Well, you could be pregnant. That’s the obvious one. But if you’ve ruled that out (and even if you haven’t), there are a whole heap of other reasons your period might be late – or even MIA. Here’s what they are.

1. You’ve just started

It’s normal to be irregular when your periods first begin and chances are you’ll get used to your cycle being a different length each month. As you get older, things will settle into a more predictable pattern.

2. Stress

Trouble at work, health worries or simply a change your daily routine can cause stress, which sends your hormones do-lally. This can lead to changes in the frequency and duration of your period. See more here about how COVID-19 has affected some women’s cycles.

3. The skinnies

If you weigh more than 10 per cent below what’s considered normal for your height, this can stop you ovulating, in which case, no period necessary. This can include people with eating disorders, but also those who do intense levels of exercise, such as marathon running.

4. Obesity

On the flip side, being overweight impacts hormone and insulin levels, which can interfere with your cycle. Rapid weight gain especially can cause irregularities. Unexplained weight gain and irregular periods are side effects of PCOS (see below) and hypothyroidism (see below also), so see a doctor to rule them out.

5. PCOS

Polycystic ovary syndrome is a condition caused by the body producing excess of a hormone called androgen – AKA hyperandrogenism. It basically stops you ovulating regularly and can lead to (often treatable) fertility issues. Consider your unpredictable periods an early warning system.

6. Thyroid issues

The thyroid regulates your body’s metabolism, and in turn its hormone levels. An overactive or underactive thyroid can therefore be the reason for a late or missed period. With treatment, things will quickly return to normal.

7. (Early) menopause

Before menopause sets in for good, there are a few years called ‘peri-menopause’ when your fertility starts to drop. It usually happens in your 40s, but can be earlier. This is the other time in your life (see #1) when it’s totally normal to have erratic periods.