The menstruation cycle is something many people might have heard a lot about in sexual education in school, but not much more after that. Even if you are seeking pregnancy or are trying to avoid it, a good knowledge of your cycle will be helpful.

What’s on this page?

What is a menstrual cycle?

The menstrual cycle is a more medical term for the process of getting your period. Most people get their period in regular patterns, with menstrual bleeding during 3-8 days and with 21-35 day between periods.

The uterus has a mucous lining that will once a month grow and become thicker and richer in blood vessels. If you have not become pregnant, this thickened lining will shed and is transported out of the body through what we experience as a menstrual bleeding.

When do you ovulate? 

The menstrual cycle is triggered by an array of hormones, of which many stem from the pituitary gland and hypothalamus in the brain together with the ovaries. Two important hormones are oestrogen and progesterone. They create a reaction in the ovaries and uterus, where they act together to make eggs mature for fertilization and create a thickened womb lining. If no pregnancy has occurred, the hormone levels will drop and cause the urethral mucous to shed and you will get your period.

Day of the cycle Cycle stage
Day 1-5 Menstruation – will normally last between 3-8 days
Day 6-14 The uterine lining will become thicker
Approximately day 14 Ovulation – an egg is released and can be fertilized
Day 14-28 If no fertilizarion has occured, the uretral lining will prepare to begin shedding

The menstrual cycle – the details

The menstrual cycle is bound to these two mechanisms taking place in the follicles of the ovary and the endometrial lining of the uterus.1 They are both divided into three stages that are covered below.

The cycle of the ovary

The first stage is the follicular phase. At the beginning of the phase occurring during the first 14 days of your cycle, you will be having your period, but simultaneously the follicles are preparing for the next ovulation. The levels of oestrogen will be raised, which gives a reaction in the ovaries. The follicles are responsible for releasing the eggs, and during this phase, they mature to be able to do this. This process involves follicle stimulating hormones that will spur the follicles to rise to the surface of the ovary to grow. One follicle will become dominant, which makes the other follicles stop in their growth. The dominant follicle will be the one releasing an egg that later can be fertilized.

Ovulation is the next stage where a hormone is released to weaken the follicle and releases an underdeveloped egg cell. This happens approximately on the 14th day of the cycle. If it would be fertilized by a sperm it will fully develop into a complete egg, but if not, it will degenerate within 24 hours. Some women experience some pain during this process.

The womb contains two ovaries where this process can take place, and mostly the process is altering between the two. Sometimes the ovulation occurs in both of the ovaries, and if they both would be fertilized it results in twins.

The last part of the cycle is the luteal phase. Here, the levels of the hormone progesterone will drop and approximately two weeks after ovulation, the hormone drop causes the uterus to shed the mucous lining and gives you menstruation.2

The cycle of the uterus

Menstruation is the first stage of this cycle, when the womb is shredding somewhere between 10-80 millilitres of blood, with 35ml on average. It is during the onset of this phase that some women suffer from the premenstrual syndrome with period cramps.

Then there is the proliferative phase, where the hormone oestrogen will cause the mucous lining of the uterus to grow.

This is followed by the secretory phase where the uterus more or less prepares for an early pregnancy if one should occur. During this period the basal body heat will be raised.

Menstrual cycle and contraception

Contraceptive pills are based on the hormones oestrogen and/or progestogen with the ratio and concentration of these hormones varying depending on the exact type and brand of the pill. The main function of these pills is to prevent ovulation, so the egg is absent and the woman cannot conceive as long as she continues the treatment. In addition, the hormones also affect the cervical mucus, making it harder for the sperm cells to reach the egg. And finally, by affecting the uterus, contraceptive pills make it physically more difficult for the egg to get stuck.

Read more about different forms of contraception here.

Can I control when I get my period?

Many people using hormonal contraceptives such as the birth control pill experience that their period is sticking to a more predictable pattern and feel more in control over their period. In some cases, you can delay your period if you believe that your period will come at an inconvenient time.

When you want to delay your menstrual period, this can be done using an artificial hormone called norethisterone. This hormone also exists in various forms of contraception such as mini pills and hormone treatment for menopause.

Norethisterone is an artificial version of the hormone progesterone. When artificially added to the body, it will believe that the uterine lining still needs to mature and get ready for an egg. Therefore, there will be no rejection of the mucous membrane, and this helps to delay the menstrual period.

Read more about how to delay your period here.

Is my bleeding normal?

Bleeding is considered abnormal when more than 80ml is lost, since heavy bleeding beyond this point comes with a risk of anaemia. Some women lose much more blood. Bleeding more than a litre each month has been recorded, but this is very unusual. 

A complete lack of periods could be caused by hormonal imbalances, lifestyle factors, medication, underlying conditions and much more. Sometimes the cycle can be restarted with hormonal therapy.

If your periods are vanished, causing you trouble in your everyday life or if you suddenly bleed more than normal you can consult a GP or ob-gyn to plan a treatment for you.


  1. More on the cycle – NHS
  2. More on the process – Your Period