Sex Hormone Binding Globulin (SHBG) Biomarker Testing
It measures SHBG, the protein that controls how much testosterone and estradiol is available, with convenient ordering and clear results through Vitals Vault/Quest.
With Vitals Vault, you have access to a comprehensive range of biomarker tests.
Sex hormone–binding globulin (SHBG) is a blood protein that acts like a “carrier” for sex hormones. When SHBG is higher or lower than expected, your total testosterone or estradiol can look normal on paper while the amount your tissues can actually use (often called “free” or “bioavailable”) is meaningfully different.
An SHBG test is most useful when you are trying to make sense of symptoms that do not match a single hormone number. It is also a common companion test when you are monitoring hormone therapy, fertility planning, or conditions that affect metabolism and the liver.
Because SHBG interacts with several systems, your result is best interpreted alongside related labs and your clinical context. Testing can support clinician-directed care, but it cannot diagnose a condition by itself.
Do I need a Sex Hormone Binding Globulin test?
You may benefit from an SHBG test if your symptoms suggest a hormone imbalance but your total testosterone or estradiol result does not explain what you feel. Examples include low libido, erectile changes, fatigue, reduced muscle strength, mood changes, acne, unwanted hair growth, irregular periods, or trouble with fertility.
SHBG is especially helpful when your clinician is trying to estimate free testosterone. A “normal” total testosterone can still be paired with low free testosterone if SHBG is high, and the opposite can happen when SHBG is low.
You may also want SHBG checked if you are starting, adjusting, or monitoring hormone-related medications. This includes testosterone therapy, estrogen-containing contraception, menopausal hormone therapy, or medicines that can influence thyroid or liver function.
If you have known thyroid disease, significant weight changes, suspected polycystic ovary syndrome (PCOS), diabetes/insulin resistance, or liver disease, SHBG can add context to a broader workup. The most actionable next step is usually to pair SHBG with total testosterone, albumin, and (when relevant) estradiol so your clinician can interpret the pattern rather than a single number.
SHBG is measured from a blood sample in a CLIA-certified laboratory; results should be interpreted with your symptoms, medications, and related hormone tests rather than used as a standalone diagnosis.
Lab testing
Order SHBG testing and keep your results organized for easy retesting and trend review.
Schedule online, results typically within about a week
Clear reporting and optional clinician context
HSA/FSA eligible where applicable
Get this test with Vitals Vault
Vitals Vault lets you order SHBG testing without the usual friction, and you can choose whether you want SHBG alone or as part of a more complete hormone picture. Your results are delivered in a clear format so you can review trends over time and bring the data to your clinician.
If your SHBG result raises questions—like why your total testosterone and symptoms do not match—PocketMD can help you generate a focused set of follow-up questions and identify common companion labs to discuss. That way, you spend less time guessing and more time making decisions with context.
When you need to retest, you can reorder easily and keep your results organized in one place, which is particularly helpful when medication changes, weight changes, or thyroid treatment can shift SHBG over weeks to months.
- Order online and test through the Quest network
- Results you can track over time in one dashboard
- PocketMD helps you prepare next-step questions for your clinician
Key benefits of Sex Hormone Binding Globulin testing
- Clarifies how much testosterone or estradiol may be available to your tissues when total levels are misleading.
- Supports calculation or interpretation of free and bioavailable testosterone when paired with total testosterone and albumin.
- Helps explain symptoms of low-androgen or high-androgen states when standard hormone panels look “normal.”
- Adds context for PCOS, insulin resistance, and metabolic patterns that commonly lower SHBG.
- Improves monitoring of hormone therapies and estrogen-containing medications that can raise SHBG and change free hormone levels.
- Flags common confounders such as thyroid status, liver function, and nutritional status that influence hormone binding.
- Makes retesting and trend review more meaningful by separating hormone production from hormone binding effects.
What is Sex Hormone Binding Globulin (SHBG)?
SHBG is a protein made primarily by your liver that binds tightly to sex hormones in the bloodstream, especially testosterone and estradiol (a main form of estrogen). When a hormone is bound to SHBG, it is generally less available to enter tissues. In practical terms, SHBG helps determine the balance between “total” hormone (bound + unbound) and the fraction that is free or loosely bound and more biologically active.
Your SHBG level can change even when your body is producing the same amount of hormone. That is why SHBG is often the missing piece when symptoms and total hormone results do not line up. For example, high SHBG can lower free testosterone even if total testosterone is in range, while low SHBG can increase free testosterone relative to total.
SHBG is influenced by several factors, including thyroid hormones, insulin levels, liver health, inflammation, age, sex, and medications. Because of this, SHBG is rarely interpreted alone; it is most useful as part of a pattern that includes total testosterone, albumin, and sometimes estradiol and gonadotropins (LH/FSH).
