Biomarker
robust evidence
4 min · 3 sources
Published Jun 19, 2026

SHBG (Sex Hormone-Binding Globulin)

Blood protein that carries sex hormones and changes hormone availability.

It can explain why hormone numbers on a lab report do not match your symptoms or what is happening in your body.

Also known as sex hormone binding globulin · sex hormone-binding globulin · SHBG test · SHBG blood test · testosterone binding globulin · TeBG · sex steroid binding globulin

SHBG controls the free fraction of sex hormones in blood, so higher SHBG lowers free testosterone relative to total testosterone ³.
SHBG helps interpret testosterone testing when symptoms and total testosterone results do not match ².
Thyroid disease, liver disease, oral estrogen, pregnancy, obesity, and insulin resistance can shift SHBG ¹.

The number that can make “normal testosterone” misleading

A testosterone lab can look fine on paper while the useful part of the signal is low or high. The reason is that most sex hormone in blood is not floating around alone. Some is attached to carrier proteins. SHBG, short for sex hormone-binding globulin, is one of the main carriers. It is made mostly in the liver, circulates in blood, and binds testosterone and estradiol, a major form of estrogen.

Here is the surprise: SHBG does not measure testosterone or estrogen. It measures how tightly the bloodstream is holding onto part of those hormones. Hormone attached tightly to SHBG is less available to enter tissues. Hormone that is unattached, called free hormone, is more available. Albumin, another blood protein, also carries sex hormones, but it holds them much more loosely than SHBG.

Why the same total testosterone can mean two different things

Total testosterone counts several pools together: testosterone bound tightly to SHBG, testosterone loosely bound to albumin, and free testosterone. If SHBG is high, more testosterone may be tied up, so free testosterone can be lower than expected. If SHBG is low, total testosterone can look low even when free testosterone is less affected. This is why the Endocrine Society recommends checking free testosterone, either by a direct equilibrium dialysis method or by a reliable calculation, when total testosterone is near the lower end or when SHBG is likely to be altered.

Common adult lab ranges are broad and lab-specific. One University of Iowa laboratory lists men: 10 to 80 nmol/L and non-pregnant women: 20 to 130 nmol/L. Mayo Clinic notes that SHBG is useful in evaluating suspected androgen excess in women, infertility, puberty disorders, thyroid hormone excess, and monitoring sex-steroid or anti-androgen therapy. The key point is that SHBG is interpreted with symptoms, sex, age, menstrual or pregnancy status, medications, and related labs.

What pushes SHBG up or down

SHBG often rises with older age in men, thyroid hormone excess, liver cirrhosis, pregnancy, oral contraceptives, and some anti-seizure medicines. It often falls with obesity, hypothyroidism, polycystic ovary syndrome, high androgen states, and insulin resistance. A low SHBG result is not proof of insulin resistance, but it can fit that pattern, especially when waist gain, elevated fasting insulin, high triglycerides, or abnormal glucose results are also present.

One supplement detail matters: high-dose biotin, commonly sold for hair, skin, and nails, can interfere with some SHBG immunoassays. The University of Iowa lab warns that biotin doses above 5 mg within the prior 12 hours may falsely lower SHBG results.

The one decision to make today

If SHBG is flagged and testosterone is part of the question, do not act on total testosterone alone. The strongest next step is to review the result with a clinician using free testosterone calculated from total testosterone, SHBG, and albumin, or measured by a high-quality method when needed. That single move turns SHBG from a confusing extra number into context for the hormone result.

Deep dive

How it works

SHBG binds dihydrotestosterone most strongly, testosterone and estradiol with medium strength, and hormones such as DHEA and androstenedione more weakly. Because it binds and releases hormones reversibly, the SHBG level changes the balance between tightly bound hormone and hormone that can more readily reach tissues.

When you'll see this

The term in the wild

A 42-year-old man has total testosterone of 360 ng/dL, SHBG of 82 nmol/L, and symptoms that do not match the “normal” total testosterone label.

