Norethisterone Side Effects: What to Expect After Period Delay Tablets
A UK guide to norethisterone side effects: spotting, headache, nausea, bloating, weight and mood changes, how to manage them, serious warning signs, and what happens when the course ends.
Part of the Period Delay Health Guide.
When to get urgent help: Call 999 or go to A&E if you have signs of a blood clot or stroke while taking norethisterone: pain, swelling or redness in one leg; sudden chest pain or breathlessness; coughing up blood; sudden weakness or numbness on one side of the body, difficulty speaking or a sudden severe headache. Also call 999 for a severe allergic reaction, such as swelling of the face, lips, tongue or throat, wheezing or difficulty breathing. Stop taking it and see a doctor the same day if your skin or eyes turn yellow, you get a migraine for the first time, or you have sudden changes to your vision.
Key fact: spotting or light breakthrough bleeding is one of the most frequently reported side effects of norethisterone 5mg tablets. Headache, nausea and fluid retention are also common. Most side effects are mild and settle after the course ends, but blood clots, although rare, need emergency care.
Get Norethisterone 5mg Online
Prescribed after an online consultation with our GPhC-registered pharmacist independent prescribers, and dispensed from our UK pharmacy in plain packaging.
Get norethisterone 5mg →Most people take norethisterone for period delay without serious problems. This guide covers each side effect, how often it happens where that is known, how to manage it, and when to stop and get help. For who should not take it and drug interactions, see how norethisterone works.
Common side effects
The Primolut N product information gives frequencies for a few side effects. The Norethisterone 5mg tablets leaflet lists others without saying how often they happen, so those are marked “not stated”.
| Side effect | How common | What helps |
|---|---|---|
| Spotting or breakthrough bleeding | Not stated for period-delay courses | Keep taking your tablets at regular times. Contact your prescriber if bleeding is heavy |
| Headache | Common (up to 1 in 10) | Paracetamol and fluids. Stop and see a doctor if you get a migraine for the first time |
| Nausea | Common (up to 1 in 10) | Taking it with a snack may help |
| Fluid retention and bloating | Common (up to 1 in 10) | Usually settles after the course |
| Breast tenderness | Not stated | A supportive bra; settles after stopping |
| Mood changes or low mood | Not stated | Contact your prescriber if you feel low or anxious (see below) |
| Weight gain or appetite changes | Not stated | Usually fluid rather than fat (see below) |
| Acne, rash or itching | Not stated | Usually mild; tell your prescriber if it is troublesome |
| Tiredness, dizziness or difficulty sleeping | Not stated | Usually mild; don’t drive if you feel dizzy |
| Changes in sex drive | Not stated | Temporary |
| Constipation, diarrhoea or vomiting | Not stated | Ask your pharmacist if you are sick soon after a dose |
Night sweats and hot flushes are not listed in the UK product information. If you notice them and they bother you, speak to your prescriber.
Spotting and breakthrough bleeding
Spotting is one of the most frequently reported side effects. It does not usually mean your period has started or that norethisterone has stopped working. Keep taking your tablets at the normal times, as missed or late doses make spotting more likely.
When spotting becomes a concern: if bleeding becomes as heavy as a normal period or heavier, contact your prescriber. Heavy bleeding while taking norethisterone should be reviewed.
Weight gain and bloating
Weight gain, bloating, fluid retention and appetite changes are all listed side effects. With the short courses used for period delay, most people who notice a change find it is fluid rather than fat, and it settles within days of finishing the course. Cutting down on salty food may help with bloating.
Mood changes
Low mood, mood changes or nervousness can happen with progestogens. The Norethisterone 5mg tablets leaflet warns that depression can be serious and may sometimes lead to suicidal thoughts. If you notice mood changes or symptoms of depression, contact a doctor as soon as possible. If you have a history of depression or anxiety, mention it during your consultation.
How long will I bleed after taking norethisterone?
After your last tablet, your period usually starts within 3 days and often lasts about as long as a normal period. Some people find this bleed heavier or longer than usual. If you are planning around an event, our guide on how to take norethisterone covers timing your course.
If your period has not started within 3 days of stopping, take a pregnancy test and speak to your GP or our pharmacist, especially before taking another course. If bleeding is very heavy or lasts more than 10 days, contact your prescriber.
Serious side effects — when to stop
Stop taking norethisterone and call 999 if you have: sudden chest pain or breathlessness · coughing up blood · pain, swelling or redness in one leg · sudden weakness or numbness on one side, difficulty speaking or a sudden severe headache · swelling of the face, lips, tongue or throat, or difficulty breathing. These can be signs of a blood clot, stroke or severe allergic reaction.
Stop taking it and see a doctor the same day if you have:
- Yellowing of the skin or the whites of the eyes (jaundice)
- A migraine-type headache for the first time, or headaches that are much worse than usual
- Sudden changes to your vision
- Very high blood pressure, if you monitor it
Contact your prescriber about heavy vaginal bleeding, severe stomach pain, or a rash.
After stopping
Most side effects settle within a few days of stopping. Your period usually starts within 3 days of your last tablet. If side effects last more than a week after stopping, or your periods don’t return to your usual pattern, speak to your GP or prescriber.
UK safety and prescribing information
- Legal status: norethisterone is a prescription-only medicine (POM). At Access Doctor it is prescribed only after an online consultation with a GPhC-registered pharmacist independent prescriber, who may decline and suggest an alternative or that you see your GP.
