What it measures
- SHBG (sex hormone binding globulin)
Why SHBG matters
Most testosterone in your blood is bound to SHBG and isn’t available to your body. If your SHBG is high, you can have symptoms of low testosterone even when your total testosterone looks normal. If it’s low, more testosterone is free.
SHBG rises with age, liver conditions and an overactive thyroid, and falls with weight gain, type 2 diabetes and an underactive thyroid. Combined with a testosterone test, it lets your doctor calculate your free testosterone.
Who it’s for
- Symptoms of low testosterone with a normal total testosterone
- Interpreting a borderline testosterone result
- Women with signs of excess androgens
How to prepare
- Drink plenty of water beforehand; it makes the sample quicker and easier to take.
- You don’t need to fast.
- Morning appointments are best if you’re testing alongside testosterone.
- Stop biotin (vitamin B7) supplements 48 hours before, as biotin can affect hormone and thyroid results.
Sex Hormone-Binding Globulin (SHBG) Blood Test: your questions
Should I test SHBG with testosterone?
Yes. SHBG on its own has limited meaning. Together with total testosterone it shows how much testosterone is free and active.
Information on this page is general and doesn’t replace advice from your GP, midwife or consultant. If you feel unwell or are worried about symptoms, contact your GP, call NHS 111 or, in an emergency, 999.