Nov 19 2009

Menstrual Blood Problems

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What is normal?

Women will often look at the color and texture of their menstrual blood. Seeing difference from the start to the end of your flow, or seeing a difference from month to month is perfectly normal. There are however also times when a change in color, clotting or consistency may indicate deeper problems.

Even though you might find it embarrassing to talk to your medical care provider about something as embarrassing as your menstrual blood, it is important to talk to him or her about concerns you might have.

During your normal monthly cycle, the lining of your uterus (endometrial) thickens to get ready for implantation of a fertilized egg and possibly pregnancy. If your egg does not get fertilized, your uterus sheds the uterus lining along with blood during menstruation (your period),. The amount of blood and fluid lost is around 35 ml with an amount between 10 ml to 80 ml (3 and 15 teaspoons) each cycle considered normal.

The average menstrual cycle is 28 days long but is can last from as little as 21 days up to 35 days without cause for concern. Menstruation (your period) lasts between 2 and 7 days with the most women having periods of between 3 and 5 days.


The endometrium (uterus lining) contains an enzyme (plasmin) that prevents the blood from clotting. You may however see clots in your menstrual flow from time to time. The clots can be bright red to dark in color. The clots will most often make their appearance on the heaviest days of your period. This may make your period flow seem thicker and denser than usual.

These clots are forming because of the normal clotting that takes place in blood. Your body releases anticoagulants (a chemical that prevents blood from clotting) to keep menstrual blood in liquid form and not clotting as it flows out. When your flow is heavy and blood is being rapidly expelled, the anticoagulants get overwhelmed and there is not enough time for anticoagulants to work. This enables clots to form.

If you have excessive clotting or clots larger than about 25 mm (about an inch), you should see a health care provider to check for any conditions that might be causing an abnormal period.

Color and Thickness

Sometimes you may notice that your menstrual blood becomes dark brown to almost black as you near the end of your period. This is a normal color change and happens when the blood is not being expelled from the body quickly and gets ‘old’ inside your body.

Thick and heavy flow from time to time isn’t necessarily a cause for concern. If you regularly have heavy periods, you should speak to your health care provider to check your blood counts. Many women will become accustomed to heavy periods and consider them to be normal. Over time, though, the excess monthly blood loss leads to anemia, potentially causing weakness or fatigue. If you ever feel something’s not right with your period, see your health care provider.

What causes menstrual blood problems?

Changes in color and thickness of menstrual blood are often normal. But there are a number of problems that might cause abnormal clots to form in your menstrual blood or lead to the changes in color or thickness during your period. Remember, it’s important to discuss any concerns you have with your doctor. Problems that can cause changes include:

  • Miscarriage. Women who have miscarried may pass blood clots or gray/white clumps of tissue from the vagina. If there is a chance you are pregnant, be sure to check with your doctor immediately if you notice excessive bleeding or clotting. Often the fertilized egg will fail to implant due to genetic problems that will cause a danger to the mother or a very abnormal fetus. This egg will be ejected with menstrual flow. The flow is normally a few days late and abnormally light and the egg can often be seen in the menstrual flow.
  • Fibroids. Uterine fibroids are also called fibromyomas. These are non-cancerous tumors that form in the womb. Fibroids do not always cause symptoms. It is however common for women with fibroids to notice greater than usual amounts of menstrual blood. If you have fibroids, you may also have more clots in your period than you had in the past.
  • Hormonal changes. Your body relies on the delicate balance of the hormones progesterone and estrogen to regulate your menstrual cycle. These hormones regulate ovulation and the production and shedding of the uterine lining. When this balance is disturbed, it can lead to the development of an excessively thick uterine lining. This thickness can contribute to more bleeding than usual. It can also cause clots in the menstrual blood when the lining is shed.

Hormone changes may occur for many reasons, including:

  • Menopause
  • Recent dramatic weight change
  • Side effects from some medications, including steroids
  • Large uterus – If your uterus has been stretched during pregnancy and does not return to its original size, it may be permanently enlarged. With an enlarged uterus, menstrual blood may have time to collect and clot before it’s released from the body. This could also result in a dark color or thickening of your menstrual flow.
  • Obstruction of menstrual blood – Anything that hinders or blocks the flow of menstrual blood from the uterus through the cervix and out of the vagina may lead to problems with clots, color, or thickness of menstrual blood. Benign polyps in the uterus may change the flow of blood during your period. The flow can also be slowed around the time of menopause when the cervical canal may become smaller as estrogen levels drop.
  • Adenomyosis or Endometriosis – These two related conditions occur when the tissue that forms the uterine lining is found in the wrong place. Endometriosis is when this tissue develops outside of the uterus. Adenomyosis it when it grows in the muscle that makes up the uterine walls. Both of these conditions can lead to abnormal periods and heavy flow. This can increase the likelihood of menstrual problems such as clotting or thickness.

How will a doctor diagnose menstrual bleeding problems?

A wide variety of diagnostic tools are available to modern health care providers. Depending on your symptoms, the tests may include the following tests:

  • Vaginal Ultrasound. This test uses sound waves to take a picture of the inside of your vagina and uterus.
  • MRI. This non-invasive procedure can provide an image of growths, such as fibroids, that may be contributing to your menstrual bleeding problems.
  • Blood tests – Blood tests can determine whether your blood is clotting correctly. Your blood will also be tested for low iron (anemia),
  • Biopsy. A small tissue sample from the lining of your uterus will be analyzed.
  • Dilatation and Curettage (D&C) – The cervix is dilated and a surgeon scrapes off the lining of the uterus and cervix. This can be used to help alleviate excessive bleeding or obtain tissue samples for analysis.

When to seek help

Menstrual bleeding problems are seldom serious. Because of its gradual nature, significant blood loss can occur over time and go unnoticed. See your medical care providers if you experience any of the following:

  • Fatigue with normal activity
  • Lightheadedness
  • Pale, white skin
  • Fingernail beds that are pale, not pink
  • Very irregular periods
  • Frequent bleeding in between periods
  • Amenorrhea – no menstruation for extended periods of time during your fertile years (late puberty to menopause) except when breast feeding
  • Extremely heavy bleeding
  • Bleeding that does not stop

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