Recent research shows that the COVID-19 vaccine can cause menstrual irregularities and postmenopausal bleeding. These symptoms typically resolve on their own within a few weeks.

There have been discussions lately on internet forums and social media about how the COVID-19 vaccine affects menstruation.

Recent research suggests the COVID-19 vaccine can cause menstrual irregularities. But these irregularities typically only occur in the weeks immediately after vaccination.

The COVID-19 vaccine may also be connected to postmenopausal bleeding.

Menopause happens when you’ve gone 1 year without a menstrual period. During the years leading up to menopause, known as perimenopause, many people experience irregular menstrual cycles.

If you’re wondering whether the menstrual changes you’re experiencing are from perimenopause, the COVID-19 vaccine, or something else, here’s what you need to know.

Menstrual cycles can differ significantly from person to person. They can change across a person’s lifetime too. This is especially true during perimenopause, when inconsistent cycles are the norm.

People have reported various menstrual irregularities (and postmenopausal changes) after receiving their COVID-19 vaccines. Some of these reports are anecdotal, but others are backed up by research.

In the United Kingdom, 30,000 reports of menstrual irregularities and postmenopausal bleeding were sent to the Yellow Card adverse events reporting site before September 2021.

These numbers are actually quite low when compared with the number of people vaccinated against COVID-19 and the standard presence of menstrual irregularities.

Most people who report menstrual changes after being vaccinated against COVID-19 returned to their regular cycle within 2 months — though in some cases, reported changes were more long lasting.

In large surveys of vaccinated people, all types of COVID-19 vaccines appeared to contribute to menstrual abnormalities.

Did you know?

The average menstrual cycle (counting from the first day of your period to the first day of your next period) lasts 24 to 38 days.

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Researchers have found a small increase in menstrual cycle length after COVID-19 vaccination for some people, about 1 to 2 days on average. This means your period may be late.

Since those numbers are averages, that means some people are waiting even longer for their period to show up.

The same researchers found that people who received both doses of a two-dose COVID-19 vaccine within the same menstrual cycle experienced the greatest number of changes in their cycles and the largest increase in cycle length.

These changes were temporary and did not appear to increase the number of bleeding days in people’s cycles, but lengthened overall cycle length.

Theories suggest that immune reactions affecting reproductive hormones could cause changes in menstruation.

Less research has included people in perimenopause. One reason is that major menstrual changes are very common in perimenopause due to fluctuating hormone levels. These changes occur regardless of vaccination status.

Perimenopause typically lasts several years, even a decade. If it’s been 12 or more months since your last period, you’re no longer in perimenopause. You’ve reached menopause.

It’s common for people to experience the following symptoms during perimenopause:

  • chills
  • hot flashes
  • loss of breast fullness
  • mood changes
  • night sweats
  • period irregularity
  • sleeping issues
  • slowed metabolism
  • thinning hair and dry skin
  • weight gain

In one 2021 study, researchers observed a possible increased risk of blood clots after vaccination with the Oxford-AstraZeneca COVID-19 vaccine in perimenopausal women taking hormonal birth control.

Other brands of COVID-19 vaccines have not shown the same risks.

There have been some reports of vaginal bleeding in postmenopausal women following COVID-19 vaccination.

Several case reports have shown vaginal bleeding in women whose last period was around a decade ago. Postmenopausal bleeding, especially when it’s been years since menopause started, isn’t usually serious but is a cause for concern.

If you experience postmenopausal vaginal bleeding, talk with a doctor about the potential causes.

People who take estrogen-containing medications appear to have an increased risk of blood clots if they get the AstraZeneca COVID-19 vaccine. The AstraZeneca vaccine is not approved for use in the United States. Other vaccines approved by the Food and Drug Administration (FDA) have not had the same effects.

How to report unusual vaccine symptoms

If you experience unusual menstrual or menopausal symptoms after COVID-19 vaccination, you can report your symptoms to the Vaccine Adverse Event Reporting System (VAERS). VAERS is co-managed by the FDA and Centers for Disease Control and Prevention (CDC).

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Menstrual problems are common. Any number of things can cause them, such as:

Lastly, there’s some evidence that viral infections, including COVID-19, may alter the menstrual cycle. Scientists believe such changes could happen because of an immune response that affects hormones.

Menstrual and menopausal changes are fairly common. COVID-19 vaccines might trigger an immune response that can cause slight changes in menstrual cycle length.

There have also been reports of postmenopausal bleeding.

These changes appear to be temporary, resolving within a matter of weeks. The benefits of COVID-19 vaccination far outweigh the risk of short-term menstrual changes.