Flash Flood: Why is My Period Suddenly Heavier than Normal?

This article was medically fact-checked by Women’s health expert and Gynaecologist Dr. Alyssa Dweck.

We like to think that, no matter how light and short or long and disastrously heavy our periods are, they at least follow a familiar pattern. It can be quite disconcerting then, when our previously steady cycles deviate significantly from the norm. To put your mind at ease, here are the basics of heavy bleeding, including when it is and isn’t a big deal.

First, What Constitutes ‘Heavy’?

The average period will see about 30 mL ( 1 fluid oz ) of blood loss with a normal upper limit of 80 mL (2.7 fluid oz). If you’re using a Lily Cup Classic A, for example, you’d probably fill it completely less than 3 times over the course of your period. Menstrual cups make it very easy to monitor the amount of flow you have but ‘heavy’ can also be indicated by:

  • Needing to change your pad or tampon at least every 1-2 hours
  • Needing to change your pad in the middle or the night or double up
  • Pass blood clots larger than an American quarter

Heavy periods are more common when hormone levels may fluctuate such as in our teens or right before menopause, or, again, always be heavy throughout your life. It’s called menorrhagia, and if it’s a sudden shift (or you are anemic) this is something to discuss with your doctor.

Main Causes Of Menorrhagia

1. You Just Switched Up Your Birth Control

If you’ve just switched to the mini-pills (the ones that are progestogen-only as opposed to combination pill containing estrogen and progesterone) or are coming off oral contraceptives entirely, chances are you will notice a heavier flow. The patch is also associated with lighter periods, so discontinuing use of it may cause your flow to get heavier. 

In general, when discontinuing hormonal contraception, your period habits will likely revert to what they were prior to initiating. 

When it comes to IUDs, while the hormonal varieties such as Mirena tm, Kyleena tm and Liletta tm are associated with lighter periods, the non-hormonal copper IUD Paraguard tm, may actually cause heavier bleeding in many women.

2. You’re Peri Menopausal

Yep, this wondrous 4-8 year transition leading up to menopause—known as perimenopause—can affect women as young as 30, so don’t rule it out as the cause of suddenly heavier bleeding, especially if there is a history of early menopause in your family.

3. You’re Taking Blood Thinners

Have you ever gone to get your ear pierced and forgotten to mention to the piercer that you took some Advil for pain? You (and your poor piercer) probably encountered a LOT more blood than they were banking on.

It doesn’t always click—and we aren’t always warned—of all the ways that new medication will impact our bodies, so you may have not realized that anticoagulants such as coumadin will indeed cause a heavier period than normal.

Anticoagulants and other anti-inflammatories prevent clots so that blood can flow more easily through your body… which includes, you guessed it—your period.

4. You Have Uterine Fibroids

While it might sound serious, uterine fibroids are actually benign and super common muscular growths usually found in the uterus. In some cases, fibroids can cause unpleasant menstrual side effects—painful cramping and heavier flow.  In other cases, they are unnoticeable.

5. You Have Polycystic Ovary Syndrome (PCOS)

Affecting between 8-20% of women worldwide, PCOS is a condition in which ovulation occurs infrequently, irregularly or not at all resulting in hormonal imbalance, thick uterine lining tissue and you guessed it, wonky periods.  Menses might be absent for months at a time, irregular, heavy and lengthy when they do come. 

6. You Have An Infection

Any infection of the uterus can cause heavier bleeding—yes, this includes STIs like gonorrhea and chlamydia. These types of infection cause pelvic inflammatory disease, which can lead to infertility. If you have had unprotected sex—penetrative or oral—and notice heavier bleeding and pelvic pain  it’s important to get yourself tested and treated if need be.

Facts checked by:

Dr. Alyssa Dweck

Dr. Alyssa Dweck

Alyssa Dweck MS, MD, FACOG is a practicing gynecologist in Westchester County, New York. She provides care to women of all ages; she has delivered thousands of babies. She is proficient in minimally invasive surgery and has special interest and expertise in female sexual health and medical sex therapy. She is top doctor in New York Magazine and Westchester Magazine. Dr. Dweck has co-authored three books including the most recent release The Complete A to Z For Your V.

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