Hormonal health

Adenomyosis or Fibroids? How Doctors Tell Them Apart

Save

Adenomyosis and fibroids both enlarge the uterus and cause heavy, painful periods. Fibroids are discrete growths, while adenomyosis is diffuse thickening of the uterine wall. Fibroids are the most common benign uterine tumor. Doctors distinguish them with transvaginal ultrasound and MRI, since each looks different on imaging.

Last updated: July 2026

Talk to a clinician

Gale can help you find a clinician in your state and request a visit.

Find care →

What is the difference between adenomyosis and fibroids?

Fibroids are discrete lumps, while adenomyosis is a diffuse change woven through the uterine muscle. Fibroids, also called leiomyomas, are firm, well-defined growths of muscle and fibrous tissue, and according to ACOG they are the most common benign tumor of the uterus, developing in as many as 8 in 10 women by age 50 1. Adenomyosis instead thickens the uterine wall broadly, so the whole uterus feels bulky and tender rather than lumpy. Both are estrogen-sensitive, both can cause heavy periods, and confusingly, both can be present at once. Getting clear on how to tell if you have fibroids is a natural starting point, since fibroids are the more familiar of the two.

Do they cause different symptoms?

Both cause heavy periods and pelvic pressure, but the pain pattern tends to differ. Adenomyosis usually brings diffuse, cramping pain and a tender uterus that worsens with periods. Fibroids often cause bulk and pressure, sometimes on the bladder or bowel, and can be painless unless they outgrow their blood supply. Either way, heavy menstrual bleeding that interferes with daily life is worth assessing, and the NICE guideline recommends investigating it 2. Heavy, prolonged bleeding can also lower iron stores over time, so fatigue and breathlessness may signal anemia that a ferritin test can flag 3. Endometriosis, which affects about 10% of women, or roughly 1 in 10, can accompany either condition and add to the pelvic pain 4. The overlap in symptoms is exactly why imaging usually decides the question.

How do doctors tell them apart on imaging?

Imaging is the main way clinicians separate the two, because each has a characteristic appearance. A transvaginal ultrasound is typically the first test when the uterus feels bulky or periods are heavy 2. Fibroids usually show up as well-defined, rounded masses that can be measured and mapped, whereas adenomyosis appears as diffuse, ill-defined thickening, often with a globular uterus and small cysts in the muscle. MRI adds detail when the picture is unclear or when the two coexist, and it is especially useful for planning treatment. A closer look at how adenomyosis is diagnosed on imaging explains the specific clues radiologists rely on.

Does the treatment differ?

Treatment choices diverge once the diagnosis is clear. Fibroids have a wide menu of options, from hormonal medicines and a hormonal IUD to procedures such as myomectomy, which removes the growths, and uterine artery embolization, which shrinks them 5. Adenomyosis is managed mainly by lowering or steadying estrogen with hormonal methods or GnRH medicines, with everyday pain relievers used for cramps; removing the uterus resolves it definitively. Both are estrogen-driven, so symptoms of each usually ease after menopause, and both are most often diagnosed in the 40s. Reviewing fibroid treatment options shows how the paths differ once the cause is named.

When sorting adenomyosis from fibroids needs a clinician

A bulky uterus or heavy periods that affect daily life is a reason to seek evaluation, whatever the cause. A clinician can examine you, arrange a transvaginal ultrasound, and add MRI if the diagnosis is uncertain or if adenomyosis and fibroids seem to coexist. Sorting out which condition is driving the symptoms matters, because it changes the treatment options and the fertility conversation. A blood test can also check for the anemia that heavy bleeding causes. Naming the cause turns a vague enlarged uterus into a clear plan you and your clinician can act on together.

Common questions

Yes. Both are common, estrogen-driven conditions of the uterus, and they frequently occur in the same person. When both are present, imaging, usually a transvaginal ultrasound with MRI added when needed, helps sort out how much each is contributing to heavy bleeding and pain, which in turn shapes treatment.

