Norethisterone 5mg Tablets

What is Norethisterone?

Norethisterone is a synthetic progesterone used to delay a period. It is useful for when you may want to delay your period to a later date to stop it from occurring at an inconvenient time, for example on your wedding day or on a holiday.

How does it work?

A period is triggered by a drop in progesterone levels during a woman’s menstrual cycle. Norethisterone works by artificially maintaining a woman’s progesterone levels which prevents triggering a period.

When do I need to take it?

Norethisterone treatment should be started three days before you expect your period to begin. It must be taken three times a day for as long as you want to delay your period. You can delay your period for a maximum of 27 days. To restart your menstrual cycle you should stop taking the treatment day or two before you want to have your period.

Norethisterone should not be used more regularly than every four months. 

Norethisterone is not a contraceptive and should not be used as one. It will not stop you from becoming pregnant. If you are concerned about this you should speak to your GP.

Pregnancy and Breastfeeding?

Norethisterone alters your hormone levels. If you are pregnant or breastfeeding you should not take Norethisterone.

 P.S. 2019

Norethisterone 5mg tablets are to be taken three times a day to delay periods. The course should be started 4 to 5 days before a period is due and continued for as long as needed. A period bleed will normally start within 2 to 3 days of stopping the medication.

Women currently taking a contraceptive pill (both combined and progestrogen only) should not use norethisterone to delay their periods. Information about delaying periods whilst taking contraceptive pills or with Norethisterone can be found on the NHS Choices page How can I delay my period?.

If you forget to take the tablets

Do not take a double dose to make up for a forgotten dose. If you forget to take a dose take it as soon as you remember it and then take the next dose at the right time.

The most commonly reported side effects are bloating, breast tenderness, loss of libido, and stomach pains. Side effects are more likely if norethisterone is taken long term, rather than in a short course to delay periods.

Some women taking norethisterone experience fluid retention which can worsen a pre-existing migraine, epilepsy, blood pressure and asthma.

Very rarely, norethisterone may cause a severe allergic reaction which can in some cases be life-threatening. Sudden onset of some or all of the following require emergency treatment (very rare):

• wheezing
• difficulty breathing
• feeling faint
• swelling of the face or tongue
• swelling of the hands and feet
• intense itchy skin rash

Find out more on the patient information leaflet

Increased risk of clotting

All women have a small chance of having a blood clot in the veins of the legs or in the lungs or other parts of the body. The risk of a having a clot is very slightly increased when taking norethisterone. The risk of having a clot is also increased with the folloing risk factors:

• if the patient is very overweight
• if they have a history of previous blood clot in the veins or lungs
• if there is a family history of blood clots
• if the patient is immobilie for long periods of time, for example post surgery or if they have a physical disability.
• if the patient has just had a serious injury or any major invasive surgery.
• if the patient has a history of repeated miscarriage

INTERACTIONS with other medicines

Patients should check with their doctors before taking norethisterone if taking any of the following. 

• Medicines to treat epilepsy (e.g. phenytoin, carbamazepine)
• Antibiotic medicines to treat an infection (e.g. tetracyclines, rifampicin, co-trimoxazole)
• Antiviral medicines to treat HIV (e.g. ritonavir, nelfinavir)
• Anticancer medicines
• Herbal preparations containing St Johns Wort (Hypericum perforatum)
• Aminoglutethimide, sometimes used in Cushings syndrome
• Ciclosporin (for suppressing the immune system)
• Non-steroidal inflammatory drugs (NSAIDs) for treating pain and inflammation
• Medicines for high blood pressure