After menopause, the lining of the womb (the endometrium) normally becomes thin. In a woman who has had bleeding after menopause, an endometrial thickness of 4 mm or less on a transvaginal ultrasound is widely used as reassuring, and some guidelines use 3 mm. But the number only makes sense alongside the full picture: whether you are bleeding, whether you take HRT or tamoxifen, and your other risk factors. This guide explains what the measurement means, what counts as normal and what happens if yours is thicker.
What is endometrial thickness?
The endometrium is the inner lining of the womb. Before menopause, it thickens each month under the influence of oestrogen and progesterone and is shed as a period. Its thickness changes a great deal across the cycle, so there is no single "normal" number in younger women.
After menopause, oestrogen levels fall and the lining stops building up. It becomes thin and inactive, a state doctors call atrophic. If it is thicker than expected, it may simply be a normal variation, a benign polyp or the effect of hormones, but it can also be a sign of an overgrown lining (endometrial hyperplasia) or, less often, womb cancer.
The thickness is measured on a transvaginal ultrasound, where a slim probe is placed gently in the vagina. The Indian Menopause Society describes the standard measurement as the maximum front-to-back thickness of the lining, which on the report is often called the "endometrial echo" or "ET".
What is normal if you have had bleeding after menopause?
This is the situation the cut-offs were designed for. Any bleeding after menopause needs prompt assessment; our guide to bleeding after menopause explains why and what the causes are.
| Source | Threshold for a thin, reassuring lining |
|---|---|
| American College of Obstetricians and Gynecologists (2018) | 4 mm or less; a greater than 99% negative predictive value for endometrial cancer |
| Timmermans et al., meta-analysis (2010) | 3 mm recommended to exclude cancer, as earlier reviews may have overestimated the accuracy of higher cut-offs |
| Indian Menopause Society guidelines (2020) | 3–4 mm or less: sampling not usually required unless high risk or bleeding keeps recurring; consider sampling above 3–5 mm |
The Indian guidelines also give an idea of the trade-off. Used as a cut-off, 3 mm detected about 98% of cancers, 4 mm about 95% and 5 mm about 90%. The lower the threshold, the fewer cancers are missed, but the more women with harmless causes go on to have a biopsy.
The guidance is shifting towards biopsy
In 2026, the American College of Obstetricians and Gynecologists published a Clinical Practice Update recommending that most women with postmenopausal bleeding have both a transvaginal ultrasound and endometrial tissue sampling as part of their first assessment, rather than relying on a thin lining alone. The Indian Menopause Society similarly says women with postmenopausal bleeding may be assessed initially with both ultrasound and a biopsy. Your doctor may advise a biopsy even if your lining is thin, especially if bleeding happens again, the lining cannot be seen clearly, or you have risk factors.
What if you have no bleeding?
Many women discover their endometrial thickness by chance, on a scan done for another reason, such as an abdominal or pelvic check-up or an ovarian cyst. Here the rules are different.
- ACOG advises that a lining thicker than 4 mm found incidentally in a postmenopausal woman without bleeding does not need to trigger investigation routinely, though an individual assessment based on risk factors is appropriate.
- The Indian Menopause Society guidelines suggest a much higher threshold for prompting a biopsy in early postmenopausal women without symptoms (more than 11 mm), and do not recommend ultrasound screening for womb cancer in women without risk factors.
- ACOG also states that transvaginal ultrasound is not an appropriate screening test for endometrial cancer in women without bleeding.
So if your report says "ET 6 mm" and you have had no bleeding, it is not automatically a cause for alarm. Discuss it with your doctor, who will consider your age, weight, diabetes, other risks and the appearance of the lining on the scan.
What about HRT?
HRT can make the lining slightly thicker, and some bleeding is expected with certain regimens. That is why women who still have a womb are given a progestogen alongside oestrogen: it protects the lining from overgrowing. Oestrogen-only HRT without progestogen raises the risk of endometrial hyperplasia in women with a womb.
The Indian Menopause Society guidance gives a higher acceptable thickness of about 6 mm for women on menopausal hormone therapy. Unexpected bleeding on HRT, bleeding that starts after you have settled on treatment, or bleeding that continues beyond the first months, should still be checked. You can read more about how progestogen protects the womb on our progesterone page.
What about tamoxifen?
Tamoxifen, used to treat and prevent some breast cancers, acts like oestrogen on the womb lining. It often makes the lining look thicker on ultrasound and increases the risk of polyps, hyperplasia and womb cancer. Standard thickness cut-offs are less reliable in women taking it. The Indian guidelines advise follow-up and full evaluation as needed. Any bleeding on tamoxifen should be reported promptly to your doctor or oncology team.
What happens if your lining is thicker than expected?
Depending on your symptoms and risk factors, your doctor may suggest:
- Endometrial biopsy (pipelle): a thin tube takes a small sample of lining in the clinic, usually in a few minutes.
- Hysteroscopy: a thin camera looks inside the womb, so polyps can be seen and removed and targeted samples taken.
- Repeat scan: in some women without bleeding and at low risk, a follow-up scan may be appropriate.
Results commonly show an atrophic lining, a benign polyp or hyperplasia without atypia, which is usually treated with progestogen. Hyperplasia with atypical cells, or cancer, needs specialist gynaecology care. In the UK, NICE recommends fast-track suspected-cancer referral for women aged 55 and over with unexplained postmenopausal bleeding not attributable to HRT, and considering it for younger women.
Who is at higher risk?
A thicker lining is more concerning if you also have risk factors for womb cancer, including older age, excess weight, type 2 diabetes, polycystic ovary syndrome, oestrogen-only HRT without progestogen, tamoxifen use or a family history of gynaecological cancer. Tell your doctor about any of these.
When to see a doctor
- Any vaginal bleeding or spotting after menopause, however light.
- A new pink, brown or watery discharge.
- Unexpected or persistent bleeding on HRT.
- Any bleeding while taking tamoxifen.
- A scan report mentioning a thickened lining, a polyp or "fluid in the endometrial cavity".
Questions women ask
Is 5 mm endometrial thickness normal after menopause?
It depends. If you have had no bleeding, 5 mm is often not a concern on its own. If you have had bleeding, 5 mm is above the usual 3–4 mm thresholds, so a biopsy or further assessment is normally advised. Your doctor will also consider HRT use and other risk factors.
Is a thick lining always cancer?
No. Most thickened linings are caused by harmless changes such as polyps, hormone effects or hyperplasia without atypia. In a large 2018 review, about 9 in 100 women with postmenopausal bleeding were found to have womb cancer, so most did not. A biopsy is the way to know for certain.
Can a thin lining still be cancer?
Rarely, yes. Some cancers, particularly less common types, do not thicken the lining much. That is why many guidelines now recommend a biopsy along with the scan in most women who bleed, and why recurrent bleeding always needs further checks.
Can I reduce my endometrial thickness naturally?
There is no diet or supplement shown to thin the lining. If you are overweight, losing weight lowers oestrogen made by fat tissue and reduces womb cancer risk over time. If you take HRT and have a womb, make sure your regimen includes the right progestogen. Never ignore bleeding while trying lifestyle changes.
Does a transvaginal scan hurt?
Most women find it mildly uncomfortable rather than painful. After menopause, vaginal dryness can make it more uncomfortable; tell the sonographer, who can use extra gel and go slowly. You can ask for a female sonographer or a chaperone.
Have a scan report you would like explained, or bleeding you are worried about? Book a consultation with a NuHer doctor in person at Nariman Point, Mumbai, or by video from anywhere in India. For long-term health after menopause, see our guide to post-menopause care.
