Most women hear "menopause" long before they hear "perimenopause," which is backwards, because perimenopause is usually where the actual experience begins. Menopause is a single day, defined retroactively as exactly twelve months after your last period. Perimenopause is everything leading up to that day, the years when your hormones are fluctuating, your cycle is changing, and symptoms may already be showing up even though you haven't reached menopause yet. Perimenopause typically starts in a woman's mid-to-late 40s, though it can begin earlier, sometimes in the late 30s, and the whole phase can last anywhere from a few years to closer to a decade. Most people assume "menopause symptoms" only start once periods stop entirely. In reality, hot flashes, sleep disruption, and mood changes often show up years before that, while periods are still happening, just irregularly. Hormone levels during perimenopause aren't uniformly low, they're erratic, sometimes swinging higher than your baseline before eventually settling lower after menopause. That instability, more than the eventual decline itself, is why perimenopause often feels more chaotic than the postmenopausal years that follow. Common early signs: periods becoming shorter, longer, heavier, lighter, or skipping (sometimes all in the same year), sleep disruption that shows up before hot flashes do, mood changes that feel different from typical PMS, new or worsening anxiety, and brain fog or word-finding trouble. When to talk to a doctor: very heavy bleeding, bleeding between periods, or any bleeding after twelve full months without one should always be evaluated. Beyond that, there's no symptom too minor to bring up.