The SHBG value is near or above the upper end of some adult male ranges, such as 10 to 80 nmol/L. More testosterone may be tightly bound, so calculated or accurately measured free testosterone becomes the more useful next result.

This can prevent the common mistake of dismissing symptoms because total testosterone alone was inside the reference range.
A 29-year-old woman being evaluated for acne and irregular cycles has SHBG of 18 nmol/L, with a lab reference range near 20 to 130 nmol/L for non-pregnant women.

Low SHBG can fit with higher androgen effect, polycystic ovary syndrome, obesity, hypothyroidism, or insulin resistance. It does not name the cause by itself.

The result points the visit toward context: cycle pattern, free testosterone or free androgen index, thyroid testing, glucose or insulin markers, and medication history.
Someone takes Nature Made Biotin 5000 mcg daily and gets an unexpectedly low SHBG result.

5000 mcg equals 5 mg. Some SHBG tests can be affected by high-dose biotin taken close to the blood draw, and one lab warns about doses above 5 mg in the prior 12 hours.

Holding biotin before repeat testing, under the lab or clinician’s instructions, may prevent a false interpretation.
A lab report lists SHBG as 115 nmol/L in a person taking an oral combined contraceptive.

Oral estrogen exposure can raise SHBG. In this setting, the SHBG value may reflect the medication effect rather than a new disease signal.

Medication context keeps the result from being overread as a standalone hormone disorder.

Myths vs reality

What people get wrong

Myth

High SHBG means the body has too much testosterone.

Why people believe it Many lab portals display total testosterone and SHBG on the same screen, but they do not automatically show how binding changes free testosterone.

Reality

High SHBG can mean more testosterone is tightly bound in blood. The free amount may be normal, low, or occasionally high depending on total testosterone and albumin.
Myth

Low SHBG is always good because it leaves more testosterone free.

Why people believe it Fitness and testosterone forums often frame SHBG only as something that “steals” testosterone, which ignores why the liver changed SHBG production in the first place.

Reality

Low SHBG can come with obesity, hypothyroidism, polycystic ovary syndrome, high androgen states, or insulin resistance. It can also make total testosterone look lower than expected.
Myth

An SHBG result is exact even if you take hair and nail biotin.

Why people believe it Biotin is sold as a vitamin supplement, so people often do not think of it as something that can distort lab tests. The named issue is biotin interference in immunoassays, the antibody-based tests many labs use.

Reality

Some SHBG tests can read falsely low after high-dose biotin supplements, depending on the lab method.

For anyone using testosterone therapy, oral contraceptives, anti-androgens, thyroid medication, or high-dose biotin, the failure mode to avoid is comparing SHBG results across time without noting medication and supplement changes. A real trend requires the same lab method when possible and a stable testing setup.

Frequently asked

Common questions

Should SHBG be tested fasting and in the morning?

SHBG itself is fairly stable compared with testosterone, but testosterone interpretation is usually best with a morning blood draw in men. If testosterone is being checked at the same time, follow the timing instructions for testosterone.

Can SHBG be changed with supplements?

No supplement reliably “fixes” SHBG in a targeted way. The better approach is to identify the driver, such as thyroid status, oral estrogen use, weight change, liver disease, insulin resistance, or medication effects.

Why did my clinician order albumin with SHBG and testosterone?

Albumin is needed for many calculated free testosterone formulas. SHBG tells how much hormone is tightly bound, while albumin helps estimate the loosely bound portion.

Does SHBG matter for women too?

Yes. SHBG is often useful when evaluating signs of androgen excess, such as acne, unwanted facial hair, irregular cycles, or suspected polycystic ovary syndrome.

Can pregnancy raise SHBG?

Yes. SHBG often rises during pregnancy because estrogen production increases. Pregnancy-specific interpretation should use the clinician’s context rather than standard non-pregnant ranges.

Sources