SHBG Blood Test: What It Measures, Preparation, and Results

What is SHBG?

Sex hormone-binding globulin, usually abbreviated SHBG, is a carrier protein made mainly in the liver. Its job is to bind certain sex hormones in the blood, especially testosterone, dihydrotestosterone, and estradiol. When a hormone is tightly bound to SHBG, it is generally not immediately available to act on body tissues. When a hormone is unbound, or only loosely bound to albumin, it is more biologically available.

This is why SHBG is often discussed alongside testosterone testing. A standard total testosterone blood test measures all testosterone in the blood: testosterone bound tightly to SHBG, testosterone weakly bound to albumin, and free testosterone. If SHBG is unusually high or low, the total testosterone number may not match the amount of hormone that is available to tissues. The U.S. National Library of Medicine’s MedlinePlus explains that SHBG testing can help a clinician understand how much testosterone is active in the body when symptoms and total testosterone results do not line up. MedlinePlus: SHBG Blood Test

SHBG is relevant for people of any sex. In adult men, it is often part of an evaluation for symptoms that may be related to low testosterone, such as reduced libido, erectile dysfunction, fatigue, reduced muscle mass, or fertility concerns. In adult women, it may help evaluate symptoms of androgen excess, such as excess facial or body hair, acne, scalp hair thinning, irregular periods, or infertility. In children and adolescents, SHBG may be considered in the context of puberty timing, though pediatric interpretation requires age- and puberty-stage-specific ranges.

What the SHBG blood test measures

The SHBG blood test measures the concentration of sex hormone-binding globulin in serum, typically reported in nmol/L. It does not directly diagnose low testosterone, high testosterone, PCOS, thyroid disease, liver disease, or any other condition. Instead, it provides context for hormone interpretation.

Clinical laboratories may use different immunoassay methods and different reference intervals. For example, Quest Diagnostics lists SHBG test code 30740 with CPT code 84270 and age- and sex-specific reference ranges; Labcorp lists a sex hormone-binding globulin test with CPT code 84270 and notes potential assay interference from high-dose biotin; Mayo Clinic Laboratories lists SHBG as a serum test with adult and pediatric reference intervals and a typical report availability of 1 to 3 days for its performing laboratory. Quest Diagnostics Test Directory | Labcorp SHBG Test | Mayo Clinic Laboratories SHBG

Because ranges vary by lab, age, sex, pregnancy status, medications, and method, the reference interval printed on your own report is the one your clinician will usually use first. Do not compare your result with a random range found online without confirming that the units and patient category match.

Why a clinician may order an SHBG blood test

SHBG testing is most useful when the question is not simply “what is the total testosterone?” but “how much hormone is likely available to tissues?” It is commonly ordered with total testosterone and sometimes albumin so that free or bioavailable testosterone can be estimated.

Possible reasons in men

A clinician may consider SHBG when a man has symptoms suggestive of testosterone deficiency but the total testosterone result is borderline, unexpectedly normal, or inconsistent with symptoms. The Endocrine Society’s clinical practice guideline for testosterone therapy in men recommends assessing free testosterone when total testosterone is near the lower limit of normal or when a condition that alters SHBG is present. The guideline also emphasizes that testosterone deficiency should not be diagnosed from a single number alone; symptoms and consistently low, accurately measured testosterone are part of the evaluation. Endocrine Society guideline in JCEM

Possible reasons in women

In women, SHBG can help evaluate androgen excess. Low SHBG can increase the fraction of testosterone that is free or bioavailable, even if total testosterone is not dramatically elevated. Clinicians may consider SHBG as part of an evaluation for hirsutism, acne, irregular periods, infertility, or suspected PCOS. The Endocrine Society’s hirsutism guideline notes that SHBG is raised by estrogen and suppressed by androgen, insulin-resistant obesity, and hypothyroidism. Endocrine Society hirsutism guideline

Possible reasons in children and adolescents

In children, SHBG levels change across puberty. High SHBG is common before puberty, and levels may decline as sex hormone activity increases. Pediatric SHBG interpretation should be done by a pediatric clinician or pediatric endocrinologist using age, sex, Tanner stage, symptoms, growth pattern, and other hormone tests.

Monitoring hormone-related treatment

SHBG may also be checked during treatment that affects sex hormones, including some testosterone therapy, estrogen-containing therapy, anti-androgen therapy, fertility evaluations, or endocrine treatment plans. The result can help explain changes in calculated free testosterone or bioavailable testosterone. It should not be used by itself to change a dose.

How to prepare for an SHBG blood test

An SHBG test is a routine blood draw, usually from a vein in the arm. The collection itself generally takes only a few minutes. Preparation depends on why the test is being ordered and what other tests are drawn at the same time.

