What is the normal range for SHBG?

For adult men, approximately 10-60 nmol/L (18.3-54.1 nmol/L is a commonly cited tighter range). For adult women, approximately 30-90 nmol/L. Ranges are laboratory-dependent and age-indexed, SHBG rises with age, so the upper end shifts up in older men.

Why does SHBG drop on TRT?

Testosterone directly suppresses hepatic SHBG production. Falling SHBG on TRT is an expected physiological adaptation, not a pathology. The practical consequence is that at any given total testosterone, the free fraction is higher than it would be at baseline, which is why Vermeulen free-T calculation is more informative than total T alone once you're on TRT.

What does high SHBG mean?

Elevated SHBG can indicate: hyperthyroidism (SHBG rises with thyroid hormone excess), advanced age, liver disease, estrogen excess (exogenous or endogenous), anti-convulsant medication use, or anorexia. Clinically, high SHBG at normal total T produces low free T and can cause symptoms of hypogonadism despite 'normal' total testosterone.

What does low SHBG mean?

Low SHBG is most commonly seen in: obesity, metabolic syndrome, type 2 diabetes, hypothyroidism, exogenous androgen use (TRT, AAS), glucocorticoid excess, or polycystic ovary syndrome (women). Low SHBG amplifies free testosterone at a given total, which can be clinically favorable if total T is physiologic but can also indicate metabolic dysfunction worth addressing.

When should I test SHBG?

Any time you order total testosterone if free-T calculation is desired. Baseline before starting TRT. Follow-up on TRT to see the drop and adjust Vermeulen free-T interpretation. Any time total T and symptoms disagree (normal T but low-T symptoms, or the reverse).

SHBG (Sex Hormone-Binding Globulin)

The liver-produced glycoprotein that determines how much of your testosterone is free and bioactive vs. tightly bound and functionally unavailable.

Last updated: 2026-04-21 · Maintained by the VitaLog team

TL;DR. SHBG is a liver-produced protein that binds testosterone tightly in circulation. Normal adult-male range is ~10-60 nmol/L. Low SHBG is common on TRT and in metabolic syndrome; high SHBG rises with age and thyroid excess. Whatever your SHBG, the clinical signal for androgen status lives in free testosterone, calculated from total T + SHBG + albumin using the Vermeulen 1999 method.

Definition

Sex Hormone-Binding Globulin (SHBG) is a 90-110 kDa glycoprotein produced primarily by the liver. It binds testosterone, dihydrotestosterone (DHT), and estradiol with high affinity (K ≈ 10⁹ M⁻¹ for testosterone at 37 °C) and transports them through the bloodstream. About 40-60% of circulating testosterone is SHBG-bound and biologically unavailable to tissues. The remaining testosterone is either albumin-bound (loose, "bioavailable") or free (~1-4%).

SHBG is the single most important modulator of androgen availability at any given total testosterone level. Two men with identical total T can have dramatically different symptomatic androgen status if their SHBG differs.

Reference range

Population	Range (nmol/L)	Notes
Adult men (general)	10-60 nmol/L	Rises gradually with age; men ≥70 commonly 40-80
Adult men (TRT typical)	10-30 nmol/L	Expected drop from exogenous testosterone
Adult women (pre-menopausal)	30-90 nmol/L	Estrogen-stimulated production
Adult women (post-menopausal)	20-60 nmol/L	Lower due to falling estradiol
Pregnancy	Markedly elevated (3-10×)	High estrogen drives hepatic production

What high SHBG means

Elevated SHBG can indicate:

Hyperthyroidism: thyroid hormone strongly stimulates SHBG production. Often the first lab clue to subclinical hyperthyroidism.
Advanced age: SHBG rises ~1-2% per year after age 30 in men.
Liver disease: paradoxically, early cirrhosis can raise SHBG before declining in later stages.
Estrogen excess: exogenous (OCP, HRT).
Anti-convulsant use: phenytoin, carbamazepine, and some others increase SHBG.
HIV antiretroviral therapy: protease inhibitors in particular elevate SHBG.
Opioid withdrawal / long-term opioid use: well-documented HPG-axis disruption with secondary SHBG changes.
Anorexia nervosa / severe restrictive dieting.

Clinically, high SHBG with normal total T produces low free T, and the symptoms patients report track free T, not total T. Check thyroid status (TSH, free T4, free T3) when SHBG is unexpectedly high.

What low SHBG means

Suppressed SHBG is most commonly seen with:

Obesity / metabolic syndrome: hyperinsulinemia suppresses hepatic SHBG production. A classic pattern: low-normal total T with low SHBG → free T near normal, but the underlying metabolic state is what needs attention.
Type 2 diabetes: same mechanism as metabolic syndrome.
Exogenous androgens: TRT, anabolic steroid use. Expected, not a problem on its own.
Hypothyroidism: thyroid deficiency suppresses SHBG production.
Glucocorticoid excess: Cushing's syndrome or long-term prednisone use.
Growth-hormone excess: acromegaly.
PCOS (women), hyperandrogenism plus insulin resistance.

Low SHBG on TRT is expected and routine. Low SHBG not on TRT warrants evaluation of insulin resistance (fasting glucose, HbA1c) and thyroid function.

When to test

Any time you order total testosterone: so Vermeulen free-T can be calculated.
Baseline before starting TRT.
Follow-up on TRT at 6 weeks, 3 months, 6 months: expect a drop, use it to recalibrate free-T interpretation.
When symptoms disagree with total T, "my T is 700 but I feel terrible" or "my T is 350 but I feel great" both often resolve in the SHBG + free T direction.
Workup for unexplained hypogonadism along with thyroid panel.

Total Testosterone, paired with SHBG for Vermeulen free-T
Free Testosterone, the bioactive fraction SHBG modulates
TSH, thyroid excess is a classic cause of high SHBG
Vermeulen free-T calculator, compute free T from SHBG + total T + albumin
TRT bloodwork guide, SHBG in the full panel context

FAQ

What is the normal range for SHBG?: For adult men, approximately 10-60 nmol/L (18.3-54.1 nmol/L is a commonly cited tighter range). For adult women, approximately 30-90 nmol/L. Ranges are laboratory-dependent and age-indexed, SHBG rises with age, so the upper end shifts up in older men.
Why does SHBG drop on TRT?: Testosterone directly suppresses hepatic SHBG production. Falling SHBG on TRT is an expected physiological adaptation, not a pathology. The practical consequence is that at any given total testosterone, the free fraction is higher than it would be at baseline, which is why Vermeulen free-T calculation is more informative than total T alone once you're on TRT.
What does high SHBG mean?: Elevated SHBG can indicate: hyperthyroidism (SHBG rises with thyroid hormone excess), advanced age, liver disease, estrogen excess (exogenous or endogenous), anti-convulsant medication use, or anorexia. Clinically, high SHBG at normal total T produces low free T and can cause symptoms of hypogonadism despite 'normal' total testosterone.
What does low SHBG mean?: Low SHBG is most commonly seen in: obesity, metabolic syndrome, type 2 diabetes, hypothyroidism, exogenous androgen use (TRT, AAS), glucocorticoid excess, or polycystic ovary syndrome (women). Low SHBG amplifies free testosterone at a given total, which can be clinically favorable if total T is physiologic but can also indicate metabolic dysfunction worth addressing.
When should I test SHBG?: Any time you order total testosterone if free-T calculation is desired. Baseline before starting TRT. Follow-up on TRT to see the drop and adjust Vermeulen free-T interpretation. Any time total T and symptoms disagree (normal T but low-T symptoms, or the reverse).