Low SHBG and Acne: Why Normal Testosterone Isn't the Full Story

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Short answer: SHBG (sex hormone binding globulin) is a protein that holds onto testosterone and keeps it inactive. When SHBG is low, more testosterone is free to act on your oil glands, even if your total testosterone is normal. Studies in women with acne have linked lower SHBG with more severe acne, and in one study of persistent acne, low SHBG was the most common hormonal finding. High SHBG, by contrast, usually means less free testosterone and is not a typical cause of breakouts.

What is SHBG?

SHBG is a protein made mainly by your liver. It carries sex hormones, including testosterone, through your blood and controls how much of them can reach your tissues (Selva et al., 2007). Think of it as a sponge: testosterone that's soaked up by SHBG is on hold. Testosterone that isn't bound is "free" and can act on your skin.

SHBG and free testosterone: why "normal testosterone" can mislead

Most standard hormone tests report total testosterone: everything in your blood, bound and unbound. But researchers have long noted that the free and loosely bound fractions reflect what's happening in your body more accurately than the total (Vermeulen et al., 1999).

Free testosterone can be reliably calculated from total testosterone and SHBG (Vermeulen et al., 1999). That's why SHBG matters: two people with the same total testosterone can have very different amounts of active hormone, depending on their SHBG.

Total T	SHBG	Free T	What it can suggest
Normal	Normal	Normal	Androgen levels are unlikely to be the main driver; look at other factors
Normal or high-normal	Low	High or high-normal	The classic "hidden" pattern: normal testosterone, but more of it is active
High	Low	High	A stronger androgen signal, sometimes seen with PCOS; worth a doctor's review
High	Normal	High	More testosterone is being produced; the source is worth investigating
Normal	High	Low or low-normal	Less active testosterone; seen with hormonal birth control. Acne here likely has another driver

These are patterns, not diagnoses. Your doctor reads them alongside your symptoms, cycle and history.

Does low SHBG cause acne? What the research shows

129 adult women with acne: acne severity and hirsutism (unwanted hair growth) were both linked to lower SHBG. The authors recommended checking SHBG in women with acne (Borgia et al., 2004).
112 women with persistent acne: SHBG was low in both the PCOS and non-PCOS groups, no other hormone was out of range, and total testosterone sat in the high-normal range. Low SHBG was the most common finding (Sardana et al., 2016).
Women with adult-onset acne: a smaller study found SHBG differed from controls only in women who had acne and hirsutism. In women with acne alone, the only difference was higher DHEA-S, an adrenal androgen (Seirafi et al., 2007).
86 women with acne: a 2025 study found raised androgens were common, including in women without obvious androgen signs, but hormone levels did not predict how well treatment worked (Altunel and Tatlıcan, 2025).

The honest takeaway: low SHBG is associated with acne, especially more severe acne and acne with other androgen signs. These are observational studies, mostly in women, so they show a link, not proof that SHBG alone causes breakouts. And it's not the only hormonal pattern: DHEA-S can matter too.

What lowers SHBG?

High insulin. In a small study of women with PCOS, lowering insulin with medication raised SHBG by 32% and cut non-SHBG-bound testosterone by 43%, suggesting insulin directly suppresses SHBG (Nestler et al., 1991).
Sugar processing in the liver. Lab and mouse research found that glucose and fructose reduce SHBG production by liver cells, which may explain why low SHBG tracks with metabolic problems (Selva et al., 2007).
Higher body weight and waist size. In women with PCOS, BMI and waist circumference were strongly linked to lower SHBG (van Bree et al., 2025).
PCOS and fatty liver. Low SHBG is a common feature of PCOS and has been linked to fatty liver disease and insulin resistance (Qu and Donnelly, 2020).

Notice the thread: blood sugar and insulin keep coming up. That's the bridge between diet, metabolism and hormonal acne. More on this in hormonal acne and PCOS.

Can high SHBG cause acne?

Not typically. High SHBG binds more testosterone, so less of it is free. Combined birth control pills are a common reason for high SHBG: a meta-analysis found they raised SHBG substantially and lowered free testosterone by an average of 61% (Zimmerman et al., 2014). Very high SHBG is also seen with an overactive thyroid (Vermeulen et al., 1999).

If you have high SHBG and still have acne, the cause most likely lies elsewhere: adrenal androgens like DHEA-S, stress, inflammation, products or your skin's own sensitivity. If your SHBG was high on the pill and your skin changed after stopping, see acne after stopping birth control.

Low SHBG symptoms in women

SHBG itself doesn't cause symptoms. What you notice comes from having more active testosterone, plus the metabolic picture that often travels with it:

Acne, especially more severe or persistent acne (Borgia et al., 2004; Sardana et al., 2016)
Unwanted hair growth on the face or body (Borgia et al., 2004)
Irregular periods, when low SHBG is part of PCOS (Qu and Donnelly, 2020)
Signs of metabolic strain: in women with PCOS, SHBG under 40 nmol/L was linked to worse metabolic markers (van Bree et al., 2025)

For a fuller checklist, see signs of hormonal acne.

How BreakoutLabs measures SHBG

The BreakoutLabs Acne Root Cause Test measures SHBG, Free Testosterone and Total Testosterone together, so the pattern in the table above is visible, not hidden. It also includes DHEA-S and Albumin, plus Cortisol, hsCRP, Vitamin D, Vitamin B12, Ferritin, Creatinine and HbA1c. The test does not measure insulin; HbA1c, a three-month average of blood sugar, is the blood sugar marker it includes.

You collect a small blood sample at home in the morning with a painless device on the back of your upper arm, it's processed in a CLIA-certified lab, and results are ready 5 business days after the lab receives it. Your Clear Skin Blueprint reads your hormones together, so a normal testosterone with a low SHBG doesn't slip through. See what the test measures, or read why normal bloodwork can miss acne causes.

Frequently asked questions

What is a normal SHBG level for women?

Ranges vary by lab. One acne study used a reference range of 34.3 to 147 nmol/L, and a PCOS study found levels under 40 nmol/L were linked to worse metabolic markers. Your lab report will show the range it uses.

Can you have hormonal acne with normal testosterone?

Yes. If SHBG is low, more of your testosterone is free and active, even when the total looks fine. That's why checking SHBG and free testosterone together is more informative than total testosterone alone.

Can you raise low SHBG?

Research suggests insulin and metabolic health play a big role, and in one small study, lowering insulin raised SHBG. Your doctor can look at what's driving your level and discuss options, which may include lifestyle changes or hormonal treatments.