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Sex Hormone-Binding Globulin (SHBG)

A protein made by your liver that carries testosterone and estradiol in your blood. It helps set how much of each hormone is free to act.

AI-verified against cited sources. Awaiting expert reviewAlso called SHBG, TeBGLOINC 13967-5

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The usual range for SHBG depends on sex. Choose female or male above to see where you stand.

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What it is

Sex hormone-binding globulin (SHBG) is a protein made mostly by the liver. It grabs onto testosterone and estradiol in your blood and carries them around. Hormone attached to SHBG is held in reserve, so SHBG helps decide how much is free for your cells to use. Levels are usually higher in women than in men. They are high in young children and fall through puberty. They are also changed by estrogen, thyroid hormone, body weight and liver health.

Why it matters

SHBG helps explain a testosterone result. Two people with the same total testosterone can have different amounts of free, usable testosterone if their SHBG differs. Clinicians often look at SHBG when total testosterone is close to the edge of the range, or when something that changes SHBG is going on, such as obesity, thyroid disease or liver disease. In studies, low SHBG is linked to insulin resistance and a higher chance of developing type 2 diabetes. That pattern is seen across groups of people. It does not predict what will happen to you.

If it’s low

A lower SHBG means less hormone is held in reserve, so a larger share of testosterone is free. Total testosterone can read low even when free testosterone is fine. Low SHBG is common in people with extra body weight or insulin resistance. It can also be linked to an underactive thyroid, androgen medicines and polycystic ovary syndrome (PCOS). Your clinician can put it in context.

Common causes

  • Extra body weight, including fat stored in the liver
  • Insulin resistance, prediabetes, type 2 diabetes and metabolic syndrome
  • An underactive thyroid (hypothyroidism)
  • Testosterone therapy, anabolic steroids and other androgens
  • Polycystic ovary syndrome (PCOS) in women
  • Steroid (glucocorticoid) medicines and Cushing's syndrome
  • Acromegaly, a pituitary condition (uncommon)

What can help

  • Ask your clinician whether weight, blood sugar, thyroid or liver health could explain it
  • Ask whether a calculated or measured free testosterone would give a clearer picture
  • Talk with your clinician about everyday steps that support healthy blood sugar and weight

If it’s high

A higher SHBG means more of your testosterone and estradiol is held tightly. Total testosterone can look normal even when free, usable testosterone is low. High SHBG is common and often has a harmless cause, such as pregnancy, estrogen in birth control or older age. It can also be linked to an overactive thyroid or to liver disease. Your clinician can put it in context.

Common causes

  • Pregnancy, or estrogen in birth control pills or other estrogen medicines
  • Childhood, when SHBG is naturally high before puberty
  • Older age, especially in men
  • An overactive thyroid (hyperthyroidism)
  • Liver disease, including cirrhosis
  • Some anti-seizure medicines
  • Low testosterone production in men (male hypogonadism)

What can help

  • Ask your clinician whether birth control, hormone therapy, a medicine or your thyroid could explain it
  • Ask whether free testosterone or other hormones should be checked alongside it
  • Tell whoever reads your results about any hormones or supplements you use

Usual ranges

What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.

The usual range depends on sex and age. Choose women or men to see the one that applies.

Children and teens 12 ranges

See SHBG by age and sex, with the U.S. survey numbers where they exist.

If this applies to you

SHBG means a little more for some people. Open the one that fits you.

PCOS

The combined pill raises SHBG, a protein that binds testosterone, and lowers the body's own androgen production. That is why the guideline says androgen results are very hard to read while taking it.

Blood tests for PCOS

On testosterone therapy

SHBG is a protein that binds testosterone in the blood. Obesity, diabetes, aging and HIV can shift it, and in those cases the Endocrine Society suggests measuring free testosterone too, since total testosterone alone can mislead.

Blood tests on testosterone therapy

How common is your level?

NHANES describes the US civilian, non-institutionalized population, not a 'healthy' reference group. People with disease, on medication, fasting or not (except fasting-subsample markers), smokers and so on are all included. A percentile says where a value sits among Americans of that sex and age, not whether it is normal.

How SHBG varies with age in the U.S.Shaded: middle 90% and middle 50% of people. Line: the median. nmol/L. Point at any age, or focus the chart and use the arrow keys, to read both sexes in words.

Use the left and right arrow keys to read each age. Shift moves five years.

Reference data derived from CDC/NCHS National Health and Nutrition Examination Survey (NHANES), cycles 2015-2016, 2017-March 2020 (pre-pandemic), August 2021-August 2023. Analysis by bloodtesttracker.com; not endorsed by CDC, NCHS or HHS.

Explore SHBG by age and sex: every percentile as a table, with a download.

What can affect your result

  • Sex and age: levels are higher in women than in men, are high in young children, fall through puberty and tend to be higher in older men
  • Hormones: estrogen and thyroid hormone raise SHBG, and androgens such as testosterone lower it
  • Body weight, insulin resistance, fat in the liver and inflammation tend to lower SHBG
  • Pregnancy raises SHBG markedly
  • Medicines: some anti-seizure drugs raise SHBG, and glucocorticoids lower it
  • Assay method: SHBG tests are not fully standardized, so ranges differ between labs
  • High-dose biotin (vitamin B7) can interfere with immunoassays. Labcorp asks that biotin be stopped at least 72 hours before the draw. Check with your clinician first.
  • Rarely, treatment with mouse (monoclonal) antibodies or very high levels of antibodies to streptavidin or ruthenium can distort an immunoassay result (Labcorp).
  • EDTA plasma and citrate plasma are not accepted (Labcorp).

