Why You May Faint During Your Period

Table of Contents
View All
Table of Contents

Have you ever fainted or nearly fainted during your period? Wondering if that is normal? Your body undergoes many changes during a normal menstrual cycle. Sometimes these changes can amplify responses in your body that increase your risk of fainting during your period.

causes of fainting during menstruation
Illustration by Brianna Gilmartin, Verywell

Why You Faint

Fainting or passing out, also known as syncope, is your brain's way of communicating to your body that it is not getting the amount of oxygen that it needs. Your brain is very sensitive to oxygen levels and your body has many built-in systems or reflexes to make sure that your brain is getting what it needs.

Sometimes changes in your body trigger these reflexes and as a result, you pass out. This is exactly what happens in the most common type of fainting called neurocardiogenic or vasovagal syncope.

Vasovagal syncope is caused by an altered response to certain situations by the part of your nervous system that automatically controls many vital body functions. We don't know exactly how it happens but reflexes are triggered causing changes in your heart rate and blood pressure that result in decreased blood flow to your brain.

As these changes are happening they cause typical symptoms that are known as pre-syncopal symptoms including:

  • Nausea
  • Sweating
  • Lightheadedness
  • Blurred vision
  • Heart palpitations or rapid heartbeat
  • Paresthesia or sensation of numbness
  • Pallor or looking pale

In a way, these symptoms are a warning sign for you to try and change what you are doing. Often a syncopal episode can be avoided as you change what you are doing because you're not feeling well. But sometimes, these symptoms come on too fast and you can't prevent yourself from fainting.

The changes in your body that can trigger neurocardiogenic or vasovagal syncope are amplified during your period. In other words, some of the changes that happen in your body each month during your period can increase your chance of fainting or almost fainting.

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 reflexive changes in your body that cause you to faint. But there might be something else about your period pain that increases your chance of fainting.

Primary dysmenorrhea or a painful period with no underlying cause is related to prostaglandin production. Prostaglandins are produced in the endometrium or the lining of your uterus in the late luteal phase or second half of your cycle right before and just as your period starts.

If you have very painful periods it is thought that your prostaglandin production may be increased. Prostaglandins are involved in many key functions in your body related to handling illness and injuries. One of these functions is causing your blood vessels to dilate, a process known as vasodilation.

One of the reflex changes that can lead to vasovagal syncope is vasodilation. It is thought that perhaps the increase in prostaglandins results in more significant vasodilation, which in turn drops your blood pressure. This sets the stage for an exaggerated response and an increased chance of fainting due to the pain caused by menstrual cramps.

Taking a medication called a nonsteroidal anti-inflammatory drug or an NSAID like ibuprofen to decrease prostaglandin production is probably your best treatment option. This will ease your pain and may block the vasodilatory effects of excess prostaglandins in your system.

Heavy Periods

Often, a heavier menstrual flow is associated with more of a build-up of the endometrial lining of your uterus during your menstrual cycle. As noted above, the more endometrial tissue the greater the prostaglandin production. Prostaglandins are thought to increase one of the changes that can lead to vasovagal syncope.

In addition to prostaglandins, heavy periods can lead to chronic blood loss which causes anemia. When you are anemic, you are ultimately reducing the amount of oxygen that your blood can carry around your body. When your brain senses even the slightest decrease in oxygen it triggers the reflexive changes that can lead to vasovagal syncope.

Eating foods rich in iron or taking iron supplements to help increase the oxygen-carrying capacity of your red blood cells may help you to avoid this cause of fainting during your period.

Hormonal Changes

Fluctuating hormone levels are the basis of your menstrual cycle. If you are having regular ovulatory cycles, the concentration of estrogen and progesterone in your body differs in the first half of your cycle, mid-cycle, and in the second half of your cycle. During the start of your period, both the amount of estrogen and progesterone in your body are at their lowest levels.


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 of hypoglycemia can happen even if you do not have diabetes. Hypoglycemia is another change in your body that can trigger the reflexive changes that cause vasovagal syncope.

Eating breakfast, eating small frequent meals throughout the day, and limiting foods high in simple sugars can help to minimize episodes of hypoglycemia.

Fluid Shifts

It is also thought that the low hormonal levels during menstruation may cause exaggerated body fluid shifts in some women as the fluid in the bloodstream moves into body tissues. This results in edema or swelling especially of the legs and ankles and less fluid in the blood vessels.

Your body reacts to this much as it does to dehydration. Because the volume of fluid in your bloodstream is less your body can't adjust to position changes as well so your blood pressure drops. This is called orthostatic hypotension and this drop in blood pressure can then trigger the changes that can cause you to faint.


These hormonally induced fluid shifts can also aggravate a specific condition in young women called postural orthostatic tachycardia syndrome (POTS). This disorder disrupts the part of your nervous system that automatically controls many vital body functions like your heart rate and blood pressure.

Women with POTS experience fatigue, dizziness, and frequent fainting which often increase during menstruation.

Making sure you stay well hydrated by drinking lots of water, avoiding getting overheated, and avoiding prolonged standing will help to decrease your chances of fainting during your period. If you do feel faint, lay down with your leg raised, or sit down.

A Word From Verywell

If you are susceptible to fainting 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 as it could be a sign of a more serious problem.

Was this page helpful?
Article 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.
  1. Grossman SA, Badireddy M. Syncope. In: StatPearls. Updated December 16, 2019.

  2. Jeanmonod R, Silberman M. Vasovagal episode. In: StatPearls. Updated February 5, 2020.

  3. Muppa P, Sheldon RS, McRae M, et al. Gynecological and menstrual disorders in women with vasovagal syncopeClin Auton Res. 2013;23(3):117–122. doi:10.1007/s10286-013-0190-1

  4. Mechanic OJ, Grossman SA. Syncope and related paroxysmal spells. In: StatPearls. Updated December 27, 2019.

  5. Sawai A, Tochigi Y, Kavaliova N, et al. MRI reveals menstrually-related muscle edema that negatively affects athletic agility in young women. PLoS ONE. 2018;13(1):e0191022. doi:10.1371/journal.pone.0191022

  6. Fu Q, VanGundy TB, Shibata S, Auchus RJ, Williams GH, Levine BD. Menstrual cycle affects renal-adrenal and hemodynamic responses during prolonged standing in the postural orthostatic tachycardia syndrome. Hypertension. 2010;56(1):82–90. doi:10.1161/HYPERTENSIONAHA.110.151787

  7. Nwazue VC, Raj SR. Confounders of vasovagal syncope: postural tachycardia syndromeCardiol Clin. 2013;31(1):101–109. doi:10.1016/j.ccl.2012.09.004