Why You May Faint During Your Period

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Have you ever fainted or nearly fainted during your period? If so, you may wonder if that's a common experience. You may also be concerned that it's the sign of a serious issue.

Your body undergoes many changes during a normal menstrual cycle. Sometimes these changes can heighten certain responses in your body that increase your risk of fainting during your period.

First, this article will explain the medical reasons for why people faint from any cause. It then explains the specific reasons for why that may happen during your period and what you can do about it.

causes of fainting during menstruation

Verywell / Brianna Gilmartin

Why You Faint

The medical term for fainting or passing out is called syncope. It is your brain's way of telling your body that it is not getting the amount of oxygen that it needs. The brain is very sensitive to oxygen levels, and your body systems work to ensure it gets the oxygen it needs.

Sometimes, a certain reflex may cause you to pass out. This is exactly what happens during vasovagal syncope, the most common type of fainting.

Vasovagal syncope involves both your nervous and cardiac systems. The nervous system is always sending signals that control heart rate and other vital functions in your body. One of those nerves is the vagus.

Certain things can trigger a reflex in which the vagus nerve sends signals that cause heart rate and blood pressure to drop quickly. This can cause decreased blood flow to your brain.

As these changes are happening, they cause common symptoms that may include:

  • Nausea
  • Sweating
  • Lightheadedness
  • Blurred vision
  • Rapid or irregular heartbeat
  • A sense of numbness (paresthesia)
  • Pallor, or looking pale

If you know the warning signs, you can try to avoid fainting because of a vasovagal response. But sometimes, these symptoms come on too fast and you can't stop yourself from fainting.

During your period, some of the changes in your body that may trigger a vagal episode are amplified. This may increase your chance of fainting or nearly fainting.


The most common type of fainting is called vasovagal syncope. Certain triggers can cause heart rate and blood pressure to drop. This reduces the amount of oxygen that reaches the brain and may lead to a fainting episode.

Painful Periods

Pain, in general, is a known trigger for vasovagal syncope. Just like other forms of pain, your response to period pain can cause the changes in your body that lead you to faint. But there might be something specific about period pain that increases your chance of fainting.

Primary dysmenorrhea, or a painful period with no underlying cause, is related to a hormone called prostaglandin. The body produces this hormone in the endometrium, the lining of your uterus. It does so during the later part of your menstrual cycle, right before and just as your period starts.

Painful periods may cause your body to make more prostaglandin. The hormone is involved in key responses in your body needed to manage pain, illness, and injury. One of these responses will cause your blood vessels to open wider, a process known as vasodilation. This is a healthy response in some situations, like when you exercise, but it also may be the cause of your fainting.

That's because your blood pressure can drop when your blood vessels are wider. This may set the stage for a heightened vagal response, and a higher risk of fainting due to the pain caused by menstrual cramps.

Taking a nonsteroidal anti-inflammatory drug (NSAID) like ibuprofen is probably your best treatment option. This will both ease your pain and decrease prostaglandin production. This, in turn, may decrease your risk of fainting.

Heavy Periods

Often, a heavier menstrual flow is associated with more build-up of the endometrial lining in your uterus during your menstrual cycle. This may lead to more prostaglandin production—which, as noted above, might also increase the chances of a fainting episode.

Heavy periods also can lead to blood loss that causes anemia. When you are anemic, the amount of oxygen that your blood can carry is lower. When your brain senses even the slightest drop in oxygen levels, it triggers the changes that may lead to fainting.

Eating foods rich in iron or taking iron supplements may increase the amount of oxygen your blood can carry. It may help you to avoid this cause of fainting during your period.

Hormonal Changes

Changes in hormone levels are the basis of your menstrual cycle. If you have regular cycles, the estrogen and progesterone levels in your body change in typical ways across the cycle. During the start of your period, these hormone levels are at their lowest.


In some women, these hormonal shifts can cause changes in insulin sensitivity that can lead to episodes of relatively low blood sugar called hypoglycemia. These episodes can happen even if you do not have diabetes. Low blood sugar levels also may lead to a vasovagal response that causes you to faint.

Simple shifts in diet can help you to avoid low blood sugars that may lead to fainting during your period. Be sure to have breakfast, and eat smaller meals more often throughout the day. Avoiding foods high in simple sugars, like candy, can help to minimize any episodes of hypoglycemia.

Fluid Shifts

Another possibility for why you have fainting episodes is linked to fluid shifts in your body. The low hormonal levels during a period may cause more fluid to move from the bloodstream and into body tissues. This may cause edema, or swelling, of the legs and ankles. It also means less blood volume.

Your body reacts to this much as it does to dehydration. Because the amount of fluid in your bloodstream is less, your body can't adjust as well to changes in position. This may cause a drop in blood pressure when you stand or move, called orthostatic hypotension, which can lead to fainting.


Fluid shifts caused by hormone changes can also aggravate a specific condition in young women called postural orthostatic tachycardia syndrome (POTS). This disorder disrupts the nervous system's normal ability to control heart rate and blood pressure.

Women with POTS experience fatigue, dizziness, and frequent fainting. These symptoms will often increase during your period.

Make sure that you stay well hydrated by drinking lots of water. Try not to get overheated, and avoid standing for long periods of time. This will help to decrease your chances of fainting during your period. If you do feel faint, lie down with your legs raised, or sit down.


Some women do experience fainting spells during their periods. In many cases, hormonal changes in the body during your period may be part of the reason. These can lead to lower blood pressure, less blood volume, lower blood sugar, anemia, and a more sensitive vagal response.

All of these can lead to fainting. In most cases, though, these episodes are not caused by a serious medical condition. Simple diet and lifestyle changes, along with taking the right pain medication, can often prevent fainting.

A Word From Verywell

If you are prone to fainting episodes during your period, making small changes to your routine can help to reduce the risk. But, it is important that you discuss fainting during your period with your healthcare provider.

7 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Andrea Chisholm, MD
Andrea Chisolm, MD, is a board-certified OB/GYN who has taught at both Tufts University School of Medicine and Harvard Medical School.