Period Delay Facts: Everything You Need to Know About Norethisterone

Period delay tablets — also known as period delay pills or period delay medication — offer women a safe, effective, and clinically proven way to postpone menstruation for important events, holidays, and personal reasons. The most widely used period delay medication in the UK is norethisterone 5mg, a synthetic form of the hormone progesterone. This guide covers everything you need to know — how norethisterone works, how to take it, its effectiveness, side effects, and how to access it.

What Is Norethisterone?

Norethisterone is a synthetic progestogen — a synthetic version of the naturally occurring female sex hormone progesterone. It belongs to the class of medicines called progestogens and has been used in the UK for decades for a variety of menstrual and gynaecological conditions.

In normal menstrual physiology, a drop in progesterone levels towards the end of the menstrual cycle signals the uterine lining to shed — this is what we call a period. By taking norethisterone, you maintain artificially elevated progesterone levels, preventing this signal and delaying your period for as long as you continue taking the tablets.

How Does Norethisterone Work for Period Delay?

How to Take Norethisterone: Dosage Guide

Conditions Norethisterone Treats Beyond Period Delay

• Heavy periods (menorrhagia) — norethisterone can reduce blood flow and shorten period duration
• Painful periods (dysmenorrhoea) — by regulating hormonal fluctuations and uterine contractions
• Endometriosis — daily norethisterone suppresses endometrial growth
• Premenstrual syndrome (PMS) — taken during the luteal phase to stabilise hormone levels
• Progesterone deficiency

Side Effects of Norethisterone

• Acne or skin changes
• Low mood or mood changes
• Fluid retention and bloating
• Breast tenderness
• Reduced libido
• Nausea or headaches
• Light spotting or breakthrough bleeding (in ~10% of women)

Who Should Not Take Norethisterone?

• Pregnant women or those who may be pregnant
• Women who are breastfeeding
• Women with a personal history of blood clots (VTE, PE)
• Women with severe liver disease
• Women with a history of hormone-sensitive cancer
• Women with unexplained vaginal bleeding

Alternatives to Norethisterone for Period Delay

For women who cannot take norethisterone or who need longer-term cycle control, alternatives include:

• Combined oral contraceptive pill (COC) — taking active pills continuously skips withdrawal bleeds and provides contraceptive cover
• Progesterone-only pill (mini pill) taken continuously
• Hormonal IUD (Mirena) — reduces or stops periods long-term
• Depo-Provera injection — often reduces or stops periods

For more detail on these alternatives and the full norethisterone guide, see our articles on A Guide to Norethisterone and Can You Delay Your Period?.