Can Someone with PCOS Have Normal Labs?
Yes, someone with PCOS can have completely normal laboratory results and still have the diagnosis, because PCOS can be diagnosed based on clinical criteria alone without requiring any abnormal lab values. 1, 2
Understanding the Diagnostic Framework
The Rotterdam criteria—the most widely accepted diagnostic standard—requires only two of three features to diagnose PCOS: 3, 4
- Oligo- or anovulation (irregular or absent periods)
- Clinical and/or biochemical hyperandrogenism
- Polycystic ovarian morphology on ultrasound
This means a woman can be diagnosed with PCOS based solely on clinical hyperandrogenism (hirsutism, acne, or alopecia) plus irregular menstrual cycles, without any abnormal laboratory values whatsoever. 1, 2, 5
The Reality of Laboratory Testing in PCOS
Testosterone Testing Has Limited Sensitivity
Even when measuring the most sensitive androgen marker, total testosterone is abnormal in only 70% of women with confirmed PCOS, meaning 30% have normal testosterone levels despite having the condition. 6 When using free testosterone (the most sensitive androgen test), sensitivity reaches 89%, but this still means 11% of PCOS patients have normal values. 1
LH/FSH Ratio Is Frequently Normal
The classic LH/FSH ratio >2 is abnormal in only 35-44% of women with PCOS, making it a poor diagnostic marker that should not be relied upon. 7, 6 This test has such low sensitivity that its use as a biochemical criterion should be abandoned. 6
Other Hormones Are Often Normal
- Androstenedione is elevated in only 53% of PCOS patients 6
- DHEAS shows no significant difference between PCOS and normal women 6
- Prolactin and TSH are measured primarily to exclude other conditions, not to diagnose PCOS 7, 1
Clinical Phenotypes with Normal Labs
The Rotterdam criteria explicitly recognize PCOS phenotypes that may have minimal or no laboratory abnormalities: 3
- Ovulatory PCOS: Women with regular ovulation, clinical hyperandrogenism (visible hirsutism/acne), and polycystic ovaries on ultrasound may have completely normal hormone levels 3
- Non-hyperandrogenic PCOS: Women with anovulation and polycystic ovaries but normal androgen levels represent another recognized phenotype 7, 3
Important Clinical Pitfalls
Do not rule out PCOS based on normal laboratory values alone. 1, 2 The diagnosis requires careful integration of:
- Menstrual history: Cycles >35 days suggest chronic anovulation, but even cycles of 32-35 days warrant evaluation 5
- Clinical examination: Hirsutism, acne, androgenic alopecia, and acanthosis nigricans provide crucial diagnostic information 2, 5
- Ultrasound findings: Using modern 8MHz transducers, ≥20 follicles per ovary and/or ovarian volume ≥10mL confirms polycystic ovarian morphology 7, 1
When clinical features and ultrasound findings are present, the absence of biochemical hyperandrogenism does not exclude PCOS. 7, 3 In fact, when irregular menstrual cycles and clinical hyperandrogenism are both present, ultrasound is not even necessary for diagnosis, though it helps identify the complete phenotype. 7
The Bottom Line for Clinical Practice
Approximately 14-30% of women with PCOS will have normal testosterone levels, and even more will have normal LH, FSH, and other hormone measurements. 1, 6 The combination of testosterone, androstenedione, or LH (either alone or in combination) is elevated in only 86% of PCOS patients, meaning 14% have completely normal values for all three markers. 6
Therefore, clinical assessment—including menstrual pattern, physical signs of hyperandrogenism, and ultrasound morphology—remains paramount and can establish the diagnosis even when all laboratory tests return normal. 1, 2, 5