You have had an ultrasound for abnormal bleeding, and the report says your endometrial thickness is a number in millimetres. Nobody explains what the number means, whether it is good or bad, or why a biopsy was or was not suggested. Here is how these tests are used and what to ask.

Where we stand: Menova is an independent publication. We sell no tests, we are not your doctor, and this is general education, not a diagnosis. Thresholds and protocols vary by country and by individual circumstance — your result must be interpreted by your own clinician.

What is being measured

A transvaginal ultrasound measures the thickness of the endometrium, the lining of the womb. A probe is placed in the vagina, which gives a much clearer image than a scan through the abdomen. It takes a few minutes and is usually uncomfortable rather than painful.

The lining thickens and sheds in response to hormones. After menopause, with low estrogen, it should be thin. A thickened lining in a postmenopausal woman is the finding that prompts further investigation.

Why a number alone tells you little

The same measurement means different things depending on who you are.

If you are postmenopausal and not on hormone therapy, a thin lining below the local threshold makes endometrial cancer very unlikely, and many protocols stop there when bleeding has settled. Commonly cited thresholds sit in the region of 3 to 5mm, but they differ between guidelines and countries.

If you are on hormone therapy, the lining is expected to be thicker, and it varies with the regimen — cyclical therapy produces a lining that changes through the month, so when in your cycle the scan was done matters. Applying a no-HRT threshold to a woman on cyclical HRT produces unnecessary alarm.

If you are still in perimenopause, thickness varies enormously across a normal cycle and is far less useful as a screening measure.

If you take tamoxifen, the lining commonly appears thickened and irregular, and this is interpreted differently again.

So the first question is not "is my number high?" but "what is the threshold for someone in my situation?"

Tell whoever scans you exactly what you take, including vaginal estrogen — see bleeding on HRT.

What else the scan shows

Thickness is not the only finding. The scan also looks at:

A saline infusion sonogram, where a small amount of fluid is put into the cavity during the scan, distinguishes a polyp from generalised thickening better than a standard scan.

When a biopsy is suggested

An endometrial biopsy samples the lining. It is usually suggested when:

  • The lining is thicker than the threshold for your situation
  • Bleeding persists despite a thin lining, because a thin measurement does not exclude everything
  • You have risk factors that lower the threshold for investigating
  • The scan shows something focal or irregular

What it involves: a speculum examination, then a thin flexible tube passed through the cervix to take a sample by suction. It takes a few minutes.

What it feels like: most women describe strong period-type cramping during and shortly after. Some find it straightforward; some find it genuinely painful.

What to ask for in advance — and this is the practical part most women are not told:

  • Take simple painkillers about an hour beforehand, if you can take them
  • Ask whether local anaesthetic is available
  • Say if you have found examinations difficult before, have a history of trauma, or are very anxious — options including a general anaesthetic exist and are legitimate to discuss
  • Ask if you can bring someone
  • Arrange not to drive if you are anxious about how you will feel
  • Ask them to stop if you need them to. You are allowed to say this at any point

Pain in gynaecological procedures has been under-acknowledged for a long time. Asking about pain relief in advance is not being difficult.

Hysteroscopy

A camera examination of the inside of the womb, used when a polyp or focal abnormality is suspected, or when a biopsy was inconclusive.

It can be done in an outpatient clinic while you are awake, or under general anaesthetic. Both are valid options and you can ask which is available. Outpatient hysteroscopy is quick and many women manage it easily; a proportion find it very painful, and the difference is not predictable in advance.

Polyps can often be removed during the same procedure.

The same pain-relief questions apply, and more strongly.

Understanding the result

Possible findings, in plain terms:

  • Atrophic endometrium — a thin, inactive lining. Common after menopause and a reassuring result. Bleeding from atrophy is often treated effectively with local vaginal estrogen; see is vaginal estrogen safe
  • Proliferative or secretory endometrium — normal lining under hormonal influence
  • Polyp — usually benign, often removed
  • Hyperplasia without atypia — a thickened lining with a low risk of progression, usually treated with progestogen, often a hormonal IUD, then rechecked
  • Hyperplasia with atypia — carries a meaningful risk of progressing, and is managed more actively, often surgically
  • Insufficient sample — common, particularly with a thin atrophic lining. It usually means the sample could not be obtained rather than that anything is wrong, but it may need repeating if bleeding continues

Ask for your result in plain language, and ask what the plan is: repeat scan, treatment, or discharge.

Questions worth asking

  • "What threshold applies to me, given what I take?"
  • "Was the scan done at the right point in my cycle?"
  • "Is this generalised thickening or a focal lesion?"
  • "What are the options for pain relief for the biopsy?"
  • "If the biopsy is normal but I keep bleeding, what happens next?"
  • "When will I get results, and how will they reach me?"

That last one prevents a great deal of waiting-room anxiety.

What not to do

Do not treat a normal scan as permission to ignore ongoing bleeding. A thin lining reduces the likelihood of some things but does not exclude everything, and persistent bleeding warrants further assessment regardless of a reassuring scan. If bleeding continues, go back — see bleeding after menopause.

Our free printable visit prep sheet gives you a page for your medication list and questions, and the free 30-day symptom tracker records the bleeding pattern that drives the decisions.

The free 2-minute Menova self-check organizes your wider symptom picture — no account, not a diagnosis, and your answers never leave your device.

This article is general education, not medical advice or a diagnosis. Thresholds and protocols differ by country, guideline body and individual circumstances. Your results must be interpreted by a licensed clinician who knows your full history.

Sources: ACOG — Perimenopausal and Postmenopausal Bleeding, National Cancer Institute — Uterine Cancer, NHS — Hysteroscopy, and The Menopause Society.