SHBG vs. total testosterone vs. free testosterone
Total testosterone measures all testosterone in your blood, including the portion bound to SHBG and albumin. Free testosterone is the small fraction not bound to proteins, and bioavailable testosterone generally includes free testosterone plus the portion loosely bound to albumin. If SHBG shifts up or down, total testosterone may stay similar while free or bioavailable testosterone changes in a way that better matches your symptoms.
Why liver and thyroid health matter
Because SHBG is produced in the liver and regulated by hormones and metabolic signals, conditions affecting liver function or thyroid status can change SHBG. Treating hyperthyroidism can lower an elevated SHBG, and improving insulin resistance or weight-related metabolic stress can raise a low SHBG over time.
What do my Sex Hormone Binding Globulin results mean?
Low SHBG levels
Low SHBG often means a larger share of your sex hormones are unbound, which can increase free testosterone relative to total testosterone. This pattern is commonly seen with insulin resistance, higher body weight, and PCOS, and it can also occur with hypothyroidism or certain medications. Low SHBG can make total testosterone look lower than expected even when free testosterone is adequate, so pairing SHBG with total testosterone and albumin helps avoid misinterpretation. If your symptoms suggest androgen excess (acne, hair growth, scalp hair thinning) or metabolic risk, your clinician may look at glucose/insulin markers and a broader androgen panel.
SHBG in the expected range
An in-range SHBG suggests hormone binding is not a major confounder, but it does not guarantee that free hormone levels are optimal for you. You can still have low or high free testosterone depending on total testosterone and albumin, and symptoms still matter. If you are monitoring therapy, stable SHBG can make trend interpretation easier because changes in total hormone are more likely to reflect changes in production or dosing. When symptoms persist, the next step is usually to review free/bioavailable testosterone estimates and related hormones rather than repeating SHBG alone.
High SHBG levels
High SHBG means more hormone is tightly bound, which can lower free testosterone or free estradiol even when total levels appear normal. This can happen with hyperthyroidism, estrogen exposure (including some contraceptives or hormone therapy), aging, and some liver conditions. If you have symptoms consistent with low free testosterone—such as low libido, fatigue, or reduced strength—high SHBG is a common explanation that changes the interpretation of a “normal” total testosterone. Your clinician may evaluate thyroid labs, liver markers, and medication effects, and may calculate free testosterone to guide next steps.
Factors that influence SHBG
SHBG is sensitive to metabolic and hormonal signals, so context is essential. Thyroid status, estrogen exposure, insulin resistance, liver health, inflammation, and nutritional status can all shift SHBG up or down. Timing and consistency matter too: changes in weight, thyroid treatment, or hormone therapy can take weeks to months to stabilize. For the clearest interpretation, try to test under similar conditions each time and share your medication list (including hormonal contraception and testosterone therapy) with your clinician.
What’s included
Frequently Asked Questions
What does an SHBG test measure?
It measures the amount of sex hormone–binding globulin in your blood. SHBG is a protein that binds testosterone and estradiol and helps determine how much of those hormones is free or bioavailable to your tissues.
Do I need to fast for an SHBG blood test?
Fasting is not usually required for SHBG itself. However, SHBG is often ordered with other labs (like glucose, insulin, or lipids) that may require fasting, so follow the instructions for your full panel.
Why is SHBG important if my total testosterone is normal?
Because SHBG can change how much testosterone is available to your tissues. High SHBG can lower free testosterone even when total testosterone is normal, and low SHBG can raise free testosterone relative to total. This is a common reason symptoms and total testosterone do not match.
What causes low SHBG?
Low SHBG is commonly associated with insulin resistance, higher body weight, and PCOS, and it can also be seen with hypothyroidism or certain medications. Your clinician may interpret low SHBG alongside metabolic markers and an androgen panel to understand the driver.
What causes high SHBG?
High SHBG can occur with hyperthyroidism, estrogen exposure (including some contraceptives or hormone therapy), aging, and some liver-related conditions. When SHBG is high, calculating free testosterone often helps clarify whether symptoms relate to low available hormone.
How often should SHBG be retested?
Retesting depends on why you checked it. If you are adjusting hormone therapy or treating a driver like thyroid disease or insulin resistance, clinicians often recheck in roughly 6–12 weeks to see a stable change, but your situation may call for a different interval.
Can SHBG help with PCOS evaluation?
Yes. Many people with PCOS have lower SHBG, which can increase free testosterone and contribute to symptoms like acne or unwanted hair growth. SHBG is not diagnostic by itself, but it adds useful context when combined with testosterone measures and clinical criteria.