From pregnancy to daily stress & hormone imbalance, here are seven reasons your period may be late

Did your period arrive later than usual this month? It’s normal to be concerned when your menstrual cycle changes, especially if you’re worried about an unplanned pregnancy. While pregnancy is one explanation for a missed period, there are several other factors which can cause your period to be late, and they all relate to the balance of hormones in your body. 

The average menstrual cycle lasts 28 days, but this can range from woman to woman between 21 days to 35 days. There are also two other times in a woman’s life where irregular periods are expected – during puberty and the menopause. 

What is considered a ‘late’ period?

It’s not uncommon for some women’s cycles to vary from month to month by about seven to nine days. Variation within this timescale doesn’t necessarily mean that their period is late or they’ve missed a period – there could be a number of lifestyle factors that have affected it. 

If you are somebody with a very regular cycle and your period arrives nine days after the expected date, this would be considered late. 

What can cause a late period?


It should come as no surprise that daily stress is one of the most common reasons for your period arriving late. Stress can wreak havoc on your hormones, upsetting the balance needed to keep your body functions running as they should. Your body may postpone your period until the level of the stress hormone (cortisol) in your body has lowered.

Ironically, your period arriving late may only cause you to feel even more stress. Relaxation techniques such as mindfulness and meditation or gentle exercises like running, yoga or swimming can help you take a moment to yourself and reduce your stress levels.

Your body weight

Sudden weight loss or change in your body weight can affect your ability to ovulate, which will lead to a late or missed period.

Rapid weight loss or severely restricting your calorie intake can stop your body from producing the hormones you need to ovulate, which can cause the menstrual cycle to halt. Similarly, excess weight gain may cause you to produce too much oestrogen, one of the hormones that helps regulate the reproductive system in women. This can cause irregular periods or for them to stop altogether. 

Doing too much exercise

Intense physical activity can put stress on your body and upset your hormone balance. In some circumstances, this can prevent you from ovulating and cause you to miss a period. Losing too much body fat can also contribute to this.

If you’re a professional athlete and wish to maintain your performance without disrupting your periods, consult a doctor who specialises in sports medicine for advice.

Your birth control

Changes to your cycle can happen when you start or stop using some types of birth control.

Some contraception methods, like birth control pills, use oestrogen and progestogen to prevent your ovaries from releasing eggs. The change in hormone levels in your body can cause your period to arrive late or become irregular while your body tries to adjust. Some birth control types, such as the IUS (hormonal coil) can cause your periods to stop all together. 

For some women, it can take up to six months for your cycle to find a regular pattern after first starting or stopping a method of contraception. 

Chronic illnesses and medical conditions

Some medical conditions, like polycystic ovary syndrome (PCOS) can cause your periods to stop as it has an effect on the levels of hormones in your body. If you’re concerned that an underlying health issue is affecting your period, speak to your GP. 

Menopause & early perimenopause

Menopause is a natural part of ageing in women. Your oestrogen levels will begin to decrease, and ovulation (and your periods) will become less regular. Eventually, your periods will stop completely.

Most women begin the menopause between the ages of 45 to 55, however there are some people who begin to experience the symptoms of menopause (known as perimenopause) earlier than this, around the age of 40. You should also see your GP if your periods stop before you're 45. 


If you’re sexually active and your period is more than a week late, pregnancy could be the cause. You can become pregnant if you’ve had unprotected sex since your last period, or if the contraception you’re using fails.

Wait a few days to see if your period arrives, and if not, take a home pregnancy test or visit your GP to determine whether you are pregnant. 

Can I delay my period?

If you have a big event coming up or a holiday where you’d prefer to be period-free, you can visit the Boots Online Doctor Period Delay Service*. Simply complete an online consultation and a clinician will review your answers within 24 hours, provide advice and prescribe medication to delay your period if suitable for you

When is it time to see a GP?

You should see your GP if you’ve had a negative pregnancy test and you’ve missed more than three periods in a row.

It’s also important to see a GP or a medical professional if you’re experiencing:

• Unexpected heavy bleeding

• Severe pain

• Vomiting and nausea

• Dizziness

• High fever

• Pressure in the lower abdomen

If your period is late, rest assured that your body doesn’t always work like clockwork and it’s natural for there to be some shift in your cycle from month to month. If you’re worried that an underlying health issue may have caused you to miss a period, or that you might be pregnant, speak to your GP for advice. It never hurts to be prepared either – keep some feminine hygiene products in your bag so you aren’t caught out if your period starts unexpectedly!

*Subject to availability and clinician approval. Charges apply.