A guide to your menstrual cycle

What the menstrual cycle is

The menstrual cycle is a repeating process that prepares the body for a possible pregnancy. It's counted from the first day of one period to the first day of the next.

For adults, a cycle of 24 to 38 days is considered usual, with up to 8 days of bleeding. It's normal for the length to shift a little from month to month; if your cycles differ by more than 7 to 9 days, it's worth raising with your doctor. Very few women have cycles of exactly 28 days.

In the teenage years and the years before menopause, cycles tend to be less regular. So rather than comparing yourself with an average, the most useful thing is to learn your own rhythm.

The phases, one by one

Medicine usually describes three phases: follicular, ovulatory and luteal. Your period happens at the start of the follicular phase. To make it easier to follow, we treat it here as a moment of its own.

1. Menstruation

   From the first day of bleeding

   If there was no pregnancy in the previous cycle, estrogen and progesterone fall and the lining of the uterus sheds: that's your period. Cramps, tiredness or wanting to slow down are common.

2. Follicular phase

   From the start of your period until ovulation, about 13 to 14 days on average

   Follicle-stimulating hormone (FSH) causes several follicles in the ovaries to grow. One becomes dominant and makes estrogen, which rebuilds the uterine lining. This phase varies the most in length, and it's the main reason some cycles are longer than others.

3. Ovulation

   Usually 10 to 16 days before your next period

   A sharp rise in luteinizing hormone (LH) makes the dominant follicle release an egg. In the days before, vaginal discharge often becomes clearer and more slippery, and some women feel a mild twinge on one side of the pelvis. The egg can only be fertilized for a matter of hours, but sperm can survive for several days, which is why the fertile window includes the days before ovulation.

4. Luteal phase

   About 14 days, until your next period

   The empty follicle becomes the corpus luteum, which makes progesterone and estrogen to prepare the uterus. If there's no pregnancy, the corpus luteum shrinks, hormone levels fall and a new period begins. This is when premenstrual symptoms appear, if you get them.

These lengths are approximate. A diagram helps explain the process, but your cycle may not follow it to the letter.

Hormones: who does what

The cycle is coordinated between the brain and the ovaries. Four hormones do most of the work:

FSH (follicle-stimulating hormone)

Sent by the brain early in the cycle so follicles in the ovaries mature.

Estrogen

Made by the follicles. It rebuilds the uterine lining and, once it reaches a certain level, sets off the LH surge.

LH (luteinizing hormone)

Its sudden surge triggers ovulation.

Progesterone

Made by the corpus luteum after ovulation. It prepares the uterus and thickens cervical mucus.

Why every woman experiences it differently

These hormonal shifts happen in everyone, but each body responds in its own way. Sleep, stress, food, exercise, medication and other health conditions all play a part. That's why two women with similar cycles can feel very different, and why your own symptoms can change from cycle to cycle.

A cycle that varies doesn't mean something is wrong. What's worth checking with a professional is a clear change from what's normal for you, or symptoms that get in the way of daily life.

Common symptoms and what's worth knowing

The same symptom can have different causes. This guide helps you recognize them; it can't diagnose them. If a symptom is strong, lasting or worries you, get it checked.

How to observe your cycle

Observing your cycle means writing down what you experience so you can recognize your patterns. It doesn't replace a medical evaluation, but it makes one more useful: you arrive with information instead of scattered memories.

1. Note the first day of each period. It's the most important detail: it tells you how long your cycle is.
2. Record how many days you bleed and what the bleeding is like: amount, color and clots.
3. Write down your symptoms and how strong they are, with the day they appear: pain, mood, energy, sleep, appetite, skin, discharge.
4. After two or three cycles, look at the whole picture. Do some symptoms repeat in the same phases? Has anything changed from your usual?
5. Bring a summary to your appointment. Dates, cycle lengths and main symptoms help your doctor understand your situation faster.

You can use a notebook or Ovulonas, the CÍCLICAS app, which also shows your patterns and prepares a summary for your appointment.

Questions worth asking at your appointment

Appointments are often short. Bringing your questions written down helps you make the most of yours.

• Is what I'm experiencing within the expected range for my age and stage of life?
• What could be causing this symptom, and how can we look into it?
• Which tests do you recommend, and what is each one looking for?
• What changes in my symptoms should bring me back sooner?
• How might my medication or birth control method affect my cycle?
• What should I keep writing down before the next visit?

When to see a health professional

• You haven't had a period in 3 months and you aren't pregnant, breastfeeding, or in perimenopause or menopause.
• Your cycles become irregular, very frequent or far apart.
• Bleeding lasts more than 8 days, or you soak through a pad or tampon every 1 to 2 hours.
• You pass clots larger than a quarter.
• Pain doesn't improve with over-the-counter pain relievers.
• You bleed between periods, after sex more than once, or after menopause.
• Symptoms before your period affect your work, studies or relationships.

Get medical care right away if during or after your period you have chest pain, trouble breathing, strong dizziness or weakness, or if you develop a sudden fever and feel sick while using tampons.