Any time of day for SHBG itself. If it is drawn with testosterone, follow the early-morning timing that testosterone needs. SHBG has a half-life of about 7 days (Labcorp), so a lasting change in what drives it, such as estrogen or thyroid hormone, can show within a few weeks.

When to talk to a clinician

SHBG on its own rarely needs urgent attention, and no published urgent threshold exists. Talk with a clinician if your result is outside your lab's range and you have symptoms such as changes in sex drive or periods, unwanted hair growth, unusual tiredness or weight change, or if you use hormone therapy.

Questions you could ask

  • Does my SHBG change how you read my testosterone result?
  • Should I repeat this test at the same lab if my medicines or hormone treatment change?
  • Could birth control, hormone therapy, a medicine or my thyroid explain a higher SHBG?
  • Should we check free testosterone, since total testosterone may not tell the full story?
  • Could my weight, blood sugar, thyroid or liver health be related to a lower SHBG?
  • Would a calculated or measured free testosterone give a clearer picture?

Questions people ask

What does SHBG have to do with my testosterone result?

SHBG carries most of the testosterone in your blood. Only the part that is not attached, called free testosterone, is easy for cells to use. When SHBG is high, more testosterone is tied up. When SHBG is low, more is free. Labs use SHBG to calculate free testosterone.

Is a high or low SHBG a problem by itself?

Usually not. SHBG is a clue, not a diagnosis. It rises and falls with estrogen, thyroid hormone, body weight and liver health, so its main use is to help read other hormone results. Your clinician can tell you what your number means for you.

Why is my lab's SHBG range different from another lab's?

SHBG tests are not fully standardized, and ranges also depend on the group of people each lab studied. At Labcorp and ARUP, adult men's ranges run from about 16 to 76 nmol/L and adult women's from about 17 to 125 nmol/L. Compare your result with the range on your own report, and use the same lab when you track changes over time.

Can I convert SHBG between units?

Almost all labs report SHBG in nmol/L. A few report mass units such as ug/mL or mg/L. Those can't be converted reliably, because the conversion depends on the assay. Compare results only when they are in the same unit.

Does birth control change SHBG?

Yes. Estrogen in birth control pills raises SHBG, and so does pregnancy. This is one reason testosterone results are harder to read for someone on the pill. Tell whoever orders your test about any hormones you use.

Show the science and sources

Is a change real?

SHBG naturally varies about 7.4% from test to test in the same healthy person. Between two results from the same lab, a change of roughly 23% or more is unlikely to be day-to-day noise or lab variation (95% reference change value). Source: Sex Hormones and Adrenal Steroids: Biological Variation Estimated Using Direct and Indirect Methods (Roys EA et al.).

For clinicians and researchers

SHBG is a glycoprotein homodimer of about 95 kDa, made mainly by hepatocytes (transcription is driven by HNF4-alpha) with a plasma half-life of about 7 days (Labcorp). Each subunit carries one steroid-binding site. Affinity is highest for DHT, intermediate for testosterone and estradiol, and low for estrone, DHEA, androstenedione and estriol. Albumin binds testosterone much more weakly (about 100-fold lower affinity per Labcorp; Hammond 2016 puts albumin's affinity for steroids 3-4 orders of magnitude below SHBG's) but is far more abundant. Estrogens and thyroid hormone raise hepatic output. Androgens, glucocorticoids, hepatic lipid accumulation, monosaccharides (especially fructose) and inflammatory cytokines lower it, which is why low SHBG is a hallmark of metabolic syndrome (Hammond 2016; EAU 2026 Table 3.3). About 20% of binding sites are occupied in women and about 80% in men (Hammond 2016). Free testosterone can be calculated from total testosterone, SHBG and albumin (Vermeulen 1999), and the free androgen index (total testosterone / SHBG x 100, both in nmol/L) is a cruder surrogate. These calculations assume that every SHBG molecule is detected the same way and binds steroid the same way. Some variants are not recognized by immunoassays or bind differently (for example P156L, which has reduced affinity for testosterone and is present in about 1% of people of European ancestry, Hammond 2016), and in pregnancy estradiol occupies a substantial part of the binding sites, so immunoassay SHBG overestimates binding capacity (Vermeulen 1999). SHBG assays are not harmonized, and intervals differ by method. Labcorp's and ARUP's intervals both come from electrochemiluminescence immunoassays. Mass-unit results (ug/mL, mg/L) are assay-specific and cannot be reliably converted to nmol/L.

LOINC 13967-5 (primary), 2942-1. Specimen: serum.

Sources

  1. Sex Hormone-binding Globulin (test 082016), Labcorp
  2. Testosterone, Free and Total, Includes Sex Hormone-Binding Globulin (Adult Males or Individuals on Testosterone Hormone Therapy) (test 0070109), ARUP Laboratories
  3. Plasma steroid-binding proteins: primary gatekeepers of steroid hormone action, Journal of Endocrinology (2016)
  4. Sex hormone-binding globulin and risk of type 2 diabetes in women and men, New England Journal of Medicine (2009)
  5. A critical evaluation of simple methods for the estimation of free testosterone in serum, Journal of Clinical Endocrinology & Metabolism (1999)
  6. EAU Guidelines on Sexual and Reproductive Health: Male Hypogonadism, European Association of Urology (2026)

AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.

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