Can the Covid Vaccine Affect Your Period?

If you are a menstruator and have received the COVID vaccine please consider participating in this study to help further research on this topic.

Over the last year we've heard from thousands of menstruators about what they've been experiencing in regards to COVID-19 and the affects they've seen the virus have on their menstrual cycles.

Last week we started to hear from menstruators discussing changes they were noticing to their periods after receiving the COVID-19 vaccine.


Katherine Lee, a post-doctoral scholar in the public health sciences division at the University of Washington School of Medicine, was one of those women noticing changes and reached out to her grad school professor, Kathryn Clancy, head of the Clancy Lab at the University of Illinois.

Clancy was interested in the topic and then she received her first dose of the Moderna vaccine. "A little after a week after this first Moderena dose and I had never had a period that was so heavy - not even in my 20s when I was having a really heavy cycle," Clancy Said.

<< Want to participate in a study to further the research on this topic? Participate here. >>

As noticed with how the menstrual cycle responds to COVID-19, the menstrual cycle responds to stress, physical or mental, including immune responses or changes. So it's really no surprise that people are noticing changes to their cycles. The important thing to notice is that this is a side effect and it should be taken into account so that people can be properly prepared for them.

Clancy and Lee noticed a large response to their questions around menstruation and the COVID vaccine on twitter and organized a study to gather more research.


 It is important to note that both researchers are pro-vaccine and are conducting the research in order to understand all of the side effects.

The History of Vaccines & Menstruation

It wasn't until the 1990s that the National Institutes of Health recommended (not even required!) balanced recruitment for drug trails. That means that it's not necessary to study the side effects on men vs women. Historically lots of biological and cultural differences have not been taken into account when researching new drugs or vaccines.

How the COVID-19 vaccine impacts the female reproductive system continues to remain unknown for now. However, researchers do have some understanding of how the infection of COVID-19 impacts menstruation due to a few key studies.

A study of 200 women in China found that 25% had some kind of changes in their cycles. Both symptoms of blood volume and timing irregularities were present. There has been assumptions made that inflammation is playing a roll in these side effects.

In addition, Dr. Gloria Bachmann, OB-GYN and director of Women's Health Institute at the Rutgers Robert Wood Johnson Medical School, has noted that estrogen is also involved with COVID-19.

"Estrogen does (have an) impact on COVIS so that there is sort of a connection. It's not a bad connection but it may be a connection that alters a period."

This makes complete sense to us knowing that estrogen plays a role in heavy periods, early period, skipped periods and other irregularities.

Experiencing Irregularities?

If you are experiencing irregularities it is best to communicate with your doctor. Be sure to keep thorough details on the irregularities and provide as much information as possible. You can also report these irregularities to V-Safe to help the CDC monitor side effects of the COVID-19 vaccine.

If you're interested in participating in Dr. Clancy's study please do so here.




Spike protein jn vaccine is effecting platelets. Women with lower platelet count to begin with will experience heavier bleeding and will exacerbate symptoms of ITP. If you take aspirin or ibuprofen for pain it will also reduce the platelet count causing more bleeding. Avoid all blood thinners including aspirin and ibuprofen and most anti inflammatories if you have the vaccine and low platelets as a precaution. Consider consulting with a hematologist if you are experiencing an increase in bleeding and monitor your platelet , ferritin, and iron levels

Kendra September 06, 2021

My experience was similar to Heather’s (May 2021). After having the virus my period was late then terribly heavy and about 2 weeks long. No one has mentioned this – about a month after recovering from COVID, my hair began to come out in handfuls! That continued for weeks until I ended up with much thinner locks then I had before. This too is a hormonal issue like our menstrual cycle and I believe is related to this after effect of this rotten virus. I would have been so confused about the hair loss unless a friend has shared her experience with me. Maybe this will relieve someone of any fear or anxiety over this effect. Blessings everyone!

Katy August 07, 2021

I was around someone who had recently been vaccinated and shortly after my period started. It was so heavy I had to go to the ER on day 2 because I was passing out. Large clots too.

Rita August 07, 2021

I thought it was pretty weird considering the older I’ve gotten the less heavy my flow was getting. I’m 28, 115 pounds, 5’1, but however when I got the vaccine I got my period 3 days later and never have I gotten so much blood clots it felt like i had blood clots for 3 days straight and they weren’t tiny either and filling up a tampon in an hour. It was scary but the only think I had changed that month was getting the shot. But my flow went from mild to extreme heavy duty.

Arie May 03, 2021

I am a male but i think it’s important to share this information with the females i know in my life, family, friends, colleagues. Thank you!

