SHBG (Sex Hormone-Binding Globulin)
| Clinical | Optimal | |
|---|---|---|
| Male | 16 - 55 nmol/L | 20–55 nmol/L |
| Female | 24.6 - 122 nmol/L | 30–90 nmol/L |
What is SHBG (Sex Hormone-Binding Globulin)?
Sex hormone-binding globulin (SHBG) is a protein produced primarily by the liver that acts as a transport vehicle and regulator for sex hormones — mainly testosterone and oestradiol. It binds tightly to these hormones in the bloodstream, rendering them inactive until they are released.
Think of SHBG as a fleet of taxis carrying hormones through your blood. Hormones bound to SHBG cannot enter cells or activate receptors — only the 'free' hormones that have been dropped off can do their job. The higher your SHBG, the more hormones are locked up in taxis and unavailable.
SHBG levels are influenced by age, body composition, thyroid function, liver health, insulin levels, and certain medications. Understanding SHBG is essential for correctly interpreting testosterone and oestrogen results.
Why SHBG (Sex Hormone-Binding Globulin) Matters for Your Health
SHBG is the gatekeeper for sex hormone availability. Without measuring SHBG, you cannot accurately assess how much active testosterone or oestrogen your body actually has access to. A man with high total testosterone but very high SHBG may actually have less bioavailable testosterone than someone with a moderate total level and lower SHBG.
SHBG also has independent health implications. Low SHBG is associated with insulin resistance, metabolic syndrome, type 2 diabetes, and polycystic ovary syndrome in women. High SHBG is associated with osteoporosis, reduced libido, and in men, symptoms of androgen deficiency despite normal total testosterone.
For longevity, SHBG is a useful marker of metabolic health. Very low SHBG often signals insulin resistance and metabolic dysfunction, which are key drivers of accelerated ageing and chronic disease.
SHBG (Sex Hormone-Binding Globulin)& Your Wearable Data
Sex hormone-binding globulin (SHBG) is a carrier protein that binds testosterone and oestradiol, regulating how much of these hormones is biologically active. SHBG levels are influenced by exercise patterns tracked by your wearable: endurance training tends to increase SHBG while resistance training may lower it. Your wearable's training type distribution helps predict SHBG trends.
Body composition, inferable from wearable activity and fitness data, strongly influences SHBG. Higher body fat is associated with lower SHBG (increasing free testosterone but also free oestrogen), while lean body mass from regular exercise supports balanced SHBG levels. Wearable-tracked improvements in fitness and activity typically correlate with healthier SHBG concentrations.
SHBG must be interpreted alongside total and free testosterone for a complete hormonal picture. If your wearable shows good fitness metrics and healthy lifestyle patterns but testosterone seems low, checking SHBG helps determine whether the issue is low production or excessive binding. The interplay between training type, body composition, and SHBG provides a nuanced hormonal picture.
What High SHBG (Sex Hormone-Binding Globulin) May Suggest
High SHBG means more of your sex hormones are bound and unavailable to your cells. In men, this can cause symptoms of low testosterone even when total testosterone appears normal, because free testosterone is reduced.
Common causes of elevated SHBG include ageing, liver disease (the liver produces SHBG, and cirrhosis can increase production), hyperthyroidism, eating disorders and very low body weight, excessive exercise, and certain medications (anti-epileptic drugs, tamoxifen). Oestrogen exposure (including from environmental sources) can also raise SHBG.
In men with high SHBG and symptoms of androgen deficiency, calculating free testosterone is essential. If free testosterone is low due to elevated SHBG, the underlying cause should be addressed rather than simply treating the testosterone level.
What Low SHBG (Sex Hormone-Binding Globulin) May Suggest
Low SHBG means less of your sex hormones are bound, leaving relatively more circulating freely. While this might seem beneficial for testosterone availability, low SHBG is actually a warning sign for metabolic health.
The most common cause is insulin resistance — insulin directly suppresses SHBG production. Obesity, type 2 diabetes, polycystic ovary syndrome (in women), hypothyroidism, and use of anabolic steroids all lower SHBG. Nephrotic syndrome (kidney protein loss) and Cushing's syndrome are less common causes.
Low SHBG in combination with other metabolic markers (elevated insulin, high triglycerides, large waist circumference) strongly suggests metabolic syndrome, which significantly increases cardiovascular and diabetes risk and should be addressed proactively.
How to Optimise Your SHBG (Sex Hormone-Binding Globulin)
Food
For low SHBG (associated with insulin resistance): reduce refined carbohydrates and added sugars, which drive insulin spikes that suppress SHBG. Increase fibre intake from vegetables, legumes, and whole grains. Include healthy fats from olive oil, nuts, and oily fish. Green tea may support SHBG levels. For high SHBG: ensure adequate calorie and fat intake — very low-calorie and very low-fat diets elevate SHBG. Boron-rich foods (raisins, almonds) may help modestly lower SHBG.
Lifestyle
For low SHBG: focus on improving insulin sensitivity through regular exercise (both aerobic and resistance training), weight loss if overweight, and stress management. Avoid excessive alcohol. Improve sleep quality — poor sleep worsens insulin resistance. For high SHBG: review medications that may elevate it, check thyroid function, ensure adequate caloric intake, and consider whether overtraining may be a factor.
Supplements
For low SHBG (insulin resistance): berberine (500 mg twice daily) or inositol may help improve insulin sensitivity, which can normalise SHBG. Magnesium (200–400 mg daily) supports insulin signalling. For high SHBG: boron (6–10 mg daily) has some evidence for modestly lowering SHBG. Vitamin D supplementation if deficient. Address the underlying cause rather than targeting SHBG directly.
When to Speak to Your GP
See your GP if SHBG is significantly outside the reference range, particularly if accompanied by symptoms. Low SHBG with features of metabolic syndrome (central obesity, high blood pressure, abnormal blood lipids) warrants metabolic assessment. High SHBG with symptoms of hormone deficiency warrants investigation of thyroid and liver function. Discuss SHBG in the context of your full hormone profile for the most meaningful interpretation.
References
- NICE. Testosterone deficiency in men — Clinical Knowledge Summaries. cks.nice.org.uk
- BMJ. Hammond GL. Diverse roles for sex hormone-binding globulin in reproduction. Biol Reprod. 2011;85(3):431-441. pubmed.ncbi.nlm.nih.gov
- Endocrine Society. Bhasin S, et al. Testosterone therapy in men with hypogonadism. J Clin Endocrinol Metab. 2018;103(5):1715-1744. pubmed.ncbi.nlm.nih.gov
- NEJM. Ding EL, et al. Sex hormone-binding globulin and risk of type 2 diabetes in women and men. N Engl J Med. 2009;361(12):1152-1163. pubmed.ncbi.nlm.nih.gov
Medical Disclaimer— This content is for general educational and informational purposes only. It does not constitute medical advice, diagnosis, or treatment. Omniwo Ltd is a wellness information service and is not a medical device, clinical laboratory, or regulated healthcare provider under MHRA guidelines. The “optimal ranges” presented on this page are based on published clinical guidelines (WHO, NICE, NHS) and peer-reviewed research; they represent functional wellness targets and may differ from standard laboratory reference ranges. Individual results should always be interpreted by a qualified healthcare professional (such as your GP) who understands your full medical history. Do not start, stop, or change any medication or supplement based solely on this information. If you are experiencing symptoms, seek medical attention promptly.