SHBG

Blood test

Also known as: Sex hormone-binding globulin

There is no single guideline cutoff for SHBG; the result is read against age- and sex-specific ranges with a clinician, mainly to interpret testosterone.

SHBG is a protein made by the liver that carries testosterone and estradiol in the blood. It holds them tightly, so it sets how much of each hormone is free to act. Its main use is to help read a testosterone result correctly.

What it tells you

Most testosterone in the blood is bound, tightly to SHBG or loosely to albumin. Only a small share is free. The part held by SHBG is not available to tissues.
Total testosterone rises and falls with SHBG, even when free testosterone does not change. A high SHBG can hide a low free testosterone behind a normal total.
A low SHBG can make total testosterone look low when free testosterone is fine. That is why guidelines ask for free testosterone when SHBG is altered.
Free testosterone can be calculated from total testosterone, SHBG and albumin. In one study, this matched the reference lab method closely, except in pregnancy.
Low SHBG travels with insulin resistance. In liver cells, fat-making driven by sugar turns SHBG production down.
It changes little through the day, unlike testosterone.

What can throw it off

Estrogen, including the birth control pill, raises it. On the pill, a woman's androgen levels cannot be read reliably.
An overactive thyroid raises it. An underactive thyroid lowers it.
Liver disease and aging raise it. So does severe undereating, as in anorexia nervosa.
Some seizure medicines and HIV disease raise it.
Obesity, diabetes and insulin resistance lower it.
Testosterone and other androgens, steroid medicines and some progestins lower it.
Nephrotic syndrome, a kidney disease that leaks protein, and acromegaly lower it.
Common gene variants can shift it about 10% either way. In pregnancy, the test overstates how much hormone SHBG can carry.

Evidence

Interpreting testosterone

Some human evidenceCEBM Level 2b

In a lab study across a wide range of SHBG, free testosterone calculated from SHBG matched the reference method closely, except in pregnancy. A simpler ratio, the free androgen index, did not. No study has tested whether SHBG-guided care improves outcomes.

Predicting type 2 diabetes

Strong human evidenceCEBM Level 1a

In pooled studies, women with higher SHBG had about 80% lower diabetes risk, and men about half the risk. Genetic studies suggest SHBG plays a causal role. Even so, SHBG is not used to screen for diabetes; blood sugar tests are.

Predicting death in men

Strong human evidenceCEBM Level 1a

Across 9 studies of men, those with the lowest SHBG had about 15% lower risk of death from any cause than those with the highest. SHBG was not linked to new heart disease after adjustment. These are links, and the reason is unknown.

Limits

It is an interpreter, not a diagnosis. Its main use is reading testosterone or estradiol correctly.
There is no better direction. Low SHBG predicts diabetes, while high SHBG in men goes with higher death risk and lower free testosterone.
Many things move it: estrogen, thyroid, liver, weight, insulin resistance, steroids, age and genes. A single value needs that context.
Test methods are not standardized, so results vary between labs. Pregnancy distorts it.
It does not diagnose polycystic ovary syndrome on its own, and it is not a diabetes screening test.
No healthy number exists. The range printed on a lab report is not a goal.

References

Reviewed by Shubham Gupta, MD — Founder & President · November 5, 2026

This page is for education only. It is not medical advice. Decisions about any treatment belong with a physician who knows your history.