SHBG (sex hormone binding globulin) is a protein made mainly by the liver that binds tightly to testosterone and estrogen and carries them through the blood, controlling how much of each hormone is free to act on your tissues. It is measured in nanomoles per litre (nmol/L), and for most adults a normal SHBG sits roughly between 10 and 100 nmol/L. Because SHBG decides how much of your sex hormones are actually available, it is almost always read alongside testosterone rather than on its own.
What is SHBG (Sex Hormone Binding Globulin)?
Sex hormone binding globulin is a transport protein produced by the liver. Its job is to bind sex hormones — chiefly testosterone, dihydrotestosterone and estradiol — and hold them in a bound, inactive reserve. Only the small fraction of hormone that is not attached to SHBG (the free fraction, plus a loosely albumin-bound portion) can enter cells and do its work. In this way SHBG acts like a hormone thermostat: when SHBG rises, less hormone is free and active; when SHBG falls, more hormone is unleashed.
A doctor may order an SHBG test when a testosterone or estrogen result does not fit the clinical picture, or when they want to understand how much active hormone a person really has. In men, it helps clarify symptoms of low testosterone when the total testosterone is borderline. In women, it is often checked during the work-up for irregular periods, acne or unwanted hair growth, where a low SHBG can unmask androgen excess. SHBG is also a useful window into metabolic health, because levels drop when the body becomes resistant to insulin. Keeping every reading in one place and watching the trend over time is easy with ExaHealth.
SHBG normal range
Across most Indian and international laboratories, a general adult reference range treats an SHBG of roughly 10 to 100 nmol/L as normal, with values above or below that band graded by how far they stray from it. The table below shows the general tier bands used to interpret a result. These are a starting point only: SHBG is strongly influenced by sex, age, pregnancy and metabolic state, and the unit is always nmol/L.
| SHBG (nmol/L) | How it is read |
|---|---|
| 0-3 | Severely low |
| 4-6 | Moderately low |
| 7-9 | Borderline low |
| 10-100 | Normal |
| 101-130 | Borderline high |
| 131-170 | Moderately high |
| 171-400 | Severely high |
Different laboratories may print slightly different limits depending on the assay they run, so always read your value against the reference range on your own report. A single SHBG number is rarely acted on alone; its real meaning appears when it is combined with your testosterone result.
Normal range by age, sex and condition
SHBG is one of the more context-dependent lab values, and the same number can mean different things depending on who you are. The DB tier bands above are the general reference; the notes below describe how doctors adjust their interpretation qualitatively, without applying different fixed cut-offs. These adjustments follow standard laboratory reference-range practice, not any single fabricated threshold.
| Group or situation | How SHBG behaves | Why it differs |
|---|---|---|
| Adult women vs adult men | Women typically sit higher within the normal band; men lower | Estrogen raises SHBG production by the liver while androgens lower it, so healthy women usually carry more SHBG than men. This is why the same number is read differently by sex. |
| Pregnancy | Rises markedly, often toward the upper end or above | The high estrogen of pregnancy strongly stimulates the liver to make SHBG, so an elevated value in a pregnant woman is expected rather than alarming. |
| Older adults | Tends to drift upward with age, especially in men | SHBG rises gradually in later life, which can lower the free (active) fraction of testosterone even when total testosterone looks steady. |
| Insulin resistance, type 2 diabetes, obesity | Low | High insulin levels suppress the liver's production of SHBG, so a low reading is a well-recognised marker of insulin resistance and metabolic syndrome. |
| PCOS (polycystic ovary syndrome) | Often low | Many women with PCOS have underlying insulin resistance, which lowers SHBG and leaves more free testosterone active — contributing to acne, irregular cycles and excess hair. |
| Thyroid and liver conditions | Overactive thyroid or estrogen-related states raise it; liver disease can shift it either way | Because SHBG is made in the liver and its production responds to thyroid hormone and estrogen, these conditions and some medications (such as oral estrogen) move the level up or down. |
The single most useful thing SHBG does is help estimate free testosterone. A total testosterone measures every molecule in the blood, bound and unbound together, but only the free portion is biologically active. By combining total testosterone with SHBG (and often albumin), laboratories calculate an estimated free or bioavailable testosterone — a far better reflection of how much hormone is truly working. This is why a normal total testosterone with a low SHBG can still mean plenty of active androgen, and why a normal total with a high SHBG can leave someone functionally short of free hormone. For the companion picture, see our guide to testosterone levels and their normal range, and for how these hormones shift across a woman's life, our overview of women's hormones through fertility and menopause.
