What is SHBG?
Sex hormone-binding globulin (SHBG) is a protein made by the liver that binds tightly to testosterone and estradiol, controlling how much of each is free and biologically active. Because SHBG determines the free fraction, it is essential for interpreting total testosterone and estradiol results.
Why it matters
SHBG is a sensitive marker of insulin resistance and thyroid and liver status. Low SHBG is a red flag for metabolic syndrome; high SHBG can leave too little free testosterone despite a normal total.
What it measures
The blood concentration of SHBG, used together with total testosterone to calculate free and bioavailable testosterone.
Reference & optimal ranges
Reference ranges vary by lab, assay, age, and sex. The ranges below reflect commonly published adult intervals and are for education only always interpret results with the range printed on your own lab report and a clinician.
High SHBG lowers free testosterone and can cause low-androgen symptoms even when total testosterone is normal.
Common symptoms
- Low libido and fatigue despite normal total testosterone
Potential causes
- Aging
- Hyperthyroidism
- Liver disease
- Estrogen therapy
- Caloric restriction / low body fat
Low SHBG raises the free fraction and is strongly associated with insulin resistance, obesity, and fatty liver.
Common symptoms
- Often none directly; reflects metabolic risk
- May accompany PCOS features in women
Potential causes
- Insulin resistance / type 2 diabetes
- Obesity
- Hypothyroidism
- Androgen or steroid use
- PCOS
How to improve your SHBG
Lifestyle
Improve insulin sensitivity
Weight loss and reduced refined-carbohydrate intake raise low SHBG.
Nutrition
Reduce refined sugar
High insulin suppresses hepatic SHBG production.
Exercise
Regular activity
Improves insulin sensitivity and can normalize SHBG.
Sleep
Adequate sleep
Supports metabolic and hormonal balance.
Frequently asked questions
Scientific references
- SHBG Blood Test Testing.com
- SHBG Blood Test MedlinePlus, U.S. National Library of Medicine
Educational information, not medical advice. This page is for general education and does not replace diagnosis or treatment by a licensed clinician. Do not start, stop, or change any medication, supplement, or treatment based on this content. Reference and optimal ranges vary between laboratories interpret your results with the range on your own report and a qualified professional.