Fasting and timing

For SHBG alone, many labs do not require fasting. However, testosterone has a daily rhythm, especially in younger men, and morning collection is commonly preferred when SHBG is ordered with testosterone. If your clinician ordered glucose, insulin, lipids, or other metabolic tests at the same time, fasting instructions may be different. Follow the instructions on your lab order or patient portal rather than assuming all hormone panels have the same preparation.

Medicines and supplements to mention

Tell the ordering clinician and the lab about medicines and supplements you take. Do not stop prescribed medication unless the prescribing clinician tells you to. The following can matter for SHBG interpretation or assay accuracy:

• Estrogen-containing medicines, including some birth control pills and hormone therapy, may raise SHBG.
• Androgens or anabolic steroids may lower SHBG and alter testosterone interpretation.
• Thyroid disease or thyroid medication changes can affect SHBG through thyroid hormone status.
• Anti-seizure medicines and some other drugs may influence hormone-binding proteins in some people.
• High-dose biotin can interfere with some immunoassays. Labcorp cautions that high-dose biotin supplementation may interfere with its SHBG assay and recommends stopping biotin at least 72 hours before collection when appropriate; Quest notes that routine-dose and mega-dose biotin timing may require different waiting periods. Ask your clinician what is safe for you. Labcorp SHBG Test | Quest Diagnostics Test Directory

What to expect after the draw

Most people can return to normal activities after the blood draw. Mild bruising, soreness, or lightheadedness can occur. Results may be available in a few business days, depending on the lab, ordering route, and whether the sample is sent to a reference laboratory.

Understanding SHBG blood test results

SHBG interpretation is contextual. A value marked “high” or “low” is not a diagnosis. It is a clue that helps explain hormone availability and points toward possible follow-up questions.

If SHBG is high

High SHBG means a larger share of testosterone or estradiol may be bound and less immediately available to tissues. In a man with symptoms of low testosterone, high SHBG can sometimes produce low calculated free testosterone despite a total testosterone value that appears acceptable. In women, higher SHBG can reduce free androgen exposure, although symptoms and the broader hormone pattern matter.

Examples of factors associated with higher SHBG include hyperthyroidism, liver cirrhosis or some liver conditions, pregnancy, oral estrogen use, and certain medications. Quest’s test directory lists increased SHBG concentrations in pregnancy, hyperthyroidism, cirrhosis, oral estrogen administration, and by certain drugs. Quest Diagnostics Test Directory

If SHBG is low

Low SHBG means a smaller share of testosterone is tightly bound. This can increase the free or bioavailable fraction for a given total testosterone result. Low SHBG is often discussed in the setting of insulin resistance, obesity, type 2 diabetes risk, hypothyroidism, Cushing syndrome, acromegaly, androgen exposure, and PCOS evaluation. MedlinePlus lists low SHBG as possibly related to hypothyroidism, type 2 diabetes or insulin resistance, obesity, steroid overuse, Cushing syndrome, and PCOS in females. MedlinePlus: SHBG Blood Test

Low SHBG does not mean a person has PCOS or diabetes. It may lead a clinician to review menstrual history, androgen symptoms, weight changes, thyroid results, A1c or glucose testing, insulin-resistance risk factors, liver health, medication exposure, and the full hormone panel.

Reference ranges are not universal

Reference ranges vary. Quest’s adult ranges, for example, differ by sex and age group, and Mayo Clinic Laboratories publishes its own adult and Tanner-stage pediatric ranges. This is normal: different populations, instruments, antibodies, and calibration approaches can produce different intervals. Always interpret your result using the laboratory report and your clinical circumstances.

Why SHBG is often paired with albumin

Albumin is another blood protein that binds testosterone more loosely than SHBG. Many free testosterone calculations use total testosterone, SHBG, and albumin. Labcorp OnDemand’s comprehensive testosterone panel description explains that albumin and SHBG help calculate free testosterone and provide a clearer picture of hormone availability. Labcorp OnDemand Comprehensive Testosterone Test

Limitations and possible sources of error

• Assay interference: Biotin and certain antibodies can interfere with some immunoassays.
• Timing: SHBG itself is relatively stable, but testosterone varies by time of day, sleep, illness, and other factors.
• Units: SHBG is commonly reported in nmol/L, but always confirm units before comparing.
• Calculation differences: Free testosterone can be directly measured or calculated. Different formulas and methods can yield different values.
• Symptoms are nonspecific: Fatigue, low libido, acne, weight change, hair changes, and menstrual irregularity can have many causes unrelated to SHBG.

Cost and ordering options

The cost of an SHBG blood test depends on whether it is ordered through insurance, a clinician’s office, a hospital system, or a direct-to-consumer lab service. The lowest sticker price is not always the lowest total cost, because some services add physician-order, lab, draw, or mobile-collection fees. If insurance is used, your out-of-pocket cost depends on deductible, copay, network status, medical-necessity rules, and the billing laboratory.

