Sex hormone-binding globulin (SHBG) is a liver-made protein that binds testosterone and estrogen and controls how much of each hormone stays free and biologically active. For most adults, a normal SHBG level falls around 10 to 57 nmol/L in men and 18 to 144 nmol/L in non-pregnant women. Your result helps explain your active hormone levels, even when total testosterone looks normal.
SHBG reference ranges
| Group | Typical range | Units |
|---|---|---|
| Adult men | 10 to 57 | nmol/L |
| Adult women (non-pregnant) | 18 to 144 | nmol/L |
Reference ranges vary by laboratory, assay, age, and pregnancy status, so always read your result against the range printed on your own report and review it with your clinician.
What is SHBG?
SHBG is a transport protein made mostly by your liver. It circulates in your blood and binds tightly to sex hormones, especially testosterone, dihydrotestosterone (DHT), and estradiol. Hormones bound to SHBG are held in reserve and cannot easily enter your cells, so they are not immediately active. Only the fraction that is unbound (free) or loosely attached to albumin can act on tissues. Because SHBG decides how much of your hormone supply is available, it works like a thermostat for hormone activity. Two people can have identical total testosterone yet very different free testosterone if their SHBG differs. That is why measuring SHBG alongside total hormone levels gives a clearer picture of what your body can actually use.
What is a normal SHBG range?
For most adults, a normal SHBG level sits around 10 to 57 nmol/L in men and 18 to 144 nmol/L in non-pregnant women. Women generally run higher than men, partly because estrogen raises SHBG while androgens lower it. These numbers are typical adult ranges, but the exact cutoffs printed on your report depend on the laboratory, the assay used, your age, and, for women, whether you are pregnant or taking hormonal contraception. SHBG also shifts across the lifespan. Levels tend to be higher in childhood, drop through puberty, and then climb again gradually with age, which is one reason older adults often show higher readings. Pregnancy can raise SHBG several-fold because of high estrogen. Because of this variability, a single number matters less than the full context. Your clinician will read SHBG together with total testosterone, estradiol, and your symptoms rather than treating any one value in isolation. A result slightly outside the range is common and does not automatically signal a problem.
What high SHBG means
A high SHBG level means more of your sex hormones are bound and held in reserve, which lowers the free, active fraction. In practice, high SHBG can drop your free testosterone even when total testosterone reads normal, so you may notice symptoms of low androgen activity despite a reassuring total number. Common causes of elevated SHBG include hyperthyroidism (an overactive thyroid), liver disease such as hepatitis or cirrhosis, higher estrogen levels from pregnancy or oral estrogen therapy, and the natural rise that comes with aging. Very low calorie intake, eating disorders, and certain medications including some anticonvulsants can also push SHBG up. In many cases, high SHBG reflects an underlying condition rather than a problem with the protein itself. Possible symptoms tie back to reduced active testosterone and can include low libido, fatigue, low mood, and, in men, reduced muscle mass or erectile changes. Many people have no symptoms at all and only discover a high value on routine testing. Follow up with your clinician if a high SHBG comes with these symptoms, if your free testosterone is low, or if thyroid or liver problems are suspected. Testing thyroid function and liver panels often helps explain the result and guides next steps.
What low SHBG means
A low SHBG level means less of your hormone supply is bound, so a larger free fraction is available to your tissues. On its own that might sound harmless, but low SHBG is often a signal of an underlying metabolic pattern worth understanding. The most common driver is insulin resistance. High insulin levels suppress SHBG production in the liver, so low SHBG frequently travels with obesity, type 2 diabetes, and fatty liver disease. Hypothyroidism (an underactive thyroid) can also lower SHBG, as can high androgen states such as polycystic ovary syndrome (PCOS) in women, and the use of anabolic steroids or some hormone therapies. Because of these links, a low reading is often viewed as one clue toward metabolic syndrome, the cluster of high blood sugar, excess abdominal weight, high blood pressure, and abnormal lipids. In women, low SHBG paired with symptoms like irregular periods, acne, or excess hair growth can point toward PCOS and higher active androgen levels. In men, the picture is usually tied to weight and blood sugar. Follow up with your clinician if your SHBG is low, especially alongside weight gain, high blood sugar, or symptoms of thyroid or hormonal imbalance. Screening for insulin resistance, thyroid function, and related metabolic markers helps clarify the cause.
