Unscheduled Bleeding on HRT: When to Worry and What Gets Checked

In the first few months, usually yes. Understanding why requires knowing which type of HRT you are on, because the two regimens are designed to do completely different things with your bleeding.

Sequential (cyclical) HRT gives estrogen continuously and progestogen for 10 to 14 days per month. It is the usual choice for perimenopausal women who are still having some periods. It is designed to produce a predictable monthly withdrawal bleed, typically starting toward the end of or just after the progestogen phase. That bleed is the regimen working as intended. It is scheduled, not unscheduled.

Continuous combined HRT gives both hormones every day with no break. It is the standard for women who are more than twelve months past their final period. The goal is no bleeding at all. Getting there takes time, because the endometrium, the lining of the uterus, has to adapt to constant low-dose progestogen exposure and become thin and stable. During that adjustment period, unpredictable spotting and light bleeding are common, and a substantial minority of women experience it in the first three to six months.

Why it happens: constant progestogen makes the endometrium atrophic, but the process is uneven. Fragile superficial vessels break down at different rates in different areas, producing irregular spotting until the whole lining stabilises. This is the same physiology that makes progestogen-only contraception unpredictable at the start.

The reassuring version of the rule: bleeding in the first six months of continuous combined HRT that is settling rather than worsening is usually just the adjustment happening. Our guide to [HRT side effects in the first three months](/blog/hrt-side-effects-first-3-months-whats-normal) covers what else falls into this window.

The part that matters: this grace period has an expiry date, and using it to explain away bleeding at month nine is where problems get missed.

There are five patterns that move bleeding from the expected column to the investigate column, and they are worth knowing precisely because the reassurance around early bleeding is so widely repeated.

1. Bleeding that begins after six months on continuous combined HRT. The adjustment window has passed. New bleeding after it is unscheduled by definition.

2. Bleeding that restarts after a settled bleed-free period. If you had no bleeding for four months and it has now returned, the change itself is the signal, regardless of how light it is or how long you have been on HRT.

3. Heavy bleeding at any point. Soaking through protection hourly, passing clots larger than a 10p coin or a quarter, or flooding. This is not part of normal adjustment. Our guide to [heavy bleeding in perimenopause](/blog/heavy-bleeding-in-perimenopause-when-flooding-isnt-normal) covers what heavy actually means clinically.

4. Bleeding after sex. Postcoital bleeding is never in the expected category and points toward the cervix or vaginal tissue rather than the endometrium. It is often caused by genitourinary syndrome of menopause, where thin fragile tissue bleeds easily, and that is very treatable, as covered in [vaginal estrogen for GSM](/blog/vaginal-estrogen-for-gsm-safety-types-and-what-to-expect). But it needs looking at rather than assuming.

5. Bleeding with pain, unintended weight loss, or unusual discharge. Any of these alongside bleeding raises the priority.

The underlying reason for taking these seriously is simple. Estrogen stimulates the endometrium to grow; progestogen opposes that growth. If the progestogen component is insufficient, absent, or not being absorbed, the lining can thicken abnormally. That is endometrial hyperplasia, and a subset of hyperplasia with atypical cells can progress to endometrial cancer. This is precisely why progestogen is prescribed alongside estrogen for anyone with a uterus, as explained in [what progesterone does and why you need it](/blog/progesterone-in-menopause-what-it-does-and-why-you-need-it).

Most investigated bleeding turns out to be benign. The point of investigating is that the small proportion that is not is highly treatable when caught early.

Before anyone reaches for a scan, most clinicians work through a list of ordinary explanations, several of which you can check yourself tonight.

Adherence and absorption. Missed doses are the single most common cause. A skipped progestogen capsule, patches that lift at the edges after a shower or in hot weather, gel applied to a different area than usual, or a sachet applied over body lotion, all reduce the progestogen reaching the endometrium. Vomiting or diarrhoea within a few hours of an oral dose does the same thing.

Insufficient progestogen for the estrogen dose. If your estrogen dose was recently increased and the progestogen was not reviewed alongside it, the balance may now be off. This is a common trigger and a straightforward fix, discussed further in [patch versus pill versus gel](/blog/hrt-patch-vs-pill-vs-gel-which-is-safest).

