L, though ranges vary by lab and rise with age
The practical takeaway: total testosterone alone cannot be interpreted correctly without SHBG. If SHBG was not on your panel, your evaluation is incomplete.
What Is SHBG?
Sex hormone binding globulin is a glycoprotein produced primarily by your liver and released into your bloodstream.
Its job is to bind sex hormones and transport them. It binds several hormones with different strengths:
- Dihydrotestosterone (DHT) most tightly
- Testosterone tightly
- Estradiol less tightly than testosterone
That last detail has a consequence worth noting. Because SHBG holds testosterone more firmly than estradiol, a rise in SHBG reduces free testosterone more than it reduces free estradiol. The ratio between the two shifts. This is part of why high SHBG can produce symptoms that feel like a hormonal imbalance rather than simple deficiency.
Where your testosterone sits at any moment:
The table below reflects typical total testosterone ranges seen across age groups. Lab reference ranges vary by facility and assay method, so always compare your result to the range printed on your own report.
| Fraction | Approximate Share | Available to Tissues? |
|---|---|---|
| Bound to SHBG | 40 to 60% | No, bound tightly |
| Bound to albumin | 40 to 60% | Yes, weakly held |
| Free and unbound | 1 to 3% | Yes, immediately |
Free testosterone is the unbound fraction. Bioavailable testosterone is free plus albumin-bound, which together represent what your body can actually access.
SHBG levels are not fixed. They change with age, body composition, liver function, thyroid status, insulin sensitivity, medications, and alcohol intake
What Does SHBG Do?
SHBG is not simply an inert carrier. It performs several functions.
Transport. Sex hormones do not dissolve well in blood. SHBG makes them transportable.
Regulation of availability. By binding a large share of circulating testosterone, SHBG controls how much is available to act on tissues at any moment. It functions as a buffer and a reservoir.
Protection from clearance. Bound hormone is cleared from the body more slowly, which extends the working life of the testosterone you produce.
Signaling. Research suggests SHBG may have its own receptor-mediated activity rather than purely acting as a carrier, though this is still being characterized.
Why the buffering matters clinically. SHBG smooths out fluctuations. That is helpful under normal conditions. It becomes a problem when SHBG runs high, because the buffer becomes a bottleneck. Your testes may be producing perfectly adequate testosterone that never reaches the tissues that need it.
SHBG and Free Testosterone Explained
This section is the practical core of the page.
The relationship is inverse. Higher SHBG means lower free testosterone at any given total. Lower SHBG means higher free testosterone at that same total.
Consider two men, both with total testosterone at 600 ng/dL:
Man A has SHBG at 25 nmol/L, in the lower-middle of the range. A healthy proportion of his testosterone is free and bioavailable. He feels good. Energy, libido, and training response are all where he expects.
Man B has SHBG at 75 nmol/L, well above range. Far more of his testosterone is bound and unavailable. His free testosterone sits below optimal. He is fatigued, his libido has dropped, and he cannot make progress in the gym.
Same total testosterone. Same reassuring lab flag. Completely different clinical situations.
This is why a man can have symptoms with a normal testosterone result. Total testosterone measures inventory. Free testosterone measures what is in circulation and usable. SHBG is what determines the ratio between them.
How free testosterone is determined. It can be measured directly by equilibrium dialysis, considered the reference standard but less commonly available, or calculated from total testosterone, SHBG, and albumin using validated formulas. Calculated free testosterone is widely used and generally reliable. Some direct immunoassay methods for free testosterone are considered less accurate and are best interpreted cautiously.
The implication for treatment. A man with high SHBG may need a different approach than a man with the same total testosterone and normal SHBG. Simply pushing total testosterone higher can work, but addressing the drivers of elevated SHBG is often part of the answer.
Causes of High SHBG
- High SHBG reduces the testosterone your body can use. Common drivers:
- Aging. SHBG rises steadily with age. This compounds the age-related decline in total testosterone. An older man frequently has both less testosterone and a smaller usable fraction of it, which is why free testosterone often declines faster than total.
