Most people lose around 2–3 tablespoons of blood during their period. People with heavy periods may lose twice as much. Fatigue or weakness may be signs that a person is losing too much blood.

This figure comes from the Centers for Disease Control and Prevention (CDC).

Menorrhagia is the medical term for heavy menstrual bleeding. A person has heavy periods if they need to change their pad or tampon less than every 2 hours, or if they pass clots the size of a quarter or bigger.

Heavy periods can be a sign of an underlying health issue. Sometimes, a person may mistake an early miscarriage for a heavy period. Sudden, very heavy bleeding may be a medical emergency.

Read on to learn about signs you are losing too much blood during a period.

A woman lying on a sofa with cramps due to a period.Share on Pinterest
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A typical period causes around 2–3 tablespoons (tbsps) of blood loss. However, this may vary from person to person. A person with heavy periods may have twice as much blood loss, while others may have less.

It can be difficult to measure the precise volume of blood loss at home. Using a menstrual cup can help to measure the blood loss, which may help a person give their doctor more precise information.

Another way to quantify blood loss is to examine how often a person changes their pad or tampon. A person is losing too much blood during their period if they:

  • soak through a pad or tampon once an hour for several hours
  • pass large clots the size of a quarter or bigger
  • have to use two pads at a time to prevent leaks
  • have to change pads or tampons during sleeping hours

People can have heavy periods without experiencing any additional symptoms. However, sometimes the blood loss can contribute to anemia. This may cause:

  • shortness of breath
  • low energy
  • weakness

A person does not have to have these symptoms to get help from a doctor. Heavy bleeding alone may indicate that there is an underlying condition.

Heavy periods are not usually an emergency. However, people can mistake other conditions for a heavy period. These other conditions can require urgent treatment.

For example, postpartum hemorrhage can occur up to 12 weeks after giving birth. Injuries to the uterus and bleeding disorders can also cause dangerous bleeding that requires emergency treatment.

Additionally, an ectopic pregnancy or miscarriage can mimic a heavy period, and may be mistaken for one if a person does not know they were pregnant. An ectopic pregnancy occurs when the pregnancy begins outside the uterus, usually in the fallopian tube.

If a person starts losing a lot of blood from the vagina, or has the following symptoms, call 911:

  • pale or clammy skin
  • rapid heart rate
  • nausea
  • dizziness
  • blurry vision
  • fainting
  • swelling around the vagina, or in the space between the vagina and anus (perineum)

If a person often has periods that soak through tampons and pads within a few hours or less, or that consist of large clots, they should also speak with a doctor.

Some potential causes of heavy periods include:

As many as 20% of people with unusually heavy periods have a bleeding disorder, or coagulopathy.

Frequent nose bleeds, bleeding gums, bruising, or significant bleeding from minor cuts may indicate a person has coagulopathy.

Doctors may be able to diagnose heavy periods by asking about a person’s symptoms. If they regularly experience heavier blood loss than is typical, or that the blood loss causes symptoms of anemia, they may give a diagnosis of menorrhagia.

The doctor should also perform tests to check for the potential causes, or complications of, having heavy periods. This may include a:

A doctor may also recommend scanning the uterus and ovaries to assess the cause. This may show signs of growths or lesions.

If they the suspect the growths result from polyps or cancer, they may perform a biopsy to test the uterine tissue.

Treatment for heavy vaginal bleeding will depend on the severity of the blood loss, and on what is causing it.

Severe bleeding

If the bleeding is severe, the first goal for doctors may be to reduce the bleeding. To do this, they may fit an IV line, give a blood transfusion, or apply pressure inside the uterus using a Bakri balloon or gauze.

Another way doctors can reduce bleeding is to ensure the bladder is empty and is not in the way of the uterus contracting. They can empty the bladder with a Foley catheter.

Doctors will then examine the cause of the bleed to determine further treatment. For example, they can remove remaining products in the uterus during surgery. They may administer IV drugs to stop bleeding.

In some cases, a doctor may administer short-term hormone therapy to stop the bleeding. They may also give hormonal contraceptives to take home, as this may prevent bleeding from recurring.

If these measures do not work, surgery may be necessary. Dilation and curettage removes the top layer of the uterine lining, which can quickly stop bleeding.

Pregnancy-related conditions

If the bleeding is the result of a pregnancy-related complication, treatment may involve:

  • Monitoring: If doctors identify an ectopic pregnancy early, they may monitor it to see if treatment is necessary. Ectopic pregnancies are not viable, and sometimes, the pregnancy will end on its own.
  • Medication: Postpartum hemorrhage usually requires medication, such as pitocin or methergine, to stop the bleeding. If the bleeding is severe, a person may need a blood transfusion, or IV estrogen. A hysterectomy may also be necessary in life threatening circumstances.
  • Surgery: A miscarriage or more advanced ectopic pregnancy may require surgery to remove the pregnancy.

Other conditions

If the bleeding is unrelated to pregnancy, treatment focuses on identifying and managing the underlying cause, and reducing the symptoms. This may involve:

  • IUD removal
  • hormonal contraceptives
  • hormone replacement therapy, for heavy bleeding due to perimenopause
  • medications to treat thyroid or liver disorders
  • medications for bleedings disorders
  • antibiotics for PID
  • surgically removing fibroids or polyps
  • eating more iron-rich foods, or taking a supplement

Other surgeries, including uterine artery ablation and hysterectomy, may stop heavy periods if other options do not work. It is important to discuss the risks and benefits of these treatments with a doctor.

If a person experiences tiredness, weakness, or shortness of breath while on their period, it can be a sign they are losing too much blood.

According to the CDC, most people lose around 2–3 tbsps of blood during a period. Heavy periods may cause twice as much blood loss.

If blood often soaks through tampons or pads in less than 2 hours, or a person often passes large clots, they should speak with a doctor. Heavy periods is not something a person has to tolerate, and it may signal an underlying medical condition that needs treatment.