Drug interactions. Some medications speed up how quickly the liver clears estrogen and progestogen, lowering effective levels. The list includes certain anti-epileptics such as carbamazepine, rifampicin, and the herbal supplement St John's Wort, which people frequently take for low mood without mentioning it because it is not a prescription drug. Always mention it.

Structural causes. Endometrial or cervical polyps are common in this age group and benign in the large majority of cases, but they bleed. Fibroids can do the same, particularly those distorting the uterine cavity.

Local tissue fragility. Genitourinary syndrome of menopause thins vaginal and cervical tissue, which can bleed with minimal contact.

Infection. Less common, but cervicitis and endometritis both cause bleeding and are easily diagnosed.

Pregnancy. Rarely considered and occasionally the answer, particularly in perimenopausal women on sequential HRT who have assumed they are no longer fertile. Contraception is still needed until 12 months after the final period if over 50, or 24 months if under 50, as covered in [birth control in perimenopause](/blog/birth-control-in-perimenopause-what-to-use-after-40).

The workup is more predictable than most people expect, and knowing the sequence removes a lot of the anxiety around the appointment.

History and examination first. Your clinician will want the pattern: when it started, how heavy, whether it relates to your progestogen phase, whether it follows intercourse. Then a speculum examination to look directly at the cervix and vaginal walls, because a visible polyp or an area of fragile atrophic tissue can explain everything and is identified in minutes. A cervical screening test is often done at the same time if you are due.

Transvaginal ultrasound. This is the workhorse. It measures endometrial thickness, and the threshold is what drives everything downstream. In a postmenopausal woman with bleeding, an endometrial thickness of 4 mm or less has a very high negative predictive value for endometrial cancer, so a thin lining is genuinely reassuring. Above 4 mm, tissue sampling follows (ACOG Committee Opinion 734). The scan also identifies polyps, fibroids and ovarian abnormalities.

One nuance worth knowing: the 4 mm threshold was validated in postmenopausal women not taking hormone therapy. In women on sequential HRT the endometrium is expected to be thicker at certain points in the cycle, so timing the scan matters and interpretation is less clear-cut. Your clinician may schedule the scan for a specific point in your cycle for this reason.

Endometrial biopsy. Usually done in clinic with a thin flexible sampler passed through the cervix. It takes a few minutes and typically causes cramping similar to a strong period pain. Taking ibuprofen an hour beforehand genuinely helps. It samples the lining to check for hyperplasia or malignancy.

Hysteroscopy. A thin camera passed into the uterine cavity, used when the ultrasound suggests a polyp, when a biopsy was inconclusive, or when bleeding persists despite a normal workup. Polyps can often be removed during the same procedure.

Most women complete this pathway with a benign result. The purpose is to convert uncertainty into an answer.

Once serious causes are ruled out, the goal shifts to making the regimen work for you, and there are several levers. Importantly, stopping HRT is rarely the first one.

Increase or change the progestogen. The most common adjustment. That might mean a higher dose, a different molecule, or switching from a synthetic progestogen to micronised progesterone, which many women tolerate better.

Consider a levonorgestrel intrauterine system. The hormonal coil, such as Mirena, delivers progestogen directly to the endometrium and is licensed in the UK as the progestogen component of HRT. It is frequently the most effective solution for persistent bleeding because it acts locally at high concentration with minimal systemic exposure, and many women stop bleeding entirely.

Adjust the estrogen. If the estrogen dose is higher than your symptoms actually require, reducing it slightly can settle bleeding without losing symptom control.

Change from sequential to continuous combined. If you are more than a year past your final period and still on sequential HRT, switching removes the monthly bleed altogether. This is often overlooked simply because nobody revisited the regimen.

Fix the mundane things. Set a phone alarm for the progestogen. Apply patches to clean dry skin away from lotion and change them on schedule. Rotate gel application sites consistently. Review supplements, including St John's Wort.

Treat local tissue. If postcoital bleeding is coming from atrophic tissue, vaginal estrogen resolves it in most cases and can be used alongside systemic HRT.

A closing point on proportion. Investigating bleeding is not a sign that something is likely wrong; it is what makes staying on HRT safe. The overall picture on duration and safety is covered in [how long you can stay on HRT](/blog/how-long-can-you-stay-on-hrt-duration-explained). Being investigated once is a normal part of a long HRT course, not a reason to abandon treatment that is helping you.