Periods

Normal Periods

Every month, your womb lining (endometrium) thickens with blood to provide the perfect conditions for a foetus to grow. But if no egg is released, or an egg is released but not fertilised (does not connect with sperm), the body sheds the womb lining.

This blood and tissue loss is known as your menstrual period, which you would have started sometime between the ages of 12 and 16. On average, you have a period every 28 days, but menstrual cycles can vary from 24 to 35 days (day one is the first day of your period).

Keeping track of your cycle in a diary will give you an idea of how regular it is. Sometimes, your cycle may change from month to month. Here are some of the reasons why.

Missed Period

Pregnancy is the most common cause of a missed period so it's always worth eliminating this first with a pregnancy test. A DIY test costs around £4 to £5 from supermarkets or pharmacies, or you can get a free (and confidential) test from your GP or local FPA clinic.

Erratic eating habits can cause missed periods, particularly if you're not eating enough. Your body won't produce enough of the female sex hormones it needs if it's undernourished, and this can be a sign of anorexia. Missed periods are common in those with a Body Mass Index of less than 19 (calculate your BMI).

Over-exercising can also cause missed periods, especially in women competing in sports, such as athletics or gymnastics, which require you to have low levels of body fat. If your body fat drops below 16%, the ovaries will stop producing oestrogen, so you won't have periods. If this is happening to you, talk to your GP about a referral to a registered dietician, as it may lead to an increased risk of osteoporosis in later life.

PCOS (polycystic ovarian syndrome), when small, fluid-filled sacs form on the ovaries, can disrupt the menstrual cycle. The changes in hormone levels caused by PCOS (including increased levels of testosterone) can cause missed or lighter periods. Other symptoms include acne and increased body hair. An ultrasound test can detect PCOS, and treatment usually combines lifestyle changes with medication.

Sometimes, women who are very overweight will miss periods. It's thought that high levels of body fat increase levels of testosterone in the body, which can affect the balance of the female sex hormones oestrogen and testosterone. Visit the NHS website for more advice on healthy eating and weight loss.

Sometimes, missed periods are a sign of an overactive thyroid (hyperthyroidism). If you have other symptoms, such as weight loss, anxiety and excessive sweating, see your GP for a blood test.

Late Period

Pregnancy is the most common cause for late periods, so check this out with a DIY, GP or clinic test. Coming off the pill can also cause late periods - it can take up to six months for your cycle to settle.

Prolonged periods of stress or emotional upheaval can have a similar effect. It's thought that over-production of stress hormones, such as cortisol, may interfere with levels of the female sex hormones oestrogen and progesterone.

Learning to relax with simple breathing exercises can help - go and sit in a quiet, calm place and breathe into your stomach (if you push your stomach out as you breath in, your diaphragm pulls down, allowing your lungs to fill up to their full capacity) for five slow, steady counts. Pause for a second, then breathe out steadily for the count of six or seven, and pause again for a few seconds. Repeat five times, or as many as you need to feel calm.

Early Period

When you’ve just started your periods, your cycle can be erratic, and may take a year or two to settle down. Your periods can also be irregular for up to six months after coming off the contraceptive pill.

Your menstrual cycle tends to get shorter in the years leading up to the menopause so you may find your periods come more often. (If you want to read up on menopause symptoms or suspect you may be experiencing early signs, read our article on the perimenopause.)

See your GP if your cycle is regularly shorter than 21 days (from the start of one period to the start of the next). Having periods too often may put you at risk of becoming anaemic so make sure you speak to your doctor if you are at all worried.