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Norethisterone Synthetic Hormone


Norethisterone is a synthetic hormone made to mimic the hormone progesterone which is produced naturally in the body. It is prescribed as a treatment for abnormal or unexpected bleeding from the uterus, symptoms of PMS, endometriosis, painful or heavy periods or to postpone your period.

How does Norethisterone work?

The hormone progesterone is released during the second half of the menstrual cycle when an egg is released from the ovary. Progesterone prepares the body for pregnancy, maintaining the lining of the womb. When an egg is not fertilized the production of progesterone decreases causing the lining of the womb to break away and your period to occur. If progesterone, or it’s synthetic equivalent Norethisterone, is taken continuously, there is no drop in levels to trigger the shedding of the womb lining and you will not have a period.

Side effects

There are a number of side effects you may possibly experience when taking Norethisterone:-

  • Rise in blood pressure
  • Jaundice (yellowing of skin or whites of the eyes)
  • Migraine-type headaches
  • Itching
  • Abdominal pain
  • Dark brown urine
  • Nausea and vomiting
  • Allergic reaction (skin rash, swelling of face, lips and tongue, difficulty swallowing or breathing)
  • Changes in eyesight, hearing or speech

If you experience any of the above side effects, stop taking Norethisterone and contact your doctor. In the case of a severe allergic reaction, this is a medical emergency, call an ambulance.

Other side effects you may experience: –

  • Breakthrough bleeding
  • Breast pain and tenderness
  • Nausea
  • Tiredness or difficulty sleeping
  • Depression
  • Acne or worsening of existing skin conditions
  • Hair growth (especially on the top lip or chin)
  • Fluid retention, bloating or weight gain
  • Changes in sex drive

If you experience any side effects, whether they are listed here or not, speak to you doctor.

Allergies to Norethisterone

As well as the active substance, Norethisterone, other ingredients in this medication are lactose, maize starch and magnesium stearate.  If you are allergic to any of these ingredients, do not take Norethisterone.

How to use

If you are prescribed Norethisterone, you would normally start taking it 3-4 days before you expect your period to begin.  The prescription will consist of 3 tablets per day which can be taken for up to 20 days, depending on how long you wish to delay your period.  Your period should arrive 2-4 days after you stop taking the medication.  It is important to note that, as with the combined contraceptive pill, Norethisterone is unlikely to be considered suitable if you have a history of blood clots (thrombosis).


As with taking the combined oral contraceptive pill, the risk of developing blood clots in veins and arteries is slightly higher than in those women who don’t. If you have previously been advised that the combined pill is not suitable for you, neither will Norethisterone. Speak to your doctor about these possible risks and be aware that you are at greater risk if: –

  • You smoke
  • You or any of your close family have had blood clots
  • Are overweight
  • Have a blood disorder
  • High blood pressure
  • Suffer from migraines
  • Recently had a baby
  • Have a disorder of blood fat metabolism
  • Diabetes (Norethisterone can produce changes in blood sugar levels)
  • You are off your feet for a long time (due to surgery, injury or illness)
  • Suffer with certain medical conditions such as Systemic Lupus erythematosus, sickle cell, Crohn’s or ulcerative colitis

Signs of a blood clot include: –

  • Migraine (not experienced before or worse than normal)
  • Unusually frequent or severe headaches
  • Changes in eyesight such as loss of or blurred vision
  • Sudden changes in hearing, speech, sense of smell, taste or touch
  • Pain or swelling in your leg
  • Stabbing pain when breathing
  • Coughing for no apparent reason
  • Breathlessness
  • Pain ad tightness in chest
  • Sudden weakness or numbness in one side or part of the body
  • Dizziness or fainting

If you notice any of these signs stop taking Norethisterone and speak to your doctor or call NHS 111 for urgent advice.

When seeking a prescription for Norethiterone, also inform your Doctor if you suffer from or have previously suffered from depression, epilepsy, kidney problems, have an intolerance to some types of sugar, are pregnant or breast feeding, have breast cancer or had it in the past.

Interactions with Other Medications

Inform your doctor of any medication, treatments or supplements you are taking or have recently taken as they may negatively interact with Norethisterone. Some of these treatments are: –

  • Other hormonal products
  • Medicines for epilepsy
  • Some antibiotics
  • St John’s Wort
  • Other medications which can cause fluid retention (e.g. ibuprofen)

Before taking any medication, read the patient information leaflet in full and if you have any concerns, speak to your doctor.