Primolut N contains norethisterone 5 mg, a progestogen hormone. It is used to delay a period, treat heavy or painful periods, irregular bleeding and endometriosis. It is not a contraceptive and does not prevent pregnancy at this dose.

What is Primolut N?

Primolut N contains norethisterone 5 mg, a synthetic progestogen — a hormone similar to the progesterone the body produces naturally. It is a Schedule 4 prescription medicine.

The menstrual cycle is driven by two hormones. Oestrogen builds up the endometrium, the lining of the womb, in the first half of the cycle. Progesterone maintains that lining in the second half. When progesterone falls at the end of the cycle, the lining is shed — that is a period.

Norethisterone works by keeping progesterone activity high. As long as you take it, the lining is maintained and not shed, so bleeding does not start. Stop the tablets and the level falls, which triggers a period two to three days later.

That single mechanism explains all of its uses: it postpones a period, it settles heavy or erratic bleeding by stabilising the lining, and it suppresses the hormonal cycling that drives endometriosis.

It is not a contraceptive. This is the most important thing to be clear about. At this dose norethisterone does not reliably prevent ovulation, so you can still become pregnant while taking it. Progestogen-only contraceptive pills contain a different, much smaller dose designed for that purpose, and they are not interchangeable. Continue your usual contraception.

What is Primolut N commonly used for?

Delaying or postponing a period, for a holiday, an examination, a wedding, a competition or a religious observance. This is its best-known use.
Heavy menstrual bleeding (menorrhagia).
Painful periods (dysmenorrhoea).
Irregular or unpredictable bleeding.
Breakthrough bleeding, including on hormonal contraception.
Endometriosis, to suppress the cycle and reduce pain.
Premenstrual symptoms, in some cases.
Stopping abnormal uterine bleeding, under medical direction.

To delay a period, it is started a few days before the period is due and continued until you want bleeding to begin — your prescriber will tell you exactly when to start and stop. Bleeding usually follows two to three days after the last tablet. Timing is what makes it work, so get the instruction clear before you need it.

For heavy or irregular bleeding, the cause matters. Heavy periods can be due to fibroids, polyps, adenomyosis, a bleeding disorder, thyroid disease, or — importantly — endometrial changes that need investigating. Norethisterone controls the bleeding; it does not identify why it is happening.

Bleeding that needs assessment rather than just treatment includes bleeding between periods, bleeding after sex, any bleeding after the menopause, periods that have suddenly become much heavier, or heavy bleeding with pain or dizziness.

How Primolut N fits into this medicine category

Group	Examples	Role
Progestogens	Norethisterone (Primolut N), medroxyprogesterone	Cycle control, heavy bleeding, endometriosis
Combined hormonal contraceptives	Combined pill, patch, ring	Contraception; also regulate periods
Progestogen-only contraceptives	Mini-pill, injection, implant, hormonal IUD	Contraception; often reduce bleeding
Non-hormonal options for heavy bleeding	Tranexamic acid (Tranic), NSAIDs	Reduce bleeding and pain without hormones
Anti-inflammatories	Ibuprofen, diclofenac	Period pain

For heavy bleeding without a hormonal aim, tranexamic acid taken only during the period is a well-evidenced non-hormonal alternative worth asking about. See the sexual health and urology medicines hub.

What to check before using Primolut N

Continue your usual contraception. Primolut N does not prevent pregnancy.

Get the timing instruction clear, particularly for delaying a period — when to start, how long to continue, and when bleeding should follow.

Do not take it if you might be pregnant. Take a test if there is any doubt.

Tell your prescriber or pharmacist if you:

Have had a blood clot — a DVT or pulmonary embolism — or have a clotting disorder or a family history of clots.
Have had a stroke, heart attack or have heart disease.
Smoke, particularly if over 35.
Have liver disease, or a history of jaundice in pregnancy.
Have breast cancer or a history of it, or another hormone-sensitive cancer.
Have migraine with aura.
Have diabetes, high blood pressure or high cholesterol.
Are pregnant or breastfeeding.
Have undiagnosed vaginal bleeding — this needs assessment before hormonal treatment.
Take rifampicin, carbamazepine, phenytoin, St John’s wort or an HIV medicine, which can reduce its effect.
Are due surgery or a long period of immobility.

Follow the dispensing label. This page does not set doses, and the schedule differs entirely between delaying a period and treating heavy bleeding.

Possible cautions and when to ask a pharmacist or doctor

Blood clot risk. Progestogens at this dose carry a small increased risk of venous thromboembolism. It is small in an otherwise healthy person, but it is the reason for the clotting questions above, and it rises with smoking, obesity, immobility and age.

Common effects include breast tenderness, headache, nausea, bloating, mood changes, acne and breakthrough spotting. Most settle.

Breakthrough bleeding while taking it can happen, particularly if doses are missed. Take it at the same times each day.

Do not use it repeatedly to suppress periods long term without medical review. If you find yourself wanting to delay periods often, or if periods are heavy enough to disrupt life regularly, there are better long-term options — including hormonal contraception or a hormonal IUD, which many people find suits them better.

Get persistent abnormal bleeding investigated, rather than repeatedly controlling it.

Seek urgent medical attention for pain, swelling, warmth or redness in one leg; sudden breathlessness or chest pain; coughing up blood; a sudden severe headache, visual disturbance, one-sided weakness or slurred speech; yellowing of the skin or eyes; or severe abdominal pain. Seek assessment for any bleeding after the menopause, bleeding between periods or after sex, or heavy bleeding with dizziness or breathlessness.

Related medicine guides

Frequently asked questions

What is Primolut N used for? Delaying a period, and treating heavy, painful or irregular periods and endometriosis. It contains norethisterone 5 mg.

Is it a contraceptive? No. At this dose it does not reliably prevent ovulation, so you can still become pregnant. Continue your usual contraception.

How do I use it to delay my period? It is started a few days before the period is due and continued until you want bleeding to begin. Get the exact timing from your prescriber.

When will my period come after stopping? Usually two to three days after the last tablet.

Can I take it every month? Not without review. Repeated use to suppress periods warrants a discussion about better long-term options.

Are there non-hormonal options for heavy periods? Yes. Tranexamic acid taken during the period, and anti-inflammatories, both reduce bleeding without hormones.

What Is Primolut N Used For?