- Hyperthyroidism. Elevated thyroid hormone strongly increases SHBG production. This is one reason a thyroid panel belongs in a hormone workup.
- Liver disease. SHBG is made in the liver. Cirrhosis and chronic liver conditions frequently raise it.
- Being underweight or in significant caloric restriction. Aggressive dieting and low body fat can push SHBG up.
- Anorexia and eating disorders. Associated with markedly elevated SHBG.
- Estrogen exposure. Estrogens stimulate SHBG production.
- Certain medications. Some anticonvulsants and other drugs raise SHBG.
- HIV and some chronic infections.
- Genetics. Some men simply run high without any identifiable cause.
- Symptoms of high SHBG are essentially the symptoms of low free testosterone: fatigue, low libido, erectile difficulty, brain fog, low motivation, and poor training response, all occurring while total testosterone looks acceptable. That mismatch between how you feel and what your report says is the signature finding.
Causes of Low SHBG
- Low SHBG raises your free testosterone fraction, which sounds beneficial. In practice it is more often a warning sign than good news, because the conditions that lower it are ones you want to know about.
- Insulin resistance and type 2 diabetes. High insulin suppresses SHBG production in the liver. Low SHBG is a recognized marker of insulin resistance and is associated with elevated risk of developing type 2 diabetes.
- Obesity. Particularly visceral fat. Strongly associated with low SHBG.
- Metabolic syndrome. The cluster of abdominal obesity, high blood pressure, elevated blood sugar, and abnormal lipids.
- Non-alcoholic fatty liver disease. Directly affects the tissue that makes SHBG.
- Hypothyroidism. Low thyroid hormone reduces SHBG, the mirror image of hyperthyroidism.
- Anabolic steroid or high-dose testosterone use. Exogenous androgens suppress SHBG substantially.
- Corticosteroids.
- Growth hormone excess.
Why low SHBG deserves attention. It is one of the more useful incidental findings on a hormone panel. A low result should prompt a look at fasting glucose, HbA1c, insulin, lipids, and liver markers. Men frequently discover early metabolic dysfunction this way, years before it would otherwise be caught. Treating that is often more valuable than anything done with testosterone directly.
The complication it creates. With low SHBG, total testosterone can read low while free testosterone is adequate. This can lead to a man being treated for low testosterone when his usable fraction was fine, or to under-treatment when the interpretation goes the other way. Either error is avoided by measuring SHBG.
Why Total Testosterone Alone Can Be Misleading
High SHBG masks deficiency. Total testosterone reads normal. Free testosterone is low. The man has symptoms and is told he is fine. He leaves without an answer and often without a follow-up.
Low SHBG can overstate deficiency. Total testosterone reads low. Free testosterone is adequate. He may be started on therapy he did not need, when the real finding was metabolic and should have been addressed differently.
Both errors come from the same omission. Total testosterone is a measure of supply. It says nothing about access.
Where this shows up most often:
- Older men, where rising SHBG means free testosterone falls faster than total
- Men with obesity or insulin resistance, where SHBG is suppressed
- Men with thyroid dysfunction in either direction
- Men with liver conditions
- Lean, heavily training men, who sometimes run high SHBG
- Men whose symptoms clearly do not match their reported results
What a complete evaluation includes. Total testosterone, free testosterone, SHBG, albumin, LH, FSH, prolactin, thyroid panel, CBC, comprehensive metabolic panel, and PSA where age-appropriate.
At Men’s Health Co., our Elite Hormone Panel was built to avoid exactly this failure. It is designed to show what your level is, why it is where it is, and what can actually be corrected, rather than producing a single number and a shrug.
How SHBG Is Tested
The test itself is a simple blood draw, usually run as part of a hormone panel rather than in isolation.
Test conditions:
- Morning draw, ideally between 7:00 and 10:00 AM, to align with testosterone testing
- Fasted, which improves the accuracy of the metabolic markers drawn alongside
- Not during acute illness, which can shift results
- Consistent lab, so results are comparable over time
Typical reference range for adult men is roughly 10 to 57 nmol/L. Ranges vary by lab and assay, and the upper end tends to rise with age. Always compare against the range on your own report.
