Blood Test for Low Libido in Women: Which Hormones to Check

Low libido affects roughly one in three women in the UK at some point, yet it remains one of the most under-discussed health concerns in GP consultations. Many women assume it is simply a consequence of ageing, stress or relationship dynamics. While psychological factors certainly play a role, reduced sexual desire is frequently driven by measurable hormonal imbalances that a targeted blood test can identify.

Why Hormones Matter More Than You Think

Sexual desire in women is governed by a complex interplay of hormones. When one or more fall outside their optimal range, libido can decline significantly — sometimes gradually, sometimes quite suddenly. The frustrating part is that standard NHS blood panels rarely include the hormones most relevant to sexual function, which means many women never receive a clear explanation for what they are experiencing.

Key Biomarkers to Test

Testosterone

Testosterone is not just a male hormone. Women produce it in the ovaries and adrenal glands, and it plays a central role in sexual desire, arousal and satisfaction. The normal reference range for women is approximately 0.3–1.7 nmol/L, but many women with low libido sit at the bottom of this range or just below it. Post-menopausal women and those on combined oral contraceptives are particularly susceptible to low testosterone levels.

Oestradiol (E2)

Oestradiol is the most potent form of oestrogen and directly influences vaginal lubrication, blood flow to the pelvic region and overall mood. Levels fluctuate across the menstrual cycle, with the follicular phase reference range typically between 46–607 pmol/L. A significant drop — common during perimenopause — can cause vaginal dryness, discomfort during intercourse and a corresponding decline in desire.

Sex Hormone-Binding Globulin (SHBG)

SHBG binds to testosterone and makes it unavailable for use by the body. Elevated SHBG levels effectively reduce the amount of free, active testosterone in circulation. SHBG tends to rise with age, oral contraceptive use and thyroid dysfunction. A normal range is roughly 18–114 nmol/L, but levels above 80 nmol/L in premenopausal women often correlate with low free testosterone and reduced libido.

Prolactin

Prolactin is produced by the pituitary gland and is best known for its role in breastfeeding. Elevated prolactin outside of pregnancy and lactation (above the typical upper limit of 500 mIU/L) can suppress gonadotropin-releasing hormone, which in turn reduces oestrogen and testosterone production. Common causes of elevated prolactin include certain medications (SSRIs, antipsychotics), stress and, rarely, a pituitary adenoma.

Thyroid Function (TSH, Free T4, Free T3)

Both hypothyroidism and hyperthyroidism can significantly dampen libido. Hypothyroidism — affecting around 2% of the UK population, with women five to ten times more likely to be affected — causes fatigue, weight gain and low mood, all of which contribute to reduced sexual desire. TSH above 4.0 mIU/L with low free T4 (below 12 pmol/L) warrants further investigation.

Iron and Ferritin

Iron deficiency is the most common nutritional deficiency worldwide, affecting roughly 25% of women of reproductive age in the UK. When ferritin drops below 30 µg/L, fatigue becomes pronounced, and chronic tiredness is one of the most reliable predictors of low libido. Heavy menstrual bleeding creates a cycle where iron loss worsens fatigue which further reduces desire.

When to Consider Testing

Testing is particularly worthwhile if you are experiencing:

• A noticeable decline in sexual desire that has persisted for several months
• Fatigue or low energy alongside reduced libido
• Perimenopause symptoms (irregular periods, hot flushes, mood changes)
• Use of hormonal contraception, particularly the combined pill
• Difficulty with arousal or satisfaction despite feeling mentally willing

What Happens After Your Results

Once your blood test results are back, you will be able to see exactly where your hormone levels sit relative to optimal ranges. Low testosterone may warrant a discussion with your GP about testosterone replacement (available off-label in the UK as a cream or gel). Thyroid dysfunction can be managed with medication. Iron deficiency responds well to supplementation, though it is important to retest after 8–12 weeks to confirm levels are recovering.

Recommended Blood Tests

The Female Hormones 7 blood test (£95) covers testosterone, oestradiol, SHBG, FSH, LH, prolactin and thyroid function — a targeted panel for investigating low libido. If you want a broader picture that includes additional thyroid markers, cortisol and a full blood count, the Female Hormones Clarity 31 blood test (£115) provides a more comprehensive hormonal assessment.

The Bottom Line

Low libido in women is not something you simply have to accept. In many cases, it has a measurable, treatable hormonal cause. A targeted blood test can cut through months or years of uncertainty and give you a clear starting point for getting your desire back on track.