Juan Herrera May 03, 2021

Hi! I’m new here and would like to know what your opinion is (or what have you read) about the Covid vaccine being able to get you sterile. Thank you

Belen May 03, 2021

I had the vaccine in January and also had a baby last March but the first two periods I had were heavy but I didn’t have any cramps and I still don’t experience any cramping and I’ve had 5 cycles.

Ericka May 03, 2021


Since I have gotten my second vaccine on 2-11-21 Moderna vaccine my period hasn’t stopped. I went to Mount Sinai gyno ER to have that checked and they have found a fibriod 4.3cm. Since the vaccine I feel a lot heavier my stomach is popping out like I am pregnant. I am going for an MRI today and seeing other health services that can help to remove the fibriod. The bleeding has stopped still and it has been more than 2 months. I had made a complain on CDC about this but no feedback. I am anemic and feeling more tired and warned out day by day.

Kamrunnahar Kanny May 03, 2021

I experienced irregular cycles after the vaccine shot, before vaccine I was very regular! One month I had 2 periods second month I was a week late….

Rose May 03, 2021

Would love to be a part of the vaccine research about how it affects the menstrual cycle! I am (hopefully) nearing the end of an over month long cycle! I have the nexplanon and haven’t had a solid period in over a year, just the occasional spotting and this current cycle after receiving the vaccine has been a month long blood bath to say the least and I’m not in the clear yet

Katelyn May 03, 2021

I am on a medication called Orilissa for my severe endometriosis pain. it’s a pill that dials down estrogen. Lower estrogen levels can help manage endometriosis pain. Ever since my first dose of moderna I have been in constant pain with no relief in sight. I also didn’t get my period this month. Seeing a doctor this week about it, but I’m afraid that my first shot is somehow interfering with my medication and I have been absolutely miserable.

Jacqulyne Morici May 03, 2021

My periods are heavy regardless lol. And to be honest I can’t really tell if my periods are heavier after the shot! In fact I think they are slightly lighter but not by much!! lol It could be because of my IUD. Heavier bleeding probably occurs to some women but not all I’m sure. I don’t feel or see anything different 🤔

Bethany C. May 03, 2021

I didn’t receive the vaccine, but I did have Covid and from the little I read I had a very similar experience. Being someone who takes birth control I can usually predict my periods flow and date of arrival. After having covid for 3 weeks my first period was 2 days late and gushing. I mean a tampon and a pad together gushing. I had to change my feminine products once or twice every hour for 2 days. This is very unlike me from being late to the flow. Not only was this my experience, but I’ve spoken to a few women who had covid and are waiting to get the vaccine. It was a similar or very similar situation. I think you guys are on to something!!

Heather May 03, 2021

I usually get mine every other month, it kinda just comes there’s no consistency but after I got my covid vaccine I now get it every month

Breann May 03, 2021

Although I got my period early I didn’t notice a heavier bleed. I did, instead noticed lighter period flow and no cramping at all. One of the best periods I’ve experienced in a long time.

Shavon May 03, 2021


I was diagnosed with COVID on September 1st after battling this nasty virus for 15 days I lost my menstrual cycle for 3 months. I followed up with my OBGYN and she stated that when the body is affected by a severe virus often times the body will stop menstruating to protect itself. Upon return of my period I was in severe pain, bleeding extremely heavy and passing a significant amount of blood clots. My periods have never been these bad, I was in so much pain & bleeding so heavy I thought something was wrong with me. Since COVID this is my new normal which has been extremely difficult to manage for 7 days. I also find a week prior to my cycle I feel as if I am experience the same symptoms I did with covid, fatigue, body aches etc. I have complete my 2nd dose of Moderna 2 weeks ago and am patiently awaiting a positive change hoping the vaccine does not make my cycle worse. I feel for everyone out there experiencing this and would love to know more about why this is occurring!

Jessica May 03, 2021

I finished my period one week before my 1st Asta zeneca vaccination and I started spotting 2 days later its been a week and I’m still spotting

Lisa May 03, 2021

I took the Pfizer vaccine and after the second dose I got my period. I’m an ITP patient (low platelets) so I am quite used to having heavier periods but after the vaccine, my period was considerably a lot heavier, with more pain than usual. I was unable to work for three days after, not because of the usual spoke about vaccine side effects but because my period was interfering with my daily life. My period also lasted 9 days, when usually it only lasts about 6.

Shayna Patel May 03, 2021

After receiving my 2nd dose of the Covid vaccine I had my cycle on time but the bleeding was so horrible, I had tons of clots, my bp got up to 155/105 and I had to be admitted to the hospital! I’ve never in my life had a heavy period. Now I’m 10 days late with my next cycle after that happened….

Danielle May 03, 2021

Hello i wasnt to sure why but maybe this is it. Ive had my covid vac and my period was 2 weeks late usually like clock work.

Jennifer Loboda May 03, 2021

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