What's a normal menstrual cycle and what's not?

Morag Martindale

GP and expert in baby and women's health.

It's hard to say what's normal, as every woman has a cycle that is unique to her. A normal menstrual cycle could be as short as 22 days or as long as 36 days. When doctors talk about the length of your cycle, they include the days when you have your period.

If you have a regular 28-day cycle you will start your period every four weeks. If you have a 22-day cycle you'll have a period about every three weeks. The average period lasts for three to four days, but it can be shorter or longer, ranging from between one and seven days.

Most women ovulate between 12 and 14 days before their period. This is an average, so it could be a few days sooner or later than this. If you have a 28-day cycle, you will probably ovulate in the middle of your cycle. If you have a 22-day cycle, you could ovulate just a few days after your period.

If you have regular periods then it is fairly easy to work out when you are likely to be ovulating. If your periods are irregular, it's not as easy to tell when you’re at your most fertile. If you're trying to get pregnant, it may help if you keep a record of when you have your periods for a few months.

Regular periods or not, if you are trying for a baby, you will boost your chances of conceiving by having sex every two to three days throughout your cycle. It will also be less stressful than concentrating all your baby-making efforts around the time you think you are about to ovulate.

If your periods are very irregular, you may not be ovulating at all, or infrequently. Again, keep a record of the dates that you have your period.

It's a good idea to make an appointment with your doctor if:

  • You've not become pregnant within a year of trying, as long as you've been having sex two or three times a week.
  • You have bleeding between periods, or after sex.
  • You are aged over 36.
  • You have a known problem that could affect your fertility.

That way, your doctor will be able to look into why you're not conceiving and explain the options that are available to you.


This article was written using the following sources:
CKS. 2007. Infertility. Clinical Knowledge Summaries, Clinical Topic. [Accessed August 2011]



NHS Choices. 2010. What causes bleeding between periods? NHS Choices, Health A-Z. [Accessed August 2011]

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