Can Antibiotics Make Your Period Late or Affect Them at All?

Antibiotics are the standard treatment for bacterial infections, but some women may notice that their period is late after taking them. This can lead many to wonder if antibiotics have any effect on your menstrual cycle, and if they can cause a period to be late.

While a natural thought process, antibiotics, in general, do not have any effect on menstrual cycles. Instead, the cause of the late period is often related to the illness the antibiotic is prescribed to treat.

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Can Antibiotics Make Your Period Late?

While it is not uncommon to experience a late period after taking antibiotics, research has shown that antibiotics have no effect on your period’s timing and are thus not responsible for a late period.

However, despite these current understandings, emerging evidence shows that alterations of the gastrointestinal tract from antibiotics may affect the menstrual cycle. 

As we know, antibiotics kill bacteria causing your infection, but in some cases, they may also kill the good bacteria in your gut and disrupt your gut. Furthermore, a 2017 article found that microorganisms in the gut produce beta-glucuronidase, an enzyme that can impact estrogen levels. Estrogen is one of the main drivers of a menstrual cycle, so the theory is that an imbalanced microbiome (in this case, due to antibiotic use) might result in lower estrogen levels, which could then result in an irregular period.

However, there is not a lot of data to support the effect of this enzyme on estrogen levels, so we can’t yet say that antibiotics are related to late periods. For now, this potential connection is only speculation, and the greater evidence is research showing that antibiotics do not cause periods to arrive late. 

Can Antibiotics Affect Your Menstrual Cycle at All?

Antibiotics generally do not have any real impact on the menstrual cycle. The only exception is rifampin, an antibiotic used to treat tuberculosis which has been shown in some studies to affect periods.

While antibiotics are unlikely to affect your period, being sick, which is a cause for antibiotics, can affect it, causing changes such as:

  • heavy bleeding
  • light bleeding
  • early periods
  • shorter periods

In fact, it’s more likely that these period changes are from the other medications you may be taking while sick to feel better, such as ibuprofen or aspirin. These over-the-counter pain relievers have been known to cause changes to menstrual bleeding and might be the culprit behind your different menstrual cycle.

Can Antibiotics Affect Your Period Symptoms?

Antibiotics have not been shown to have any influence on your period. However, the side effects of illness may make your period symptoms worse. For example, fever can cause dehydration, which can make symptoms such as cramps, bloating, fatigue, and headaches worse. 

What Else Could Be Affecting Your Menstrual Cycle?

While we know that antibiotics cannot cause a period to be late, there is no denying that many women experience a late period after completing a course of this medication. So, what is the cause of these late periods? Let’s take a look.


Stress is a common culprit for a late period, and it is also likely that, while taking antibiotics, you’re stressed. Not only are you likely to be stressed about being ill, but illness may also cause you to cancel plans or miss work, which can further increase your stress levels.

A study found that 27% of adolescent girls experience a late period due to stress, so if your period is late, this might just be the cause.

Other Medications

While antibiotics are not likely to affect your menstrual cycle, other medications can.

For instance, the following medications can cause delays and bleeding changes:

  • nonsteroidal anti-inflammatory drugs (NSAIDs)
  • aspirin and other blood thinners
  • thyroid medications
  • hormone therapy
  • chemotherapy

If you take any of these medications and notice a difference in your menstrual cycle, reach out to your doctor. For some of these medications, that may be a side effect, but for others, it could signify a need for a change in medication or dosing, and a healthcare provider can help you figure this out.


Of course, one of the most obvious reasons for a late period is pregnancy, but this is undoubtedly not the only cause. If you have been sexually active and your period is late, an at-home pregnancy test can help you determine if you are pregnant or, if not, if there is a need to look into other causes of a late period.

Exercising Too Much

There is such a thing as too much of a good thing, which is the case for those exercising too much. By too much, we’re referring to those training for intense sporting events, such as marathons. The large amount of exercise completed in preparation for these events can cause periods to be late.

Polycystic Ovary Syndrome (PCOS)

Those with PCOS have a higher level of androgen and insulin in their body, which can cause periods to be late or missed.

Other symptoms of PCOS include:

  • large ovaries or ovaries with cysts
  • excess body hair
  • acne or oily skin
  • weight gain, especially around the abdomen
  • infertility
  • thinning hair


Menopause is a lifestyle change characterized by changing hormone levels. As you approach this time in your life, it’s normal for periods to become less regular, which may explain why it is late or missed.


Can antibiotics stop your periods?

Antibiotics do not cause a period to stop occurring. If you are sexually active and have not had a period, it is recommended to check for pregnancy using an at-home test or with the help of a physician.

Otherwise, if your periods have stopped, especially if you’re younger than 45, check in with your doctor to get to the bottom of the mystery.

Can antibiotics make your periods early?

We know that antibiotics aren’t likely to be the cause of your late period, but might they be the reason for an early period? The short answer is no.

Early periods often result from hormonal changes, which antibiotics have not been shown to cause. Some more likely causes of an early period include perimenopause, STIs, PCOS, and endometriosis. If you experience an early period, along with other menstrual changes, contact your doctor.

Can antibiotics stop your periods?

Antibiotics do not cause a period to stop occurring. If you are sexually active and have not had a period, it is recommended to check for pregnancy using an at-home test or with the help of a physician.

Otherwise, if your periods have stopped, especially if you’re younger than 45, check in with your doctor to get to the bottom of the mystery.

Can antibiotics delay your period while on birth control?

Similar to a general period, antibiotics are unlikely to delay your period while on birth control. This is because antibiotics have not been shown to alter your hormone levels, so they are unlikely to change anything regarding your birth control, including this efficacy.

Again, the one exception to this is the antibiotic rifampin, which has been shown to alter hormone levels and make birth control less effective.

Still, some doctors think that there may still be a risk of antibiotics interfering with birth control effectiveness, so it’s always best to use an extra form of protection while on an antibiotic, especially if you’re taking rifampin.

Can antibiotics affect your period flow?

Antibiotics will not affect your period flow. However, other medications often taken with antibiotics may. For instance, those who are sick often take aspirin, which is a blood thinner, and this can result in a heavier flow than you would typically experience.

Key Takeaways

Antibiotics are generally prescribed for bacterial infections, and despite the delay in periods that women may experience after taking an antibiotic, this is not usually the cause. Instead, any changes to a menstrual cycle are more likely to result from the illness itself (and the stress it places on your body) or other medications taken to manage symptoms.

Having one late or missed period is not often a cause of concern and is likely related to stress. However, if you’ve missed three periods in a row, your periods have stopped and you’re under 45, or if you think you may be pregnant, it’s recommended to see a doctor.

If you’re ever worried about a late period, an online doctor such as DrHouse can help you quickly discuss your symptoms and devise a treatment plan to help address the problem.


DrHouse articles are written by MDs, NPs, nutritionists and other healthcare professionals. The contents of the DrHouse site are for informational purposes only and are not a substitute for professional medical advice, diagnosis, or treatment. If you are experiencing high fever (>103F/39.4C), shortness of breath, difficulty breathing, chest pain, heart palpitations, abnormal bruising, abnormal bleeding, extreme fatigue, dizziness, new weakness or paralysis, difficulty with speech, confusion, extreme pain in any body part, or inability to remain hydrated or keep down fluids or feel you may have any other life-threatening condition, please go to the emergency department or call 911 immediately.

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