What affects your SHBG levels
Several factors move SHBG up or down. Insulin is a major one: higher insulin and insulin resistance lower SHBG, while improved insulin sensitivity tends to raise it. Thyroid status matters too, with an overactive thyroid raising SHBG and an underactive thyroid lowering it. Body weight plays a large role, since excess weight and fatty liver usually reduce SHBG. Age generally increases it over time. Estrogen (including pregnancy and oral estrogen) raises SHBG, while androgens lower it. Liver health is central because the liver makes the protein, so liver disease can shift levels in either direction. Certain medications, including anticonvulsants, thyroid hormone, and hormonal therapies, can also change your result.
Which panel is SHBG part of?
SHBG is usually ordered as part of a hormone or reproductive health panel, often alongside total testosterone, estradiol, luteinizing hormone, and follicle-stimulating hormone. Its main practical use is in calculation: SHBG and total testosterone together let your clinician estimate free testosterone and bioavailable testosterone, the fractions your body can actually use. That is why SHBG is rarely interpreted alone and is most useful as part of a complete hormone picture.
How to support healthy SHBG levels
SHBG responds strongly to your metabolic health, so the same habits that support blood sugar and weight tend to keep it in a healthy range. Because insulin resistance lowers SHBG, steps that improve insulin sensitivity often help most: regular physical activity, a balanced diet with enough fiber and adequate protein, and maintaining a healthy body weight. Reducing excess abdominal fat and supporting liver health, including limiting alcohol, can also matter since the liver produces SHBG. Getting enough sleep and managing stress support hormone balance more broadly. If a thyroid condition, medication, or another medical issue is driving your SHBG, treating that underlying cause is usually the key move. None of this is a substitute for medical care. Use these as general lifestyle context, and let your physician interpret your SHBG in light of your full health history and decide whether any treatment is needed.
SHBG FAQ
Is high or low SHBG worse?
Neither is automatically worse; both are clues rather than diagnoses. High SHBG can lower your active testosterone, while low SHBG often signals insulin resistance or metabolic issues. What matters is the underlying cause and how the result fits with your other hormone levels and symptoms.
Can SHBG affect testosterone levels?
Yes. SHBG binds testosterone and controls how much stays free and active. High SHBG can reduce free testosterone even when total testosterone looks normal, while low SHBG raises the free fraction. That is why SHBG is used to calculate free and bioavailable testosterone.
Does low SHBG mean diabetes?
Not by itself, but low SHBG is strongly linked to insulin resistance and is associated with a higher risk of type 2 diabetes and metabolic syndrome. It is a warning sign worth investigating, not a diagnosis. Your clinician may check blood sugar and other metabolic markers.
What causes SHBG to rise?
Common causes include hyperthyroidism, liver disease, higher estrogen from pregnancy or oral estrogen therapy, aging, very low calorie intake, and certain medications. Higher SHBG generally reflects one of these underlying factors rather than a problem with the protein itself.
Can you lower SHBG naturally?
Improving insulin sensitivity often helps, since high insulin lowers SHBG. Regular exercise, a balanced diet, and reaching a healthy weight can shift levels over time. Any changes should be guided by your physician, especially if a thyroid or liver condition is involved.
Do I need to fast before an SHBG test?
SHBG itself usually does not require fasting, but it is often drawn with other hormone or metabolic tests that do. Follow the specific instructions from your clinician or lab, and note any medications or hormone therapy you take.
Related biomarkers
Free testosterone · Bioavailable testosterone · Estradiol · Luteinizing hormone · Follicle-stimulating hormone
References
- MedlinePlus Medical Encyclopedia, SHBG Blood Test.
- StatPearls (NCBI Bookshelf), Physiology, Sex Hormone Binding Globulin.
- Cleveland Clinic, Sex Hormone-Binding Globulin (SHBG) Test.
