Perimenopause vs Amenorrhea: How to Tell the Difference

When Periods Stop or Change

A change in your menstrual cycle, whether periods become irregular, heavier, lighter, or stop altogether, naturally raises questions. Two of the most commonly confused causes are perimenopause and amenorrhea. They can look similar on the surface, but they arise from different hormonal mechanisms and require different responses. Understanding which is more likely in your situation helps you seek the right support.

What Is Perimenopause?

Perimenopause is the transitional phase before menopause, typically beginning in the early to mid-40s, though it can start earlier. It is driven by declining and fluctuating ovarian oestrogen production. Periods become irregular and may be heavier or lighter than usual. Accompanying symptoms often include hot flashes, night sweats, sleep disruption, mood changes, brain fog, vaginal dryness, and joint pain. Perimenopause is a natural developmental stage, not a disorder.

What Is Amenorrhea?

Amenorrhea refers to the absence of menstruation. Primary amenorrhea means periods have never started by age 15 or 16. Secondary amenorrhea means periods have stopped for three months or more in someone who previously had regular cycles, or six months in someone with irregular cycles. Secondary amenorrhea has multiple causes including low body weight, excessive exercise, stress, thyroid disorders, polycystic ovary syndrome, hyperprolactinaemia, and hypothalamic suppression. It is a symptom of an underlying condition rather than a stage of life.

How the Symptoms Overlap and Differ

Both conditions can cause missed periods, fatigue, and mood changes. The key distinguishing features are age, context, and accompanying symptoms. Perimenopause is more likely in women over 40 and typically comes with vasomotor symptoms such as hot flashes and night sweats. Amenorrhea in a younger woman, or in the absence of vasomotor symptoms, points toward another cause. Hypothalamic amenorrhea from undereating or overexercising often comes with low energy, hair loss, and cold intolerance rather than hot flashes.

When to See a Doctor

Key Takeaways

Perimenopause is a natural hormonal transition associated with ageing and typically presents with irregular periods plus a cluster of other symptoms. Amenorrhea is the absence of periods caused by a range of underlying factors unrelated to age-driven ovarian change. If you are unsure which applies to you, a conversation with your GP and a few targeted blood tests will usually clarify the picture. Tracking your symptoms over several months using PeriPlan can provide useful data to share with your doctor.