The Independent Pharmacy

Possible Causes of Delayed Periods

Scott McDougall
Scott McDougallMPharmDirector & Registered Manager

Reviewed on 13 Dec 2022

This isn’t usually a cause for concern, as there are many factors that can impact the commencement of a period. Even so, it’s good to know what these factors are so you can feel confident interpreting your cycles.

How much period delay is normal?

While it’s normal for a woman to have a period every 28 days or so, it’s not uncommon for one to experience a slightly shorter or longer cycle (anywhere between 21 and 40 days). Furthermore, some women will experience irregular or skipped periods. Keeping track of when your periods occur is a good way to determine the normal length of your cycle and spot any irregularities.

Generally, any period that begins between 1 and 4 days earlier or later than usual is considered normal. Now, that doesn’t necessarily mean a period that’s delayed for longer than this should be a concern, but if your period hasn’t arrived within 5 days of the expected commencement then it may warrant further investigation. A period is only considered to be missed when you’ve experienced no menstrual flow for at least 6 weeks following the start of your last period.

What can delay your period?

There are a number of possible causes of a delayed or missed period, most of which are not cause for undue concern. Reasons for delayed periods can include:

  • Pregnancy. If you’re sexually active and your period is delayed, it may be because you’re pregnant (even if you’re using contraception, as this is not always 100% effective).
  • The contraceptive pill. Taking the contraceptive pill can cause you to occasionally skip a period, and this is usually nothing to worry about. If you’re taking a progestogen-only pill (POP), this can cause your periods to stop altogether.
  • Menopause. As you approach menopause, your periods may become less regular due to decreased oestrogen levels. Post-menopause, your periods will stop altogether.
  • Fast weight loss. Drastically reducing your calorie intake can prevent the production of hormones needed for ovulation, delaying your period.
  • Being overweight. Being overweight can cause your body to produce excess oestrogen, affecting your periods and potentially even causing them to stop.
  • Polycystic ovary syndrome (PCOS). PCOS is a fairly common condition that causes the ovaries to produce an abnormal amount of androgens. It can lead to irregular or delayed periods, or in some cases no periods at all.

Periods can also stop due to other medical conditions such as diabetes, heart disease or an overactive thyroid. In any case, you should consult your GP if you’re concerned about a missed or delayed period — particularly if you’ve missed more than 3 periods in a row despite having a negative pregnancy test.

Can stress delay your period?

Stress can shorten or lengthen the menstrual cycle (or even cause periods to cease altogether) and is therefore a common cause of a delayed period. To reduce stress, make time to relax, exercise regularly, and try practising breathing exercises.

Can antibiotics delay your period?

Taking antibiotics shouldn’t have any impact on your menstrual cycle, so they’re not likely to be the cause of a delayed period. Nonetheless, you should speak to your doctor if you think there may be a link between a delayed period and any antibiotics you’re taking.

Can the morning-after pill delay your period?

Taking the morning-after pill may cause your period to be delayed by up to a week. If your period is delayed by 3 or more weeks after taking the morning-after pill, take a pregnancy test or speak to your doctor.

Can a smear test delay your period?

Having a smear test should not affect your menstrual cycle in any way. It’s normal to experience a little bleeding or spotting after having your smear, but it won’t cause a delayed period.

Can a yeast infection delay your period?

Although it’s often assumed that a yeast infection can cause a delayed period, there’s no medical evidence to suggest this is the case. You should treat your yeast infection as advised and consult your GP if you’re at all concerned.

Can having a cold delay your period?

Mild-to-serious illnesses can affect hormone levels and destabilise your menstrual cycle, so a common cold or the flu could in some cases cause your periods to be delayed or missed. You should treat any ailments as normal and speak to your doctor if you have any concerns.

What to do if your period is delayed

A delayed period is not always cause for concern. Not all women experience regular menstrual cycles, so it may be normal for your period to arrive a few days early or late, and an untimely period will typically be otherwise normal. Even so, if you’re worried about an irregular, delayed or missed period, you should speak to your GP for advice.

If you’re sexually active and your period is delayed for more than a few days, you should take a pregnancy test to determine whether you’re pregnant. Even if you’re using contraception, you should take a test to be doubly sure (contraception can sometimes fail).

Should I see a doctor for a delayed period?

If you know you’re not pregnant (i.e. you’ve had a negative pregnancy test) but you’ve missed 3 or more periods, you should see your GP. If your GP thinks your missed periods may be caused by an underlying medical condition, they’ll likely refer you to a specialist such as a gynaecologist or an endocrinologist.

Of course, if you have any concerns at all about a delayed or missed period (or you’re experiencing period pain), you should speak to your GP for advice. It’s likely there’s no reason to be concerned but getting an expert opinion will help determine the root cause of your delayed period and gauge whether there’s a need for treatment or referral.

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