# Your cycle through life

> From the first period to menopause: what changes, and when.

Category: Cycle basics · 4 min read · Written by the Splash team · Sources checked October 2026
URL: https://splash.care/learn/cycle-basics/cycle-through-life

## Quick answer

- Teens often have longer, irregular cycles for a few years.
- Cycle length tends to drift a little shorter with age, then becomes irregular in perimenopause.
- The average age of menopause in the UK is 51, but changes usually start earlier.
- Any bleeding after menopause should be checked.

Your cycle is not a fixed setting. It changes with your life stage, just like your skin or your [sleep](https://splash.care/learn/movement-sleep/sleep-cycle). Knowing what is typical at each stage can help you tell "this is just my age" from "this is worth a check".

## Teens: finding a rhythm

The NHS says periods usually begin around 12 and most people have regular periods by 16 to 18. ACOG says cycles of 21 to 45 days are normal for teens and it can take several years to settle. Heavy or very painful periods are still not something to put up with.

## 20s and 30s: your own pattern

In a study of over 600,000 cycles, average [cycle length](https://splash.care/learn/glossary/cycle-length) got slightly shorter with age (about 3 days shorter between the youngest and oldest groups), and the spread between one person's own cycles also got smaller as age rose through the late 20s and 30s. Hormonal [contraception](https://splash.care/learn/contraception/methods-overview), [pregnancy](https://splash.care/learn/fertility-ttc/early-pregnancy-signs), breastfeeding, [stress](https://splash.care/learn/cycle-basics/stress-travel-illness) and medical conditions can all rearrange things in this stage of life.

## Perimenopause: the shake-up

The NHS says [menopause](https://splash.care/learn/glossary/menopause) and [perimenopause](https://splash.care/learn/glossary/perimenopause) usually affect people between 45 and 55, and the UK average age of menopause is 51. Periods usually do not just stop suddenly. They tend to get less frequent over months or years. Some people notice shorter cycles or heavier bleeding first, then longer gaps.

- **Menopause** is a point in time: 12 months with no periods (NICE uses this if you are 45 or over and not on hormonal contraception).
- **Perimenopause** is the run-up, when [hormone](https://splash.care/learn/cycle-basics/hormones-explained) levels fluctuate.
- **After menopause**, any vaginal bleeding needs checking by a GP.

> **Splash says:** if your cycle changes after 40, note it. A record of dates and flow helps a GP tell perimenopause from other causes.

**Myth:** Periods stop suddenly at menopause.

**Fact:** Most people see months or years of irregular, lighter or heavier periods first. Periods that suddenly become very heavy, or bleeding between periods, should still be checked.

### When to see a doctor

See a GP for bleeding after menopause, bleeding between periods or after sex at any age, periods that become much heavier or last longer than 7 days, or cycle changes together with symptoms that bother you.

## Sources

1. [NHS: Periods](https://www.nhs.uk/conditions/periods/)
2. [NHS: Starting periods](https://www.nhs.uk/conditions/periods/starting-periods/)
3. [ACOG: Your first period](https://www.acog.org/womens-health/faqs/your-first-period)
4. [NHS: Menopause and perimenopause](https://www.nhs.uk/conditions/menopause-and-perimenopause/)
5. [NICE NG23: Menopause: identification and management](https://www.nice.org.uk/guidance/ng23/chapter/Recommendations)
6. [Bull et al. (2019) Real-world menstrual cycle characteristics of more than 600,000 menstrual cycles, npj Digital Medicine](https://pmc.ncbi.nlm.nih.gov/articles/PMC6710244/)

This is general information, not medical advice. Splash can’t diagnose. If you’re worried, talk to a GP, pharmacist or sexual health clinic. In an emergency call 999 (UK) or 911 (US).