Most Australians get their first period at 12 or 13, says healthdirect, although anywhere from 9 to 16 is possible, and anyone who hasn't started by 16 or 17 should talk to a doctor. Those early cycles can be long: the Better Health Channel notes that teenagers may have cycles of about 45 days, while people in their 20s and 30s usually sit between 21 and 38.
So understanding your menstrual cycle is less about matching a textbook 28 days and more about learning your own rhythm. Here is how the cycle works and when to get it checked.
Quick answer: Your menstrual cycle is the hormone-driven pattern that prepares your body for a possible pregnancy, counted from the first day of one period to the first day of the next. Healthdirect says periods usually come 21 to 35 days apart, and most people bleed for 3 to 7 days, with the heaviest flow at the start.
How many days apart should my periods be?
Periods usually arrive between 21 and 35 days apart, and healthdirect points out that the gap varies from person to person and even from one cycle to the next. To find your number, count from the first day of a period up to the first day of the following one. The Better Health Channel gives 28 days as the average but stresses that everyone's cycle is different.
What happens during each phase of the cycle?
The cycle is controlled by hormones released by the brain, the ovaries and the uterus. The Better Health Channel describes four phases:
- Period: the uterus lining sheds and flows out through the vagina as a mix of blood, mucus and cells from the lining. On average this lasts 3 to 7 days.
- Follicular phase: begins on day one of your period and runs for 13 to 14 days. Changing hormone levels thicken the lining and grow follicles on the surface of the ovary, and usually just one of them matures into an egg.
- Ovulation: the mature egg is released, normally once a month and roughly 2 weeks before your next period. This is when unprotected sex carries the highest chance of pregnancy.
- Luteal phase: the egg moves through the fallopian tubes towards the uterus while the lining keeps building. If you don't become pregnant, your period starts and the cycle begins again.
If you'd like more detail on the fertile window, read can I get pregnant when I'm ovulating.
What are the signs my period is coming?
Healthdirect lists a range of physical and emotional changes that can show up before and during a period:
- cramps or aches in the lower tummy or back;
- bloating, constipation or diarrhoea;
- headaches, acne and tiredness;
- sore or swollen breasts;
- mood swings and feeling irritable.
Some people barely notice anything, while others find these symptoms make daily life hard. For ideas on easing them, see how to deal with PMS.
How do I keep track of my cycle?
Write down the first day of each period and count the days until the next one starts. Healthdirect also suggests keeping a list or diary of your symptoms to bring along when you see a doctor, so you can show what has actually happened instead of relying on memory.
When to see a doctor
Healthdirect and the Better Health Channel recommend talking to a doctor if:
- your periods change pattern, become heavier than usual, or you need a new pad or tampon more often than every 2 hours;
- a period lasts more than 8 days;
- periods come less than 21 days apart, or more than 2 to 3 months apart;
- your periods have stopped for more than 6 months and you're not sure why;
- you bleed between periods, after sex, or after menopause;
- period pain is severe enough to disrupt daily activities;
- you are 17 and haven't had a period yet;
- your periods affect your wellbeing or enjoyment of life, or you feel something isn't right.
Frequently asked questions
Why are my cycles so long as a teenager?
Long cycles are common in the first years. The Better Health Channel says teenagers may have cycles lasting around 45 days, which tend to settle closer to 21 to 38 days in your 20s and 30s. If you are 16 or 17 and your periods haven't started at all, healthdirect recommends speaking with your doctor.
Is a 28-day cycle the only normal one?
No. Twenty-eight days is simply an average. Healthdirect describes periods arriving anywhere from 21 to 35 days apart as usual, and the gap can shift a little between cycles. What matters more is a sudden change in your own pattern, which is worth mentioning to a GP, especially alongside new pain or heavier bleeding.
Who can I call about my period after hours?
You can phone healthdirect on 1800 022 222 to speak with a registered nurse 24 hours a day, 7 days a week; in Victoria the service is called NURSE-ON-CALL. If you ever need urgent medical help, call triple zero (000) straight away rather than waiting for a callback.
Getting to know your rhythm is easier when you can see your flow. The Lunette period cup has measuring lines inside, and Lunette suggests Size 1 for teens and a light to medium flow, Size 2 for a heavier flow or higher cervix. Compare both in the size guide before choosing your first menstrual cup.
This information is general in nature and isn't medical advice. For questions about your own cycle, speak with your GP or call healthdirect.