What high SHBG means
A high SHBG — read as borderline above about 100 nmol/L, moderately high above roughly 130, and severely high above about 170 — means more of your sex hormones are locked away in the bound reserve and less is free to act. The commonest reasons are states of high estrogen, such as pregnancy or oral estrogen therapy, and an overactive thyroid (hyperthyroidism). Ageing, low body weight, prolonged fasting and certain liver conditions can also raise SHBG.
The practical consequence of a high SHBG is a reduced free-hormone fraction. In men, this can produce symptoms of low testosterone — low libido, fatigue, low mood — even when the total testosterone reads normal, because the active portion is smaller than the number suggests. This is exactly the situation where measuring SHBG changes the interpretation. Your doctor will read a high SHBG together with your testosterone, thyroid status and symptoms rather than treating the number in isolation.
What low SHBG means
A low SHBG — borderline below about 10 nmol/L, moderately low below roughly 6, and severely low below about 3 — means less hormone is bound and more is free and active. The most important cause is insulin resistance: when insulin levels run high, the liver makes less SHBG, so a low reading frequently accompanies type 2 diabetes, obesity and metabolic syndrome. It is a common and clinically useful early signal of metabolic strain, which is often seen in India alongside central weight gain.
In women, a low SHBG is a recognised feature of PCOS, where it lets more free testosterone circulate and drives symptoms such as acne, oily skin, scalp hair thinning and unwanted facial or body hair. Other causes of low SHBG include an underactive thyroid (hypothyroidism), the use of androgens or anabolic steroids, and some glucocorticoid medicines. Because a low SHBG amplifies the effect of whatever testosterone is present, it is an important number to interpret alongside a total testosterone result.
How to manage or improve your SHBG
SHBG itself is not treated directly; it responds to the underlying state of your metabolism, hormones and liver. Because a low SHBG so often reflects insulin resistance, the same habits that improve metabolic health tend to raise a low SHBG back toward normal:
- Work toward a healthy weight. Excess body fat, especially around the abdomen, drives insulin resistance and pushes SHBG down. Gradual, sustainable weight loss often lifts a low SHBG.
- Improve insulin sensitivity through movement. A mix of regular walking, everyday activity and some strength work helps your body use insulin better, which supports SHBG production by the liver.
- Choose lower-glycaemic, whole foods. An Indian plate built around dals and legumes, plenty of vegetables, whole grains such as millets and brown rice, fruit and nuts, with fewer refined carbohydrates, sugary drinks and fried snacks, helps steady insulin and supports metabolic health.
- Look after your thyroid and liver. Because both organs influence SHBG, getting thyroid problems treated and limiting alcohol supports a healthy level.
- Avoid unprescribed hormones. Over-the-counter "testosterone boosters" and anabolic steroids lower SHBG and distort the whole hormone picture.
When to see a doctor: If you have symptoms of low testosterone, irregular periods, acne or unwanted hair growth, or signs of insulin resistance such as persistent weight gain around the middle, ask your doctor whether an SHBG test alongside testosterone would help. Never start hormone therapy on your own — both the diagnosis and any treatment need medical supervision. You can browse more explainers on the lab tests hub and track your results over time with ExaHealth.
Guidelines and references
- Standard laboratory reference ranges — the general adult SHBG bands (nmol/L) used to grade a result and interpret it against your own report.
- The Endocrine Society — general clinical framework for interpreting sex hormones and estimating free testosterone from total testosterone and SHBG.
Frequently asked questions
What is a normal SHBG level?
For most adults, a normal SHBG (sex hormone binding globulin) is roughly 10 to 100 nmol/L. Different laboratories may print slightly different limits, and the number is interpreted together with your testosterone and by your sex, age and metabolic state.
What does a low SHBG mean?
A low SHBG means more of your sex hormones are free and active. It is most commonly a sign of insulin resistance, obesity or type 2 diabetes, and it is also seen in PCOS and an underactive thyroid.
Why is SHBG measured with testosterone?
Total testosterone counts all the hormone in your blood, but only the fraction not bound to SHBG is active. Combining testosterone with SHBG lets the lab estimate free or bioavailable testosterone, which better reflects how much hormone is actually working.
What causes a high SHBG?
High SHBG is typically caused by high-estrogen states such as pregnancy or oral estrogen, by an overactive thyroid, and by ageing, low body weight or some liver conditions. It leaves less free hormone available to the tissues.
Is low SHBG linked to PCOS?
Yes. Many women with PCOS have underlying insulin resistance, which lowers SHBG and allows more free testosterone to circulate, contributing to acne, irregular periods and excess hair growth.
Can lifestyle changes raise a low SHBG?
Often, yes. Because a low SHBG usually reflects insulin resistance, reaching a healthy weight, exercising regularly and eating lower-glycaemic whole foods can improve insulin sensitivity and lift SHBG back toward normal, alongside any care your doctor advises.