Abnormal Uterine Bleeding: When Is It Normal, and When Should It Be Evaluated?

Many people assume that abnormal uterine bleeding is simply "part of having a uterus." In reality, changes in menstrual bleeding can sometimes be the first sign of an underlying medical condition that deserves evaluation.

The good news is that most abnormal bleeding is not caused by cancer. It is often related to hormonal changes, benign growths such as fibroids or polyps, medications, or other treatable conditions. However, because serious causes can occasionally present in the same way, it's important to approach abnormal bleeding thoughtfully rather than dismissing it.

What Counts as Abnormal Uterine Bleeding?

Abnormal uterine bleeding (AUB) refers to bleeding from the uterus that differs from your usual pattern. This may include:

• Periods that are much heavier than normal

• Bleeding that lasts longer than expected

• Bleeding between periods

• Very frequent or very infrequent periods

• Bleeding after sex

• Bleeding after menopause

• Bleeding that causes anemia, dizziness, or significantly affects daily life

Everyone's "normal" is different. The important question is whether your bleeding has changed from your usual pattern or is interfering with your health or quality of life.

The First Questions Your Clinician Will Ask

The evaluation begins long before any tests are ordered.

Your clinician will want to understand:

• When the bleeding started

• How heavy it is (including flooding, large clots, or bleeding through clothing)

• How long it lasts

• Whether your cycles have become irregular

• Whether you're experiencing pelvic pain, fever, unusual discharge, or pain with intercourse

• Whether you could be pregnant

• What medications or hormones you're taking

• Whether you've recently started, stopped, or missed hormonal medications

• Whether you have symptoms of anemia such as fatigue, dizziness, or shortness of breath

• Whether you have risk factors for uterine cancer or inherited bleeding disorders

These questions help determine which causes are most likely and which tests will actually be useful.

Pregnancy Comes First

If pregnancy is biologically possible, the first step is almost always a pregnancy test.

Pregnancy-related bleeding follows a completely different diagnostic pathway than non-pregnancy-related bleeding. Even people using contraception or those who believe pregnancy is unlikely may still be tested because early pregnancy complications can occasionally be life-threatening.

Is It an Emergency?

Most abnormal bleeding does not require emergency care.

However, seek immediate medical attention if you have:

• Heavy bleeding causing fainting or near-fainting

• Severe dizziness

• Chest pain or shortness of breath

• Rapid heartbeat with heavy bleeding

• Bleeding that soaks through multiple pads per hour for several hours

• Severe pelvic pain, especially during pregnancy

• Signs of severe anemia

  
  

Understanding the Causes: The PALM-COEIN System

Gynecologists use an internationally recognized system called PALM-COEIN to organize the possible causes of abnormal uterine bleeding.

Structural causes (things you can often see on imaging)

P – PolypsSmall growths inside the uterus or cervix.

A – AdenomyosisThe uterine lining grows into the muscular wall of the uterus.

L – Leiomyomas (Fibroids)Benign tumors made of muscle tissue.

M – Malignancy and HyperplasiaPrecancerous changes or cancer of the uterine lining.

Non-structural causes

C – CoagulopathyBleeding disorders such as von Willebrand disease.

O – Ovulatory dysfunctionIrregular ovulation, common with PCOS, thyroid disease, stress, significant weight changes, adolescence, and perimenopause.

E – Endometrial causesProblems with the uterine lining itself despite normal hormones and anatomy.

I – IatrogenicBleeding caused by medications or medical treatments, including hormonal contraception, menopausal hormone therapy, tamoxifen, or anticoagulants.

N – Not otherwise classifiedLess common causes that don't fit into the other categories.

Blood Tests

Not everyone needs extensive laboratory testing.

Depending on your symptoms, your clinician may recommend:

• Complete blood count (CBC) to look for anemia

• Ferritin to evaluate iron stores

• Pregnancy testing

• Thyroid testing (when indicated)

• Testing for bleeding disorders if your history suggests one

• Other hormone testing only when clinically appropriate

  
  

Testing should be guided by your history rather than performed routinely for everyone.

Ultrasound and Biopsy Answer Different Questions

A common misconception is that an ultrasound alone can rule out cancer. This is NOT the case. These tests provide different information.

