Your 40s are a decade of gradual, mostly manageable change. For many women this is when perimenopause — the transition toward menopause — quietly begins: periods start to shift, and symptoms like hot flashes, disrupted sleep, and mood changes may appear. At the same time, fertility declines, metabolism and body composition slowly change, and routine screening for blood pressure, cholesterol, and blood sugar becomes more important. None of this happens on a fixed timetable — the ages below are typical, not rules. Below, what to expect organised by body system, and the checks worth putting on your radar.
Your cycle and hormones: perimenopause often begins
Beginning in your 30s and 40s, the estrogen your ovaries make starts to fluctuate. The most common early sign of perimenopause is a change in your menstrual cycle — periods may get longer or shorter, lighter or heavier, or you may skip some entirely, according to the American College of Obstetricians and Gynecologists (ACOG). Perimenopause commonly starts in the mid-to-late 40s and lasts about four years on average, though it can be shorter or considerably longer. The average age of menopause (12 months with no period) is around 51 to 52, per the National Institute on Aging.
Alongside cycle changes, you may notice hot flashes and night sweats, more restless sleep, mood swings, or brain fog. Learn the fuller picture in our guides to perimenopause symptoms, menopause stages, and menopause age. If symptoms are disruptive, both hormonal and non-hormonal options exist — see hormone therapy and talk through what fits you. You can gauge your own pattern with our menopause symptom score.
Worth flagging to a clinician: very heavy bleeding, bleeding between periods, or periods closer than about three weeks apart aren't automatically "just perimenopause" and deserve a check. More on this in menstrual health and gynecologic health.
Fertility in your 40s
Fertility declines with age, and that decline speeds up after the mid-30s. By around age 45, getting pregnant naturally becomes unlikely, ACOG notes in its guidance on aging and fertility — because both the number and quality of remaining eggs fall. That said, pregnancy is still possible until periods have fully stopped, so contraception still matters if you don't want to conceive. If you do hope to conceive in your 40s, an early conversation with an ob-gyn or fertility specialist is reasonable.
Metabolism and body composition
Many women find weight is harder to maintain in this decade. As muscle mass gradually declines and estrogen falls, the body tends to store more fat around the middle. This isn't about willpower — it's physiology. The most effective levers are strength training to protect muscle, adequate protein, and consistent sleep. See weight and metabolism, the best diet for menopause, nutrition, and exercise for menopause for practical starting points.
Heart, blood pressure, and blood sugar
Your 40s are when cardiovascular and metabolic screening ramps up, because risk starts to climb and early signs are usually silent. The U.S. Preventive Services Task Force suggests checking blood pressure at least yearly from age 40. It also recommends screening for prediabetes and type 2 diabetes in adults 35 to 70 who carry extra weight. A cholesterol (lipid) check helps estimate your heart-disease risk. Explore heart health to understand your numbers.
| Screening | Typical in your 40s | Why it matters |
|---|---|---|
| Blood pressure | At least once a year from 40 | Catches silent high blood pressure |
| Cholesterol / lipids | Discussed from about 40 | Estimates heart-disease risk |
| Blood sugar | Ages 35–70 if you carry extra weight | Finds prediabetes early |
| Mammogram | Every 2 years starting at 40 | Breast-cancer screening |
| Cervical screening | Continues (Pap/HPV) | Gynecologic health |
The USPSTF now recommends screening mammograms every two years starting at age 40. Run a personalised list with our health-checks tool, and use lab results to make sense of your numbers.
Bones, joints, and the rest of you
Estrogen helps protect bone, so its decline sets the stage for faster bone loss in the years around menopause — a good reason to build weight-bearing exercise and enough calcium and vitamin D into your 40s now. Most women don't need a bone-density (DEXA) scan until later unless they have risk factors; our guide on DEXA vs at-home bone tests and the bone health hub explain when to start. You may also notice joint aches, hair thinning, sleep trouble, or brain fog. If fatigue, weight change, or mood shifts feel out of proportion, ask about thyroid function too — thyroid conditions are common in this age group and can mimic perimenopause.
What to do now
You don't need to overhaul your life. A few durable habits — strength training, protein, sleep, managing stress, and keeping up with screenings — carry the most weight. Track how you feel with our brain-body check-in, and look ahead with our decade guides for your 50s, your 60s, and your 70s.
Everyone's 40s look a little different, and these ages and timelines are typical patterns rather than firm rules. If your periods, mood, sleep, or energy change in ways that worry you — or you're weighing treatment options — talk to your clinician, who can tailor screening and care to your history.