What Is SHBG, and Why Read It Alongside Your Testosterone?
Your total testosterone can look normal when the hormone your body can actually use is low, or look low when it is actually adequate. SHBG helps you read the result correctly.
Key points
- SHBG binds testosterone tightly. The active hormone is the free fraction plus the part loosely bound to albumin.
- High SHBG can make total testosterone look normal when little is usable; low SHBG, as in obesity, can make it look falsely low.
- Test SHBG when total testosterone is borderline or a condition may alter SHBG, then calculate free testosterone.
Some patients arrive puzzled by their blood results: "My testosterone is 450, which is normal, so why do I have every symptom of low testosterone?" Another says, "My level is low, but I feel fine." In situations like these, I usually ask for one more value: SHBG. The total number does not tell the whole story of how much hormone your body can actually use.
What is SHBG?
SHBG (sex hormone-binding globulin) is a protein made by the liver. Its job is to bind sex hormones in the blood: testosterone, DHT and oestradiol.
In men, testosterone in the blood is divided roughly into three parts:
| Fraction | Approximate share | Usable by the body? |
|---|---|---|
| Tightly bound to SHBG | 40–60% | Hardly at all |
| Loosely bound to albumin | 40–50% | Yes, it is released easily |
| Free testosterone | 1–3% | Yes |
The albumin-bound part plus the free part is called bioavailable testosterone, the hormone your body can really use.
The total testosterone reported by the laboratory is the sum of all three, so it can be misleading if SHBG is abnormally high or low.
Tightly bound to SHBG
40-60%
- Almost unusable
Loosely bound to albumin
40-50%
- Easily released for use
Free (Free T)
1-3%
- Usable
Albumin-bound + free = bioavailable testosterone, which the body can really use.
What does high or low SHBG mean?
High SHBG
More hormone is held tightly, so less is actually usable. Total testosterone may look normal even though you have symptoms of low testosterone.
Common causes:
- Getting older
- Chronic liver disease or heavy drinking
- An overactive thyroid
- HIV infection (especially in the past or with some drug regimens)
- Major weight loss or malnutrition
- Some anti-epileptic drugs, and oestrogen
Low SHBG
Total testosterone looks low, but free testosterone may still be adequate. Looking only at the total may lead to overdiagnosis.
Common causes:
- Obesity, especially belly fat
- Insulin resistance, type 2 diabetes, metabolic syndrome and fatty liver (read testosterone, diabetes and NCDs)
- An underactive thyroid
- Use of anabolic steroids or glucocorticoids (see steroids and PEDs)
- Nephrotic syndrome
High SHBG
- Total looks normal, but usable portion may be low
- Older age, liver disease, heavy drinking
- Overactive thyroid, major weight loss
Low SHBG
- Total looks low, but Free T may be fine
- Belly fat, insulin resistance, diabetes
- Underactive thyroid, steroid use
Test SHBG when total is borderline, a condition alters SHBG, or symptoms don't match the number.
When should SHBG be tested?
The Endocrine Society, AUA and EAU guidelines recommend using SHBG together with total testosterone to calculate free testosterone in these situations:
- Total testosterone is in the borderline zone, around 200–400 ng/dL (7–14 nmol/L).
- There is a condition that alters SHBG, such as obesity, diabetes, older age, liver disease or thyroid disease.
- Symptoms do not match the total testosterone result.
The summary of the 2026 EAU guideline supports testing SHBG more widely than before, to reduce misdiagnosis.
Free testosterone: measured or calculated?
- Measuring free testosterone directly with the method most general labs use (analogue immunoassay) is often inaccurate, and guidelines advise against it.
- The reference method is equilibrium dialysis, available in specialised laboratories.
- The method most often used in practice is to calculate it from total testosterone, SHBG and albumin using the Vermeulen formula (online calculators exist, such as the ISSAM one).
Thresholds for interpreting free testosterone differ between guidelines. In general, a value below roughly 220–250 pmol/L (64–72 pg/mL) together with symptoms suggests testosterone deficiency, but it must always be read alongside the lab's reference range and your symptoms.
Simple examples of reading results
| Result | Initial interpretation |
|---|---|
| Normal total T, high SHBG, symptoms present | Usable hormone may be low; calculate free T |
| Slightly low total T, low SHBG, belly fat | Free T may be normal; start with weight loss and retest |
| Clearly low total T, normal SHBG, symptoms present | Consistent with testosterone deficiency; look for the cause |
This table is only to help understanding. Diagnosis requires looking at the whole picture, including LH, FSH and symptoms (read blood tests before starting TRT).
SHBG in women and trans people
SHBG matters for everyone. In women, combined contraceptive pills raise SHBG, which may be linked to lower sexual desire in some (read testosterone in women). In gender-affirming hormone therapy, SHBG also changes with the hormones given, so doctors interpret results in each person's context.
When to see a doctor, and how the clinic can help
If you have symptoms of low testosterone but your blood test says normal, or your result is low and you are not sure it can be trusted, bring your results and talk to me. At Dr. Kris Clinic, I test morning total testosterone together with SHBG and albumin when appropriate, calculate free testosterone and explain the results clearly, before deciding on TRT or treating the underlying cause. Consultations are available at the clinic or online, in English.
Medicines and services your doctor may consider
- Testosterone blood test฿800Details & order →
- Pre-hormone / pre-TRT blood panel (7 tests)฿2,990Details & order →
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Frequently asked questions
What is a normal SHBG level?
In most adult men it is about 10–60 nmol/L, but it varies by laboratory and age. Read it against the reference range of the lab that did the test.
Can high SHBG be lowered?
By treating the cause, such as treating an overactive thyroid, cutting down alcohol, managing liver disease or reviewing medicines. There is no standard drug used to lower SHBG directly.
Is testing free testosterone alone enough?
It is not recommended, because direct measurement in general labs is often inaccurate. Test total testosterone with SHBG and albumin, and calculate free testosterone.
Why is total testosterone low in people with obesity?
Partly because SHBG is low due to insulin resistance, and partly because fat genuinely suppresses signals from the brain. Calculating free testosterone helps show how low it really is.
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References
- Rosner W, et al. Position statement: Utility, limitations, and pitfalls in measuring testosterone: an Endocrine Society position statement. J Clin Endocrinol Metab. 2007;92(2):405–413.
- Vermeulen A, Verdonck L, Kaufman JM. A critical evaluation of simple methods for the estimation of free testosterone in serum. J Clin Endocrinol Metab. 1999;84(10):3666–3672.
- Wu FCW, et al. Identification of late-onset hypogonadism in middle-aged and elderly men (EMAS). N Engl J Med. 2010;363:123–135.
- Corona G, et al. EAU Guidelines on Sexual and Reproductive Health: Summary of the 2026 Recommendations for Measurement and Biochemical Confirmation of Hypogonadism. Eur Urol Focus. 2026.
- Bhasin S, et al. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2018;103(5):1715–1744.
This article is for education and does not replace diagnosis or treatment by a doctor. If you have symptoms or concerns, please see a doctor.
