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SHBG Blood Test
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Lab Tests

SHBG Blood Test

An SHBG blood test measures the level of sex hormone binding globulin to help providers understand how much active testosterone is available in your body.

Overview

An SHBG blood test measures the level of a protein called sex hormone binding globulin (SHBG) in your blood. SHBG is made mostly in your liver and binds to sex hormones such as testosterone and estrogen, controlling how much of these hormones are active in your body.

Sex hormones in your blood are either bound to proteins or unbound (free). Free sex hormones work with your tissues to support bone and muscle growth and reproductive health. Hormones bound to SHBG cannot work with your tissues. This test is used to evaluate abnormal testosterone levels when a total testosterone test does not fully explain a patient's symptoms.

Why do I need this test?

You may need this test if you have symptoms of abnormal testosterone levels. In males, symptoms of low testosterone may include:

  • Low sex drive
  • Difficulty getting an erection
  • Fatigue or loss of muscle mass
  • Fertility problems

In females, symptoms of high testosterone may include:

  • Excessive hair growth on the face and body
  • Deepening of the voice
  • Irregular or absent menstrual periods
  • Acne and weight gain
  • Fertility problems

Providers also use this test to help diagnose hormonal disorders like polycystic ovary syndrome (PCOS), monitor hormone treatments, or investigate early puberty in children.

What happens during the test?

A health care professional will take a blood sample from a vein in your arm using a small needle. The process usually takes less than five minutes. There are no special preparations required, though you should inform your provider about all medicines, vitamins, and supplements you take, as some hormone-containing medications can affect SHBG levels.

Understanding Results

Your provider will interpret SHBG levels alongside total testosterone results to estimate free testosterone levels.

Low SHBG levels may indicate that more testosterone is free and available. This can be related to:

  • Hypothyroidism
  • Type 2 diabetes or insulin resistance
  • Obesity
  • Overuse of steroid medicines or anabolic steroids
  • Cushing's syndrome
  • PCOS (in females)

High SHBG levels may indicate that less testosterone is available for your tissues. This can be related to:

  • Liver disease
  • Hyperthyroidism
  • Certain eating disorders
  • Use of estrogen-containing medicines (e.g., birth control pills or hormone replacement therapy)
  • Decreased production of sex hormones in males

Frequently Asked Questions

Fasting is generally not required for an SHBG blood test. However, because SHBG levels can fluctuate slightly throughout the day and in response to stress, providers often recommend having the blood drawn in the morning, ideally between 8:00 AM and 10:00 AM. This timing helps standardize results for comparison with previous tests. You should continue taking your regular medications unless your provider specifically instructs you to stop, as stopping certain drugs could skew the results.
High SHBG levels are often associated with liver disease, hyperthyroidism, or estrogen excess, while low levels may indicate liver dysfunction, insulin resistance, or obesity. If your results are abnormal, your provider will likely correlate them with your total and free testosterone levels to diagnose conditions like hypogonadism or PCOS. Next steps may include additional blood tests to check liver function, thyroid status, or insulin levels, or a review of your medication list to identify potential causes.
SHBG acts as a carrier protein that binds to testosterone, rendering it inactive. If your SHBG levels are high, a significant portion of your total testosterone is bound and unavailable for use, which can result in low free testosterone levels despite a normal total testosterone reading. Conversely, low SHBG levels mean more testosterone is free and active, so a normal total level might still indicate high biological activity. Clinicians use SHBG to calculate free testosterone to get an accurate picture of hormonal status.
Yes, several factors can significantly impact SHBG levels. Estrogen-containing medications, such as oral contraceptives or hormone replacement therapy, typically increase SHBG levels. Conversely, anabolic steroids, insulin, and obesity can lower SHBG. Thyroid function also plays a role, with hypothyroidism often associated with higher SHBG. It is crucial to inform your provider about all current medications, supplements, and recent changes in weight or thyroid treatment to ensure accurate interpretation of your results.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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