It can be, because both enlarge the uterus and cause heavy, painful periods. Fibroids are more familiar and easier to see as discrete masses on ultrasound, so a bulky uterus is sometimes attributed to fibroids when diffuse adenomyosis is also present. A careful ultrasound, and MRI when needed, reduces that confusion.

Sometimes. Adenomyosis tends to cause diffuse, cramping pain and a tender uterus that worsens with periods, while fibroids often cause pressure and bulk and may be painless unless they degenerate. Because the patterns overlap, symptoms alone rarely settle the question, and imaging usually provides the answer.

Both are estrogen-driven, so symptoms usually ease after menopause as hormone levels fall. Fibroids often shrink, and adenomyosis-related bleeding and pain tend to settle. Before menopause, though, symptoms can be significant, and many effective treatments are available to manage them in the meantime.

Related

Say it back

How would you explain this to someone you love?

Two or three sentences, just as you’d say it. Gale reflects back what you focused on — a mirror, not a quiz.

Talk to a clinician

Gale can help you find a clinician in your state and request a visit.

Find care →

When an enlarged uterus or heavy periods need review

  • —Soaking through a pad or tampon every hour, or passing large clots, is a reason to seek same-day care.
  • —Fatigue, dizziness, a rapid heartbeat, or breathlessness with heavy periods is a reason to be checked for anemia.
  • —Sudden, severe pelvic pain, especially with fever, warrants urgent medical evaluation.
  • —Rapid enlargement of the abdomen, or new pressure on the bladder or bowel, is a reason to arrange prompt review.
  • —Bleeding after menopause is a reason to seek a clinician's assessment without delay.

If you are soaking through a pad every hour, passing very large clots, or feel faint or short of breath, seek urgent care or go to the nearest emergency room as soon as possible.

This article is general health education, not medical advice. Telling adenomyosis from fibroids, and choosing treatment, should be done with a gynecologist who knows your history.

References

  1. 1.American College of Obstetricians and Gynecologists (2021). Management of Symptomatic Uterine Leiomyomas: ACOG Practice Bulletin, Number 228. Obstetrics & Gynecology. doi:10.1097/AOG.0000000000004401 ✓Guidance describing uterine leiomyomas (fibroids) as the most common benign tumor of the uterus, developing in the majority of women by age 50, and the range of treatments including myomectomy and hormonal therapy.
  2. 2.National Institute for Health and Care Excellence (2026). Heavy menstrual bleeding: assessment and management (NG88). National Institute for Health and Care Excellence (NICE). link ✓Guidance that heavy menstrual bleeding interfering with quality of life should be investigated, with ultrasound as a first-line investigation for a bulky uterus or suspected structural cause.
  3. 3.MedlinePlus (National Library of Medicine) (2025). Ferritin Blood Test. MedlinePlus, U.S. National Library of Medicine (NIH). link ✓Explanation that heavy or prolonged menstrual bleeding is a common cause of low iron, which a ferritin blood test measures.
  4. 4.World Health Organization (2025). Endometriosis (fact sheet). World Health Organization (WHO). link ✓Global prevalence of endometriosis (about 10%, roughly 1 in 10 reproductive-age women), the condition that can coexist with adenomyosis and fibroids.
  5. 5.Hartmann KE, Fonnesbeck C, Surawicz T, Krishnaswami S, Andrews JC, Wilson JE, Velez-Edwards D, Kugley S, Sathe NA (2017). Management of Uterine Fibroids (Comparative Effectiveness Review No. 195). Agency for Healthcare Research and Quality (AHRQ). PMID 30789683 ✓Comparative review of fibroid treatments, including myomectomy and uterine artery embolization.

5 sources, numbered by first appearance. General health information, not medical advice. AI-assisted editorial content — every citation independently verified. Editorial policy

← Back to the health library