A commonly used blood test for diagnosing premature ovarian insufficiency (POI) may be far less reliable than current medical guidance suggests, according to Newson Research.

POI is menopause in women under 40 and occurs in around one in 30 women and can cause symptoms such as irregular periods, fatigue, low mood, and infertility as well as long term health risks with low hormones.

Lack of consensus

Numerous national and international guidelines recommend measuring levels of follicle-stimulating hormone (FSH) to confirm the diagnosis. However, these guidelines vary on what FSH level actually defines POI, with thresholds ranging from 25 to 40 IU/L (international units per litre). This lack of consensus already creates confusion for clinicians – and findings from Newson Research suggests the problem runs deeper.

In findings presented at the International Society for the Study of Women’s Sexual Health annual meeting in California, researchers reviewed hormone test results from 48 women under 40 who were assessed for suspected POI at the Newson Clinic.

Blood samples were analysed, and the results showed wide variation. FSH levels ranged from just under 2 mIU/mL to more than 93 mIU/mL – a nearly 50-fold difference between individuals. The median level was only 6.4mIU/mL, well below most diagnostic cut-offs.

Single test may misdiagnose

In practical terms, this means many symptomatic women have ‘normal’ or low FSH results despite having POI. Because hormone levels can fluctuate widely from day to day, a single blood test can miss the condition altogether – resulting in women being denied hormone treatments

The authors warn these guidelines are leading to women being wrongly reassured or denied hormone treatments, even when they have clear symptoms, leading to them experiencing both symptoms and health risks. They say relying on one FSH measurement provides limited diagnostic value and that current menopause guidelines should be reconsidered.

Self-testing kit concerns

The findings also raise concerns about the growing popularity of commercial self-testing hormone kits, which typically provide just one FSH result without clinical context.

Researchers say POI should be assessed using a broader clinical picture – including symptoms and menstrual history – rather than depending on a single hormone number.

They hope the research will encourage updates to existing guidance, as well as a more patient-centred approach, ensuring women with POI receive timely diagnosis and appropriate care.

Download a poster summarising Newson Research’s findings below.