Why HRT includes a progestogen if you have a womb

If you have a womb, HRT is almost always two hormones, not one. Oestrogen relieves symptoms. A progestogen is there to protect the lining of the womb. Understanding that second part explains a lot about how HRT is prescribed, and some of its side effects.

This article describes what the guidance says. It is not advice about your own treatment, which is a conversation for you and the clinician who prescribes it.

The short version

NICE recommends offering combined HRT, oestrogen with a progestogen, to people with a uterus, and oestrogen-only HRT to people who have had a total hysterectomy ¹. The NHS explains why: taking both helps protect against the risk of womb cancer ².

The progestogen can be a tablet, part of a combined patch, or a hormonal coil ¹². It can be taken for part of each month or every day, depending mainly on whether you still have periods ².

What oestrogen alone does to the womb

In people with a uterus, NICE states that endometrial cancer risk increases with oestrogen-only HRT, whether taken orally or through the skin ¹.

NICE's discussion aid puts numbers on it for women aged 50 to 54, over five years ⁴:

• 4 in 1,000 women who never take HRT develop endometrial cancer
• 11 in 1,000 women with a uterus who take oestrogen-only HRT do, which is 7 more
• 1 in 1,000 women on continuous combined HRT do, which is 3 fewer than never taking HRT
• 8 in 1,000 women on sequential combined HRT do, which is 4 more

So the progestogen does more than cancel out the oestrogen effect. With continuous combined HRT, NICE says endometrial cancer risk decreases ¹.

Sequential or continuous

There are two ways to take the progestogen.

Sequential combined HRT, sometimes called cyclical, is usually suggested if you still have periods or have had one recently. Oestrogen is taken every day and the progestogen for the last 10 to 14 days of the cycle ².

Continuous combined HRT is usually suggested once periods have stopped. Both hormones are taken every day without a break ².

NICE notes that endometrial cancer risk may slightly increase with sequential HRT, and more so with longer use, fewer days of progestogen per cycle, and higher oestrogen doses ¹.

The progestogen options

The British Menopause Society lists the progestogens used in UK HRT, including micronised progesterone, dydrogesterone, medroxyprogesterone acetate, norethisterone, levonorgestrel and drospirenone ³. The dose needed depends on the oestrogen dose: a higher oestrogen dose needs more progestogen to protect the lining ³.

The hormonal coil is one of the options. The NHS describes the Mirena coil releasing progestogen over five years ², and the British Menopause Society lists the 52 mg levonorgestrel coil as providing protection for up to five years of use as part of HRT ³.

Progestogens and breast cancer

Combined HRT raises breast cancer risk more than oestrogen-only HRT does ¹. NICE says the risk with sequential combined HRT is lower than with continuous combined HRT, but higher than with no HRT ¹.

Micronised progesterone is often described online as the safer choice for breasts. NICE's position is more cautious: there is insufficient evidence to establish whether the breast cancer risk differs with micronised progesterone or dydrogesterone compared with other progestogens ¹. The guide to HRT and breast cancer on this site has the numbers.

Side effects from the progestogen

The British Menopause Society lists common progestogen side effects as fluid retention, breast tenderness, headaches, mood swings and symptoms like premenstrual tension ³. Its suggested responses include changing the type of progestogen, reducing the dose where possible, changing the route, or altering the duration ³.

If you notice a pattern, such as low mood on the days you take a sequential progestogen, that is worth writing down. Working out which hormone is causing a side effect is one of the first steps the British Menopause Society suggests ³.

Get checked: bleeding outside the expected windows

NICE advises that bleeding is common in the first six months of HRT and within three months of a change, and that unscheduled bleeding beyond those windows needs prompt medical help ¹. The guide to irregular bleeding on this site covers the details.

Guidance in the US and Europe

The US position matches NICE's. When the FDA removed several boxed warnings from hormone therapy in 2025, it kept the boxed warning about endometrial cancer for systemic estrogen-alone products ⁵. Its 2026 label changes included progestogen products used by women with a uterus who take systemic estrogen ⁶. The Menopause Society lists whether a progestogen is used among the factors that change the risks of hormone therapy ⁷.

In Europe, the European Menopause and Andropause Society (EMAS) says the choice of treatment should be individualised to each woman's age, symptoms, risk profile and preference ⁸.

What is still uncertain

How the different progestogens compare on mood, sleep and breast cancer risk is not settled, and NICE says so directly for breast cancer ¹. Choosing one is often a matter of trying, recording and reviewing.

Keeping a record

Note which progestogen you take, how, and on which days. Halcyon logs each regimen change on the same timeline as your symptoms and side effects, so a review can see what changed and when.