Key Takeaways: Norethisterone Side Effects

Common side effects: Headache, nausea, breast tenderness, mood changes, irregular bleeding.
Onset: Most start within the first few days of treatment.
Duration: Usually last as long as you take the medication; some may persist briefly after stopping.
Serious side effects: Blood clots, allergic reactions, jaundice – require immediate medical attention.
Contraindications: Pregnancy, blood clot history, liver disease, unexplained bleeding.
Interactions: Some antibiotics, epilepsy drugs, St John's wort can reduce effectiveness.

Norethisterone is generally well tolerated, but like all medicines, it can cause side effects. This guide explains what to expect, when, and for how long – based on the official patient information leaflet and clinical sources.

Important Medical Advice

Stop norethisterone and seek immediate medical help if you experience: sudden shortness of breath, chest pain, coughing up blood, painful swelling in one leg (possible blood clot); severe allergic reaction with facial swelling; yellowing of skin or eyes (jaundice); severe headache or vision problems.

What Are the Common Side Effects of Norethisterone?

The PIL lists side effects that affect different body systems. They range from very common (affecting more than 1 in 10 women) to rare.

Very Common / Common Side Effects

Reproductive system: Breakthrough bleeding, spotting, changes in periods, breast pain or tenderness.
Nervous system: Headache, dizziness, depression, mood swings, tiredness.
Stomach and intestines: Nausea, vomiting, bloating, changes in appetite.
Skin: Acne, hair growth or loss, rash, itching.
Metabolism: Weight gain, fluid retention (swollen ankles).

Less Common but Important Side Effects

Changes in libido, difficulty sleeping, confusion.
Visual disturbances, raised blood pressure.
Liver function changes, jaundice (rare).
Blood clots (thrombosis) – see emergency note.

🗒️ Note: This is not a full list. Always read the PIL inside your medicine pack.

When Do Norethisterone Side Effects Start?

The onset of side effects varies depending on the type:

Side Effect Type	Typical Onset
Nausea, headache, dizziness	Within hours to 1-2 days of first dose
Breast tenderness, mood changes	Usually within the first week
Breakthrough bleeding or spotting	Can occur at any time, more common after several days of use
Skin reactions (acne, rash)	May take a week or more to appear
Blood clot symptoms (rare)	Can occur suddenly, at any time during treatment

Most women tolerate norethisterone well. If side effects are mild, they often settle as your body adjusts. If they persist or worsen, consult your doctor.

How Long Do Norethisterone Side Effects Last?

The duration depends on the side effect and whether you continue the medication.

While taking norethisterone: Most side effects (like nausea, breast tenderness) may persist for the duration of treatment but often lessen after the first few days. If they don't improve, your doctor may adjust the dose or suggest an alternative.
After stopping: Hormonal effects (like menstrual changes) usually resolve within a few days to weeks. Withdrawal bleeding occurs 2-3 days after stopping. Other effects like mood changes typically disappear once the drug clears your system (about 2 days).
Serious side effects: Blood clots require long-term management; jaundice may need further investigation.

If you experience any side effect that doesn't go away after stopping treatment, speak to your GP.

Norethisterone Side Effects Timeline

A visual guide to when you might experience side effects:

Day 1-3: Nausea, headache, dizziness, fatigue – these are often temporary.
Day 4-7: Breast tenderness, mood swings, appetite changes may appear.
Week 2 onwards: Breakthrough bleeding or spotting possible, especially if you miss doses. Acne or skin changes may develop.
After stopping: Withdrawal bleed within 2-3 days. Any lingering hormonal symptoms usually resolve within a week.

Serious side effects like blood clots can occur at any time – be alert for warning signs throughout treatment.

Contraindications: Who Should Not Take Norethisterone?

Based on the PIL, do NOT take norethisterone if any of the following apply:

Allergy to norethisterone or any tablet ingredient.
Pregnancy or suspected pregnancy.
Unexplained vaginal bleeding (not a period).
Current or past blood clot in a vein (DVT) or lung (pulmonary embolism).
History of heart attack or angina.
Severe liver disease, liver tumour, or jaundice during a previous pregnancy.
Porphyria (a rare inherited blood disorder).
Breast or genital cancer (unless specifically prescribed for breast cancer).

Use with caution – discuss with your doctor

Epilepsy, migraine, asthma, kidney disease.
High blood pressure, diabetes, or high cholesterol.
History of depression.
Smoking and age over 35 (increases clot risk).
Immobility after surgery or injury.

Food Interactions and Other Medicines

Food and drink

Norethisterone can be taken with or without food. If you experience nausea, taking it with a meal may help. Avoid grapefruit juice – it can affect the enzyme (CYP3A4) that breaks down norethisterone, potentially altering its levels.

Alcohol in moderation is unlikely to cause problems, but excessive drinking may affect liver function and increase the risk of side effects like dizziness.

Medicine interactions

The following medicines can reduce norethisterone's effectiveness or increase side effects:

Medicine Type	Effect
Epilepsy drugs (phenytoin, carbamazepine)	Reduce norethisterone levels, which may make it less effective.
Antibiotics (rifampicin, rifabutin)	Speed up metabolism, reducing the medicine's effectiveness.
HIV treatments (ritonavir, nelfinavir)	May increase or decrease norethisterone levels.
St John's wort (herbal remedy)	Reduces effectiveness and may cause breakthrough bleeding.
Ciclosporin (immunosuppressant)	May increase ciclosporin levels.
Anticoagulants (warfarin)	May alter anticoagulant effect; monitoring needed.

Always tell your doctor or pharmacist about all medicines you take, including over-the-counter and herbal products.

Norethisterone Side Effects FAQs

Can norethisterone cause weight gain?

Yes, weight gain is a possible side effect, likely due to fluid retention or increased appetite. It's usually modest and reversible after stopping.

What should I do if I miss a period after stopping norethisterone?

If your period doesn't start within a week of stopping, take a pregnancy test and see your doctor. It could be due to hormonal imbalance or other causes.

Is it safe to take norethisterone long-term?

For endometriosis, it's used for up to 6 months. Longer use increases the risk of side effects like blood clots. Regular check-ups are needed.

Can I drink alcohol while taking norethisterone?

Moderate alcohol is unlikely to cause problems, but heavy drinking may worsen dizziness or liver-related side effects. Stay within recommended limits.