SHBG
Sex hormone binding globulin — the protein that controls how much of your testosterone and estrogen is actually available for your body to use.
SHBG is a carrier protein made by your liver. It binds to testosterone and estrogen, controlling how much of each is "free" and available. If SHBG is too high, your free testosterone drops even if total testosterone looks normal. If it's too low, it can signal insulin resistance.
What is the SHBG test?
SHBG stands for sex hormone binding globulin. It's a protein your liver makes that grabs onto testosterone and estrogen in your blood and carries them around. While hormones are bound to SHBG, your body can't use them — only the "free" portion is biologically active.
Think of SHBG like a taxi. The hormones sitting in the taxi aren't doing anything yet — only the ones that have gotten out can actually work. Your SHBG level tells you how many taxis are on the road, which directly affects how much usable testosterone and estrogen you have.
This is why you can have a perfectly "normal" total testosterone but still feel symptoms of low testosterone — if your SHBG is high, most of that testosterone is locked up and unavailable.
What your number means
| SHBG (nmol/L) | Men | Women |
|---|---|---|
| < 20 | Low — check insulin resistance, metabolic syndrome | Low — possible PCOS, insulin resistance |
| 20–55 | Optimal range for most men | Normal (low-mid range) |
| 40–120 | High end — free T may be low | Optimal range for most women |
| > 70 (men) / > 150 (women) | Elevated — hormones likely under-available | Elevated — investigate cause |
SHBG is only meaningful alongside total testosterone, free testosterone, and estradiol. A high SHBG with normal total T means your free T is probably low. Always interpret SHBG as part of a hormone panel, not in isolation.
How to improve your SHBG
If SHBG is too high (and free testosterone is low):
- Strength training — resistance exercise is the most reliable way to lower SHBG naturally
- Boron supplementation — 6–10 mg/day has shown modest SHBG reduction in studies
- Adequate protein — low-calorie or very low-protein diets raise SHBG
- Magnesium and zinc — deficiency in either is associated with higher SHBG
- Reduce alcohol — regular drinking raises SHBG significantly
If SHBG is too low (possible metabolic issue):
- Address insulin resistance — low SHBG often points to high insulin; check fasting insulin and HOMA-IR
- Lose visceral fat — excess belly fat drives insulin up and SHBG down
- Reduce refined carbs — blood sugar spikes suppress SHBG production
- Consider berberine or metformin — if insulin resistance is confirmed, these can help normalise both insulin and SHBG
See your full hormone picture in one place
eterni tracks SHBG alongside testosterone, estradiol, and free T — so you understand what's actually happening, not just what the numbers say.
Get early accessFrequently Asked Questions
What is a normal SHBG level?
For men, 20–55 nmol/L is the standard lab range. For women, 40–120 nmol/L. But optimal depends on context — if your total testosterone is normal but free testosterone is low, SHBG may be too high. If SHBG is very low and you have acne or hair loss, it may be letting too much testosterone through.
Does high SHBG mean low testosterone?
Not exactly. High SHBG means more of your testosterone is bound and unavailable. Your total testosterone could look fine on paper, but your free (usable) testosterone may be low. That's why checking SHBG alongside total and free testosterone gives you the complete picture.
How do I lower SHBG naturally?
Strength training, adequate protein, enough sleep, and maintaining a healthy body fat percentage all help. Boron (6–10 mg/day) has shown modest SHBG-lowering effects in studies. Magnesium and zinc may also help. Avoid crash diets and excessive alcohol, both of which raise SHBG.
Should I worry about low SHBG?
Low SHBG (below 20 nmol/L in men) can be a sign of insulin resistance, metabolic syndrome, or type 2 diabetes risk. It also means more free testosterone, which can contribute to acne, oily skin, and hair loss. If your SHBG is consistently low, get your fasting insulin and HbA1c checked.
How SHBG works in your body
SHBG is produced primarily in your liver. Its production is stimulated by estrogen and thyroid hormones, and suppressed by insulin, androgens, and growth hormone. This is why conditions that raise insulin (like metabolic syndrome and PCOS) tend to lower SHBG, while conditions that raise estrogen (like aging in men, or oral contraceptive use in women) tend to raise it.
SHBG binds testosterone with higher affinity than estradiol, so changes in SHBG levels disproportionately affect free testosterone. A 20% increase in SHBG can reduce free testosterone by a similar margin without changing total testosterone at all.
Reference ranges in India
Most Indian labs report ranges similar to Western references (men: 10–70 nmol/L, women: 20–130 nmol/L). However, studies in Indian populations show that metabolic syndrome — which is common in urban India — tends to push SHBG lower than Western averages. If your SHBG is in the low-normal range (15–25 nmol/L as a man), it's worth checking metabolic markers even if the lab flags it as "normal."
Connected supplements & biomarkers
- Boron — the most studied supplement for lowering SHBG; 6–10 mg/day
- Magnesium — deficiency raises SHBG; glycinate form preferred
- Zinc — supports testosterone production and may modestly affect SHBG
- Vitamin D — low vitamin D is correlated with higher SHBG in some studies
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eterni connects your lab results, supplements, and retests — so you can see the trajectory, not just a snapshot.
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