Ultrasound helps identify:

• Fibroids

• Polyps

• Ovarian cysts

• Adenomyosis

• Other structural abnormalities

  
  

Endometrial biopsy evaluates:

• The cells lining the uterus

• Endometrial hyperplasia (precancer)

• Endometrial cancer

  
  

Because these tests answer different questions, some patients need one, while others benefit from both. If bleeding continues despite a normal biopsy, additional evaluation may still be necessary because a blind biopsy can occasionally miss focal abnormalities such as polyps.

A Special Note About Perimenopause

Perimenopause is one of the most common times for bleeding patterns to change.

Although hormonal fluctuations often explain irregular bleeding during this stage of life, not every episode should automatically be blamed on menopause.

Risk factors, symptoms, age, hormone therapy, and individual circumstances determine whether additional evaluation—including imaging or biopsy—is appropriate.

Importantly, endometrial thickness should not be used by itself to rule out cancer in premenopausal or perimenopausal patients. Unlike after menopause, the uterine lining naturally changes throughout the menstrual cycle, making thickness measurements much less reliable.

Bleeding After Menopause

Any bleeding after menopause deserves medical evaluation.

While many causes are benign—including vaginal thinning, polyps, or hormone therapy—postmenopausal bleeding can also be an early sign of endometrial cancer. Early evaluation greatly improves the chance of detecting problems while they are highly treatable.

Special Situations

Some people require a slightly different approach, including:

• Adolescents (where irregular cycles can be normal for the first 2–3 years after the first menstrual period)

• People with inherited bleeding disorders

• Individuals taking blood thinners

• Those with prior cesarean deliveries (who may develop cesarean scar defects)

• People using hormonal contraception or menopausal hormone therapy

• Transgender and gender-diverse patients, whose evaluation depends on their anatomy, hormone regimen, pregnancy potential, and individual goals

  
  

Every evaluation should be individualized rather than based on assumptions.

Trauma-Informed and Inclusive Care Matters

Pelvic bleeding evaluations can feel vulnerable or even frightening.

A good evaluation should include:

• Shared decision-making

• Trauma-informed care

• Pain management during procedures when appropriate

• Respect for your gender identity and reproductive goals

• Clear explanations about why tests are being recommended

• Reliable follow-up for imaging and biopsy results

  
  

You deserve to understand what is happening and to participate in decisions about your care.

When Should You See a Healthcare Professional?

Schedule an evaluation if you experience:

• Bleeding between periods

• Very heavy periods

• Bleeding lasting more than about a week

• Bleeding after menopause

• Bleeding after sex

• New irregular bleeding

• Symptoms of anemia

• Bleeding that is significantly different from your usual pattern

  
  

Most causes of abnormal uterine bleeding are treatable. Getting evaluated early can help identify the cause, improve symptoms, prevent complications such as iron deficiency, and—when necessary—detect serious conditions as early as possible.

Learn More

1. American College of Obstetricians and Gynecologists. (2012). Diagnosis of abnormal uterine bleeding in reproductive-aged women (Practice Bulletin No. 128). Obstetrics & Gynecology, 120(1), 197–206. https://doi.org/10.1097/AOG.0b013e318262e320

2. Dreisler, E., Frandsen, C. S., & Ulrich, L. G. (2024). Perimenopausal abnormal uterine bleeding. Maturitas, 188, 108054. https://doi.org/10.1016/j.maturitas.2024.108054

3. Jain, V., Munro, M. G., & Critchley, H. O. D. (2023). Contemporary evaluation of women and girls with abnormal uterine bleeding: FIGO Systems 1 and 2. International Journal of Gynecology & Obstetrics, 163(Suppl. 2), 3–17. https://doi.org/10.1002/ijgo.14926

4. Wouk, N., & Helton, M. (2019). Abnormal uterine bleeding in premenopausal women. American Family Physician, 99(7), 435–443.

5. American College of Obstetricians and Gynecologists. Patient education resources on abnormal uterine bleeding and heavy menstrual bleeding: https://www.acog.org/womens-health

6. International Federation of Gynecology and Obstetrics (FIGO). Classification systems for abnormal uterine bleeding: https://www.figo.org