What to run alongside it. SHBG in isolation tells you little. Interpreted with total testosterone, albumin, and calculated free testosterone, it becomes one of the most informative numbers on your panel. Thyroid and metabolic markers help identify why it sits where it does.
Frequency. Baseline before treatment, then periodically. SHBG changes with weight, thyroid status, and treatment, so it is worth retesting rather than assuming your first result is permanent.
Interpreting SHBG Results Alongside Testosterone
A practical framework. This is a guide to thinking, not a substitute for a provider reading your full panel.
| Total Testosterone | SHBG | Free Testosterone | Likely Picture |
|---|---|---|---|
| Normal | High | Low | Functional deficiency despite normal totals. Symptoms common. Investigate thyroid, liver, and age-related rise. |
| Normal | Normal | Normal | No evidence of hormonal deficiency. Look elsewhere for symptoms. |
| Low | Low | Borderline or normal | Often metabolic. Check insulin resistance, weight, and liver. Treat the metabolic driver. |
| Low | High | Low | Clear deficiency compounded by poor availability. |
| Low | Normal | Low | Straightforward deficiency. Confirm with repeat morning labs and check LH and FSH for cause. |
| High | Low | High | Investigate exogenous androgen use or other cause. |
Frequently Asked Questions
What is a normal SHBG level for men?
Roughly 10 to 57 nmol/L in most labs, with the range varying by facility and tending to rise with age. Interpret your result against the range on your own report and alongside your testosterone values.
Can I have low free testosterone with normal total testosterone?
Yes, and high SHBG is the most common reason. More of your testosterone is bound and unavailable, so you experience symptoms of deficiency despite a normal-looking total.
How do I lower my SHBG?
Address the driver rather than the number. Correcting hyperthyroidism, improving liver health, reducing alcohol, and avoiding severe caloric restriction can all help. Some men run high genetically. Any approach should be provider-directed after the underlying cause is identified.
Is low SHBG a bad thing?
Often it signals insulin resistance, obesity, metabolic syndrome, or fatty liver. The low SHBG itself is not the problem. What it reveals usually is, and it is worth investigating.
Does SHBG increase with age?
Yes, typically rising steadily through adult life. Combined with declining total testosterone, this means free testosterone frequently falls faster than total does.
Should SHBG be on every testosterone panel?
For a meaningful evaluation, yes. Without it, free testosterone cannot be calculated and total testosterone cannot be properly interpreted.
Does TRT affect SHBG?
Testosterone therapy generally lowers SHBG, particularly at higher doses. This raises the free fraction and is one reason free testosterone should be monitored on treatment rather than total alone.
What symptoms does high SHBG cause?
The symptoms of low free testosterone: fatigue, low libido, erectile difficulty, brain fog, low motivation, and poor response to training, all occurring alongside a normal total testosterone result.
Can diet affect SHBG?
Yes. Severe caloric restriction and very low body fat tend to raise it. Excess weight and insulin resistance tend to lower it. Alcohol intake and liver health both influence it.
How is free testosterone calculated?
Most commonly from total testosterone, SHBG, and albumin using a validated equation. Direct measurement by equilibrium dialysis is the reference standard but is less widely available.
Does thyroid affect SHBG?
Substantially. Hyperthyroidism raises SHBG and hypothyroidism lowers it. This is one reason a thyroid panel belongs in any thorough hormone evaluation.
Get the Full Picture, Not Just One Number
Most testosterone panels leave SHBG off, then tell men they are fine.
Men’s Health Co. built the Elite Hormone Panel specifically to avoid that. It is designed to show what your testosterone level is, why it is where it is, and what can be corrected. Then you get a full hour with a provider to go through it properly.
Here is how it works:
Book a 15 minute onboarding call
We email you a lab slip for a lab near you
You get your blood drawn
We schedule a full one hour consultation to review your results, discuss risks and benefits, and start treatment if you qualify
Call (775) 540-2100 | Reno, NV | Statewide telehealth