Most women menstruate for between three and seven days each month. When our period is late or unusually light, it's natural to get a bit worried!

While it's always wise to check with your GP or pharmacist if you're panicking, keep in mind that pregnancy or illness aren't the only reasons behind irregular periods.

Here are a few causes that you might not have known about…

1. Stress
When we are overly stressed, anxious or run-down, our body can go through a series of hormonal changes which can mess up our cycle or stop it completely. Extreme stress can also lead to other problems like bad digestive function, abdominal or muscle pain and heart palpitations.

2. Dietary changes
A severe drop in weight can lead to irregular or missed periods, but so too can weight gain. A diet heavy in fat and carbs can mess up our hormonal function as much as a diet which is lacking in fat.

3. Over-exercising
Our body needs energy to perform basic functions, one of which is menstruation. If you're wearing yourself out at the gym you may notice that you begin missing periods.

4. Use of the Pill
If you have just stopped or started using the Pill for the first time, it will take a while for your body to get back on track, so don't worry if your period arrives later than usual.

5. Alcohol
Our liver is responsible for metabolising oestrogen and progesterone. Excessive alcohol consumption can damage liver function leading to a whole host of problems, one of which is irregular or missed periods.

6. Use of antibiotics
Certain prescription and over-the-counter medicines can cause a hormonal imbalance, meaning your period may arrive a day or two late.

7. Lack of iron
A common symptom of iron-deficiency anaemia is missed or extremely light periods. You may also start feeling overly tired and week. If you suspect you may be anaemic, do consult your GP for tests.