Perimenopause at 40: What the Signs Mean and When to See Someone

What is perimenopause, and when does it typically begin?

Perimenopause means 'around menopause.' It is the years-long hormonal shift that precedes the final menstrual period — menopause itself is defined as 12 consecutive months without a period. During perimenopause, the ovaries gradually produce less estrogen and progesterone, and hormone levels fluctuate — sometimes dramatically — before settling at a lower baseline.

The average age perimenopause begins is the mid-40s, but a meaningful number of people notice changes in their early 40s or even late 30s. The transition typically lasts four to eight years, though this varies widely 1Ref 1Faubion SS, Crandall CJ, Davis L, El Khoudary SR, Hodis HN, Lobo RA, Maki PM, Manson JE, Pinkerton JV, Santoro NF, Shifren JL, Shufelt CL, Thurston RC, Wolfman W (2022).The 2022 Hormone Therapy Position Statement of The North American Menopause Society.Perimenopause transition timing, hormone therapy as an evidence-based option for vasomotor symptoms in the context of health history. Age-appropriate screening for bone health and metabolic health becomes relevant during this phase 2Ref 2US Preventive Services Task Force (2018).Screening for Osteoporosis to Prevent Fractures: US Preventive Services Task Force Recommendation Statement.Bone health screening becoming relevant during the menopause transition; earlier screening with risk factors.

What are the most common early signs of perimenopause?

Cycle changes are often the first signal: periods may arrive closer together or further apart, become heavier or lighter, or occasionally skip.

Hot flashes — sudden waves of warmth in the face, neck, and chest — are the most recognized symptom; when they happen at night, they are called night sweats and can fragment sleep significantly 1Ref 1Faubion SS, Crandall CJ, Davis L, El Khoudary SR, Hodis HN, Lobo RA, Maki PM, Manson JE, Pinkerton JV, Santoro NF, Shifren JL, Shufelt CL, Thurston RC, Wolfman W (2022).The 2022 Hormone Therapy Position Statement of The North American Menopause Society.Perimenopause transition timing, hormone therapy as an evidence-based option for vasomotor symptoms in the context of health history.

Mood shifts — irritability, low mood, anxiety — are common and are often tied to sleep disruption as much as to hormonal changes directly. People with a history of depression or anxiety are at higher risk for mood episodes during this transition 3Ref 3O'Connor E, Henninger M, Perdue LA, et al. (2023).Screening for Depression and Suicide Risk in Adults: US Preventive Services Task Force Recommendation Statement.Elevated risk of mood episodes during perimenopause, particularly in people with prior history of depression or anxiety.

Difficulty concentrating (brain fog) is frequently reported and is typically temporary.

Vaginal dryness and changes in libido can appear early, though many people notice these later.

Not everyone has all symptoms, and some people have few.

What else could be causing these symptoms?

The symptom picture of perimenopause overlaps significantly with other conditions:

Thyroid dysfunction is common in this age group and can produce near-identical symptoms — fatigue, weight changes, mood effects, and irregular periods. It is one of the first things a clinician will check 4Ref 4Jonklaas J, Bianco AC, Bauer AJ, et al. (2014).Guidelines for the Treatment of Hypothyroidism: Prepared by the American Thyroid Association Task Force on Thyroid Hormone Replacement.Thyroid dysfunction as a common perimenopause mimic in this age group; TSH testing as an early evaluation step.

Stress, sleep deprivation, or significant lifestyle change — major illness, rapid weight change, intensive exercise — can cause irregular cycles and mood symptoms and should not be dismissed even when perimenopause is also present.

Primary ovarian insufficiency (POI) — ovarian function loss before age 40 — is less common but important to evaluate if symptoms appear before 40, particularly with a family history of early menopause.

Polycystic ovary syndrome (PCOS) can persist into midlife; a history of irregular periods since adolescence or signs of androgen excess would support this possibility 5Ref 5American College of Obstetricians and Gynecologists (2018).ACOG Practice Bulletin No. 194: Polycystic Ovary Syndrome.PCOS persisting into midlife; history of irregular periods since adolescence and androgen excess as distinguishing features from perimenopause.

When should I see a clinician, and what can they offer?

You do not need to wait until symptoms are severe. A primary care clinician or gynecologist can review your history, order hormone labs — though results are interpreted cautiously because levels fluctuate — and rule out other causes like thyroid disease.

If symptoms are disrupting sleep, mood, work, or relationships, there are evidence-based options:

• Hormonal approaches — menopausal hormone therapy (MHT) — are well-studied when used appropriately in the context of your personal health history 1Ref 1Faubion SS, Crandall CJ, Davis L, El Khoudary SR, Hodis HN, Lobo RA, Maki PM, Manson JE, Pinkerton JV, Santoro NF, Shifren JL, Shufelt CL, Thurston RC, Wolfman W (2022).The 2022 Hormone Therapy Position Statement of The North American Menopause Society.Perimenopause transition timing, hormone therapy as an evidence-based option for vasomotor symptoms in the context of health history
• Non-hormonal options — certain antidepressants at low doses, and other medications — exist for people who prefer them or for whom hormones are not advised
• Lifestyle adjustments — sleep hygiene, temperature management, regular exercise — have meaningful evidence behind them

If you are younger than 40 with these symptoms, prioritize the appointment — earlier evaluation matters, particularly to assess for POI and its implications for bone and reproductive health.