Blood Test for Acne: The Hormonal Markers Behind Persistent Breakouts

Persistent acne that does not respond to topical treatments is one of the clearest indicators that something hormonal is driving your breakouts. While teenage acne is typically a transient response to puberty, adult acne — particularly in women over 25 — is overwhelmingly hormonal in nature. A targeted blood test can identify the specific imbalances responsible, turning months of trial and error with skincare products into a focused treatment plan.

How Hormones Drive Acne

Acne forms when sebaceous glands produce excess sebum (oil), which combines with dead skin cells to block pores. Certain hormones — collectively known as androgens — directly stimulate sebum production. When androgen levels are elevated or when the skin is hypersensitive to normal androgen levels, the result is oily skin, clogged pores and inflammatory breakouts concentrated along the jawline, chin, cheeks and upper neck.

Key Biomarkers for Hormonal Acne in Women

Testosterone (Total and Free)

Elevated total testosterone (above 1.7 nmol/L in women) or, more importantly, elevated free testosterone is the most common hormonal driver of female acne. Free testosterone is the portion not bound to SHBG and is therefore biologically active at the skin level. Even mildly elevated testosterone can significantly increase sebum production.

DHEA-S (Dehydroepiandrosterone Sulphate)

DHEA-S is an androgen produced by the adrenal glands. Elevated levels (above 10.8 µmol/L in premenopausal women) can indicate adrenal androgen excess, which is distinct from ovarian-driven androgen elevation. This distinction matters because the treatment approach differs — adrenal-driven acne may respond to stress management and cortisol regulation rather than anti-androgen medication.

SHBG (Sex Hormone-Binding Globulin)

Low SHBG means more free testosterone available to stimulate the skin. SHBG below 30 nmol/L in women is commonly associated with acne, hirsutism and other signs of androgen excess. Factors that lower SHBG include insulin resistance, obesity, hypothyroidism and polycystic ovary syndrome (PCOS).

The PCOS Connection

Polycystic ovary syndrome is the most common endocrine disorder in women of reproductive age, affecting 8–13% in the UK. Acne is one of its hallmark features, alongside irregular periods, hirsutism (excess hair growth), hair thinning and difficulty managing weight. PCOS is characterised by elevated androgens, often with a raised LH:FSH ratio (above 2:1) and multiple small follicles visible on ultrasound. A blood test covering testosterone, SHBG, LH, FSH and DHEA-S provides the foundation for a PCOS assessment.

HbA1c and Insulin Resistance

Insulin resistance is increasingly recognised as a central driver of hormonal acne, even in women without PCOS. When insulin levels are chronically elevated, the body produces more androgens and less SHBG — a double hit that amplifies acne. HbA1c above 42 mmol/mol suggests impaired glucose regulation. High-glycaemic diets (white bread, sugary drinks, processed carbohydrates) exacerbate insulin spikes and have been directly linked to acne severity in clinical studies.

Key Biomarkers for Acne in Men

Testosterone and DHT

In men, acne is more commonly linked to dihydrotestosterone (DHT), a potent metabolite of testosterone that is five to ten times more active at androgen receptors in the skin. Men using anabolic steroids or testosterone replacement therapy frequently develop severe acne as a direct consequence of elevated DHT. Total testosterone above 29 nmol/L or clinical signs of high DHT (acne, oily skin, accelerated hair loss) warrant investigation.

Vitamin D and Zinc

Vitamin D deficiency (below 50 nmol/L) has been associated with increased acne severity in several studies. Vitamin D has anti-inflammatory and antimicrobial properties that help regulate the skin's immune response. Similarly, zinc plays a role in wound healing and inflammation control — low zinc levels have been consistently linked to more severe acne presentations.

Patterns That Guide Treatment

• High testosterone + low SHBG + irregular periods: Investigate PCOS; consider anti-androgen therapy
• High DHEA-S + normal testosterone: Adrenal-driven androgen excess; focus on cortisol and stress
• Elevated HbA1c + acne: Insulin resistance contributing; dietary intervention can significantly improve skin
• Low vitamin D + inflammatory acne: Supplementation may reduce inflammation and breakout severity
• Normal hormones + persistent acne: Consider skin-level androgen sensitivity; topical treatments may be more appropriate

Recommended Blood Tests

For women, the Female Hormones 7 blood test (£95) covers testosterone, SHBG, oestradiol, FSH, LH, prolactin and thyroid function — the core hormonal panel for investigating acne. If PCOS is a concern, the PCOS Clarity 24 blood test (£143) adds DHEA-S, HbA1c, insulin, a full lipid panel and additional markers relevant to metabolic and reproductive health. For men, the Male Hormones Clarity 14 blood test (£110) includes testosterone, SHBG, oestradiol, prolactin and thyroid markers.

The Bottom Line

If your acne has resisted topical treatments, prescription retinoids and dietary changes, the answer may be circulating in your bloodstream. Hormonal acne requires a hormonal solution, and identifying the specific imbalance is the essential first step. A blood test transforms guesswork into a targeted plan.