Cyclical vs Continuous HRT Regimens

Women starting HRT often encounter terms like sequential, cyclical, and continuous combined without a clear explanation of what each means or which is appropriate at which stage. Getting this right matters: the wrong regimen can produce irregular bleeding that is inconvenient and, in some cases, clinically important to investigate.

The Two Main Regimen Types

Sequential (cyclical) HRT involves taking estrogen continuously, every day, with progestogen added for 10–14 days per month. At the end of the progestogen phase, the endometrium sheds, producing a predictable withdrawal bleed. Quarterly sequential regimens (progestogen every three months rather than monthly) are also used.

Continuous combined HRT involves taking both estrogen and progestogen every day without interruption. The progestogen prevents endometrial build-up throughout the cycle rather than triggering a monthly shed. The aim is amenorrhoea: no bleeding at all.

Both regimens provide endometrial protection when progestogen is used for an adequate number of days and at an adequate dose. Women who have had a hysterectomy need only estrogen and should use neither regimen's progestogen component.

Why Menopausal Stage Determines the Choice

In perimenopause, the ovaries are still producing some estrogen and progesterone, even if irregularly. The endometrium may still be responding to these variable hormonal signals. Starting continuous combined HRT at this stage typically produces unpredictable breakthrough bleeding because the endometrium is not in a stable hormonal environment. Sequential HRT mirrors the hormonal pattern of a normal menstrual cycle, is better tolerated, and produces more predictable bleeding.[1]

Sequential HRT during perimenopause has a secondary benefit: the monthly withdrawal bleed makes it easier to track whether a woman's own cycles have stopped. This matters for contraception decisions (perimenopausal women can still ovulate and become pregnant) and for knowing when to consider switching regimens.

In postmenopause (12 months after the last period), continuous combined HRT becomes appropriate. With no remaining endogenous hormonal variation, a stable daily progestogen can maintain the endometrium without triggering a monthly bleed. Since amenorrhoea is the goal for most postmenopausal women, continuous combined is the standard recommendation for this stage.[1][2]

Bleeding Patterns and What They Signal

On sequential HRT, regular monthly withdrawal bleeds are expected: occurring at the end of each progestogen phase, light to moderate, lasting a few days. Irregular bleeding (at unexpected times outside the withdrawal window, or absent when bleeding is expected) warrants clinical evaluation. It may indicate insufficient progestogen dose, interference from endogenous ovarian activity, or, in a minority of cases, endometrial pathology.

On continuous combined HRT, some irregular spotting or breakthrough bleeding is common in the first three to six months as the endometrium stabilises. This is expected in women who recently transitioned from sequential HRT or who are in the early postmenopausal period. Irregular bleeding that begins or continues after six months should be evaluated; the same applies to any bleeding in a woman who has been on continuous combined HRT for more than 12 months and previously had no bleeding.[2]

When to Switch From Sequential to Continuous

The appropriate time to switch is typically when periods have been absent for 12 months, confirming postmenopausal status. In practice, on sequential HRT the monthly withdrawal bleed may continue even when the woman would be postmenopausal without HRT, making this timeline harder to track. Clinical guidance suggests considering the switch based on age (the majority of women have completed menopause by the mid-50s) or when withdrawal bleeds become very light, short, or absent, suggesting the endometrium is no longer responding to progestogen withdrawal.

Some women choose to switch earlier for quality of life reasons: the monthly bleed on sequential HRT becomes burdensome. This is reasonable, but switching while still perimenopausal increases the likelihood of unpredictable breakthrough bleeding on continuous combined.[2]

Progestogen Options Within Each Regimen

The choice of progestogen matters independently of the regimen structure. Micronized progesterone (Utrogestan, Prometrium) has a better tolerability profile than synthetic progestins for most women, including better effects on sleep (its mild sedative effect is a practical advantage for evening dosing) and a potentially lower breast cancer risk with prolonged use (based on observational data from studies such as E3N and ESTHER; this differential risk has not been confirmed in randomised controlled trials and NICE 2023 notes the evidence remains observational).

The levonorgestrel-releasing intrauterine system (Mirena IUS) is also endorsed by NICE 2023 as a licensed method of endometrial protection within HRT regimens, offering a localised progestogen option for women who prefer it. In sequential HRT, micronized progesterone is taken for 12 days each month. In continuous combined HRT, it is taken daily at a lower dose than in the sequential phase. Synthetic progestins (norethisterone, medroxyprogesterone acetate, dydrogesterone) remain appropriate for women who cannot tolerate or access micronized progesterone.

Regimen Comparison

Any unexpected bleeding (including irregular spotting that persists beyond six months on continuous combined HRT, or breakthrough bleeding outside the withdrawal window on sequential HRT) should prompt a clinical review to rule out endometrial pathology.

References

[1] Dempsey, M., Freedman, M. (2019). Hormone therapy for first-line management of menopausal symptoms: Practical recommendations. Obstetrics and Gynecology Clinics of North America, 46(3), 541-554. https://pmc.ncbi.nlm.nih.gov/articles/PMC6683316/

[2] Hormone Replacement Therapy overview. StatPearls. National Library of Medicine. https://www.ncbi.nlm.nih.gov/books/NBK493191/