Perimenopause age: when it starts and how long it lasts

Most women hear about menopause long before they hear the word perimenopause, so the changes of their mid forties can come as a surprise. The timing is more predictable than it feels, and knowing it gives you a few years' head start. What menopause is explains the stages.

When perimenopause starts

The best numbers come from the Massachusetts Women's Health Study, which followed more than 2,500 women in their late forties and early fifties. Perimenopause started at a median age of 47.5 and lasted nearly four years. Menopause, the final period, came at 51.3 on average.¹

The larger and more diverse SWAN study found a median age at the final period of 52.5, and found no difference between racial and ethnic groups once other factors were accounted for.² ACOG gives 51 as the average age of menopause.³

Can it start earlier?

Yes. ACOG notes that estrogen made by the ovaries can start to fluctuate in your 30s and 40s.³ So cycle changes at 40, or even a little before, can be early perimenopause. They can also have other causes, which is why they are worth mentioning to a doctor.

NICE also points out that people from some ethnic minority backgrounds and people with some lifelong conditions may reach menopause at a younger age.⁴

NICE recommends offering psychological support to women who are distressed by early menopause between 40 and 44.⁴

What changes the timing

Smoking has the clearest effect. In the Massachusetts study, current smokers reached menopause about 1.8 years earlier than non-smokers, and their perimenopause was also shorter.¹ Surgery, some medical treatments and some inherited conditions can bring menopause earlier too.⁴

Researchers describe the transition in stages, using a system called STRAW+10: an early stage and a late stage of the transition, defined by changes in bleeding patterns, then early and late postmenopause. The system applies regardless of a woman's age, ethnicity, body size or lifestyle.⁵

Early perimenopause symptoms covers the first signs, perimenopause symptoms the full list, and is there a test for perimenopause why blood tests rarely settle it.

Why your forties are the decade to act

Muscle and bone start changing during perimenopause, not after it. In SWAN, lean mass began to fall and fat gain sped up during the transition.⁶ Bone loss then speeds up for 4 to 8 years after menopause.³

That makes the years around 45 a good time to put three habits in place:

1. Strength training two or three times a week.
2. Protein at every meal, about 25 to 30 g, with a daily total based on your weight.
3. Enough calcium and vitamin D, mostly from food.

Protein is the one most women underestimate. Protein Buddy works out a daily target from a short quiz on your weight, age, activity and goal, and Home shows how many grams are left today as you log. Typing meals in by hand is free with no limit. Protein for women over 40 explains why the target matters more in this decade.

Ovulation in perimenopause explains how ovulation changes across these years.

When to see a doctor

See a doctor if your periods stop or change a lot before 45, if bleeding becomes very heavy or happens between periods, or if symptoms are affecting your sleep, mood or work. Signs perimenopause is ending covers the last stretch. Keep using contraception until your doctor tells you it is no longer needed: NICE advises clinicians to give contraception information to people with menopause symptoms.⁴