What is

heavy menstrual bleeding?

What is

heavy menstrual bleeding?

In order to understand what heavy menstrual bleeding (HMB) is, it helps to understand what a normal period is. Getting to know your cycle will help when it comes time to talk to your doctor.

Woman reading poster with uterus, pad, and tampon on it

Let's start at the beginning:

Just what is a “normal” period, anyway?

Everyone is different, which can make it hard to know what “normal” even means. But there is an average, or range of typical characteristics. For example, a “normal” period (or menstrual flow) may:

Calendar with star for period starting every 28 days

Occur every 28 days on average

Box showing 4 to 5 days of a normal menstrual cycle

Last for
4 to 5 days

Test tube filled with 35 to 40 milliliters of blood reflecting a normal period blood loss

Result in a total blood loss of 35 mL to 40 mL

A normal period

may result in a blood loss of 35 mL to 40 mL (2 to 3 tablespoons)

Graduated beaker filled with 35 to 40 milliliters of blood

a heavy period,

which may result in a blood loss of 80 mL (5 to 6 tablespoons) or more.

Graduated beaker filled with 80 milliliters of blood

What is a “heavy” period, exactly?

According to the objective standard for measuring HMB, women with HMB may lose 80 mL of blood (5 to 6 tablespoons) or more during their period and may have bleeding that lasts longer than 7 days.


While common, HMB is not a normal or typical event. It can interfere with your work life, social plans, or daily activities. 

Your period may be heavy if you:

  • Soak through 1 or more pads or tampons every hour for several hours in a row
  • Need to wear more than 1 pad at a time to control your bleeding
  • Need to change pads or tampons during the night
  • Have periods with blood clots that are the size of a quarter or larger
  • Have periods that last more than 7 days
  • Have a heavy flow that keeps you from doing the things that you would normally do
  • Have constant pain in the lower part of the stomach during your period
  • Feel tired, lack energy, or experience shortness of breath 

Talk to your doctor to learn more and see if you may have heavy menstrual bleeding.


In order to understand what you are experiencing, your doctor may run some tests, including: 

Blood test results sheet

A blood test to check for anemia, thyroid problems, or blood clotting issues

Beakers and test tube for Pap test

A Pap test to determine if you have an infection, inflammation, or
cell changes

Microscope examining endometrial tissue from uterine lining

An endometrial biopsy to examine tissue from the lining of your uterus 

Ultrasound equipment for examining your reproductive organs

An ultrasound to see how your blood vessels, tissues, and reproductive organs are working

Why do some women experience heavy periods?

Heavy periods are one of the most common problems that women share with their doctors. Several conditions may cause heavy periods, or HMB; however, there are many times in which heavy bleeding does not have a known cause.

Some of the possible causes include:

  • Uterine-related problems
  • Hormone-related problems
  • Other illnesses or disorders
Smiling, red-headed woman who might be a candidate for hormonal treatment

Some women who have heavy periods have no evidence of any physical abnormality and their doctors are unable to find the cause. If there is no gynecological problem, and other causes are ruled out, you may be a candidate for hormonal treatment. Talk to your doctor to see what treatment options are available.