- Licence: it is the only progestogen licensed in the UK to delay periods (NHS Specialist Pharmacy Service). The dose is 5mg three times a day, starting 3 days before your period is due.
- Course length: take it for as long as your prescriber advises. The Primolut N licence describes courses of no longer than 10 to 14 days, and NHS Specialist Pharmacy Service guidance says it can be taken for up to 3 to 4 weeks if necessary.
- Not a contraceptive: use condoms or another method while you take it.
- Blood clots: part of each dose is converted in the body to ethinylestradiol, the oestrogen in the combined pill (about 4–6 micrograms for every 1mg, according to the Primolut N product information), so the same blood clot warnings apply. Your prescriber will check risk factors such as a previous clot, smoking, a BMI over 30, being over 35, recent surgery and long-haul travel.
- Pregnancy and breastfeeding: do not take it if you are or might be pregnant. The Primolut N product information says it should be avoided while breastfeeding, so ask your prescriber.
- Reporting side effects: you can report suspected side effects to the MHRA through the Yellow Card scheme website or the Yellow Card app.
Planning to Delay Your Period?
Start your consultation at least a week before your period is due, so your tablets arrive in time to begin 3 days beforehand. Approved orders placed before 3pm Monday to Friday are dispatched that day by Royal Mail Tracked 24.
Get norethisterone 5mg →Frequently asked questions
What are the most common side effects of norethisterone?
Spotting or breakthrough bleeding is one of the most frequently reported side effects. Headache, nausea and fluid retention are common, affecting up to 1 in 10 people. Breast tenderness, bloating, mood changes and acne are also reported.
Does norethisterone cause spotting?
Yes. Spotting or light breakthrough bleeding can happen and does not usually mean the medicine has stopped working. Keep taking your tablets at regular times and contact your prescriber if the bleeding becomes heavy.
Does norethisterone cause weight gain?
Weight gain, bloating and fluid retention are listed side effects. With the short courses used for period delay, most changes are due to fluid and settle within days of finishing the course.
Does norethisterone affect mood?
It can. Some people notice low mood, mood changes or nervousness. The leaflet warns that depression can be serious, so contact a doctor as soon as possible if you notice mood changes or symptoms of depression.
When should I stop taking norethisterone?
Stop and call 999 if you have signs of a blood clot, stroke or severe allergic reaction, such as chest pain, breathlessness, a painful swollen leg, sudden weakness on one side or swelling of the face or throat. Stop and see a doctor the same day if you develop jaundice, a first migraine or sudden vision changes.
How long do norethisterone side effects last?
Most side effects settle within a few days of stopping the course. If they last more than a week after stopping, speak to your GP or prescriber.
Can I drink alcohol while taking norethisterone?
There is no known interaction between norethisterone and alcohol, but alcohol can make nausea and headaches worse. If you are sick soon after a dose, ask your pharmacist for advice. See our guide on norethisterone and alcohol for more.
Does norethisterone affect fertility or future periods?
Norethisterone is used for short courses and is not known to cause long-term problems with fertility. It is not a contraceptive, so use contraception while taking it. If your periods do not return to your usual pattern, speak to your GP.
Can norethisterone cause thrush?
Thrush is not listed as a side effect in the UK product information. If you develop itching, soreness or unusual discharge, speak to a pharmacist, as thrush is easily treated.
Is norethisterone safe?
Norethisterone is a licensed medicine, and whether it is suitable depends on your medical history, which a prescriber checks before it is supplied. Like any medicine it carries risks, particularly blood clots in people with risk factors, which is why it is only supplied after a consultation.
Should norethisterone be taken with food?
The leaflet does not say it must be taken with or without food. If it makes you feel sick, taking it with a snack or meal may help.
What if I have no period after stopping norethisterone?
Your period usually starts within 3 days of your last tablet. If it does not, take a pregnancy test and speak to your GP or pharmacist before taking another course.
Will norethisterone stop bleeding once my period has already started?
No. Norethisterone for period delay needs to be started at least 3 days before your period is due. It does not reliably stop bleeding that has already started.
Can I get pregnant while taking norethisterone?
Yes. Norethisterone is not a contraceptive, so you can still get pregnant while taking it. Use condoms or another method of contraception.
Can I stop taking norethisterone suddenly?
Yes. Stopping simply brings on your period, usually within 3 days. You do not need to reduce the dose gradually for a short course. Tell your prescriber if you are stopping because of side effects.
Does norethisterone cause blood clots?
It can, although this is rare. Part of each dose is converted in the body to an oestrogen, so the same blood clot warnings as the combined pill apply. Prescribers check risk factors such as a previous clot, smoking, a BMI over 30, being over 35 and long-haul travel before prescribing.
References
- electronic Medicines Compendium. Norethisterone 5mg Tablets — Summary of Product Characteristics and Patient Information Leaflet. medicines.org.uk
- electronic Medicines Compendium. Primolut N 5mg Tablets — Summary of Product Characteristics. medicines.org.uk
- NHS Specialist Pharmacy Service. Choosing a medicine to delay periods. 2025. sps.nhs.uk
- NHS. Norethisterone. nhs.uk
- MHRA. Yellow Card scheme. yellowcard.mhra.gov.uk
Medical disclaimer: This article is for information only and does not replace advice from your GP, pharmacist or prescriber. Norethisterone is a prescription-only medicine; always follow the instructions on your label and leaflet. In a medical emergency, call 999.