When comparing self-pay options, compare the effective total cost: the test price plus mandatory order or lab fees, required collection fees, and any optional add-ons you actually choose. The examples below are not rankings and prices can change at checkout.

If your main question is testosterone availability, SHBG alone may not be enough. A panel that includes total testosterone, SHBG, and albumin may be more useful than an isolated SHBG result. For women with androgen symptoms, clinicians may consider total testosterone by an appropriate method, free testosterone or calculated measures, DHEA-S, 17-hydroxyprogesterone, prolactin, TSH, pregnancy testing, metabolic testing, or pelvic evaluation depending on the situation.

Practical next steps after you get results

If your SHBG result is outside the reference range, the next step is usually not to “treat SHBG” directly. The more useful approach is to identify why SHBG is high or low and whether it changes the interpretation of testosterone or estrogen activity.

1. Review the full panel. Look at total testosterone, free or bioavailable testosterone, albumin, estradiol when relevant, thyroid tests, liver enzymes, A1c or glucose, and other ordered markers.
2. Confirm timing and preparation. Note the collection time, fasting status, acute illness, sleep disruption, and supplement use, especially biotin.
3. Match labs to symptoms. A lab abnormality without relevant symptoms may be handled differently than an abnormal result with clear clinical signs.
4. Ask whether repeat testing is needed. Testosterone-related diagnoses often require repeat morning testing or confirmation with a more accurate method.
5. Discuss medication effects. Birth control pills, estrogen therapy, testosterone therapy, anabolic steroids, thyroid treatment, and other medicines can change SHBG or change how results should be interpreted.
6. Consider specialist care when appropriate. Endocrinology, reproductive endocrinology, urology, gynecology, or pediatric endocrinology may be appropriate depending on the pattern and symptoms.

Seek prompt medical care if hormone symptoms are accompanied by rapidly progressive virilization, new severe headaches or vision changes, unexplained breast discharge, testicular mass, severe pelvic pain, signs of adrenal excess, or other concerning symptoms. Those situations require individualized medical evaluation rather than self-directed lab interpretation.

FAQs about the SHBG blood test

Is SHBG the same as testosterone?

No. SHBG is a protein that binds testosterone and some other sex hormones. Testosterone is a hormone. SHBG helps determine how much testosterone is bound versus available to tissues.

Why would my doctor order SHBG if my testosterone was normal?

A total testosterone result can be misleading when SHBG is unusually high or low. Measuring SHBG can help calculate or interpret free and bioavailable testosterone, especially when symptoms do not match the total testosterone result.

Do I need to fast for an SHBG blood test?

Often, no fasting is required for SHBG alone. But if testosterone, lipids, glucose, insulin, or other fasting tests are ordered at the same time, you may receive fasting instructions. Morning collection is commonly preferred for testosterone evaluation.

What does high SHBG mean?

High SHBG may mean less free or bioavailable testosterone for a given total testosterone level. It can be associated with hyperthyroidism, pregnancy, oral estrogen use, cirrhosis or some liver conditions, and certain medications. Your clinician will interpret it with your symptoms and other labs.

What does low SHBG mean?

Low SHBG may mean a larger fraction of testosterone is free or bioavailable. It can be associated with obesity, insulin resistance, type 2 diabetes risk, hypothyroidism, androgen exposure, Cushing syndrome, and PCOS evaluation in women. It is not a diagnosis by itself.

Can supplements affect SHBG testing?

Yes. High-dose biotin can interfere with some SHBG immunoassays and may produce inaccurate results. Tell your clinician about biotin, hair-and-nail supplements, bodybuilding supplements, hormones, and over-the-counter products before testing.

Can I lower or raise SHBG naturally?

SHBG can change with thyroid status, liver health, insulin resistance, body weight, hormones, and medications. The safest approach is to address the underlying issue rather than trying to manipulate SHBG directly. Lifestyle changes that improve metabolic health may affect SHBG in some people, but individual results vary.

Is SHBG used to diagnose PCOS?

SHBG can support the evaluation of androgen excess, but it does not diagnose PCOS by itself. PCOS diagnosis is based on clinical history, menstrual or ovulation patterns, signs or lab evidence of hyperandrogenism, ovarian findings when relevant, and exclusion of other conditions.

Is a direct free testosterone test better than calculated free testosterone?

It depends on the method. Some direct free testosterone immunoassays are less reliable than equilibrium dialysis or well-validated calculations using total testosterone, SHBG, and albumin. Your clinician may choose the method based on the clinical question and available laboratory quality.

How long do SHBG results take?

Turnaround varies by lab and ordering route. Some reference laboratories report SHBG in a few business days; Mayo Clinic Laboratories lists report availability of 1 to 3 days for its SHBG serum test, while consumer services may add time for clinical review and portal release.