Part of our complete guide to periods in the UK.
Norethisterone Side Effects: What to Expect After Period Delay Tablets
A UK clinical guide to norethisterone side effects — common effects such as spotting, breast tenderness, nausea and mood changes, how to manage them, serious warning signs, and what happens when the course ends.
▶ What are the side effects of norethisterone?
Common norethisterone side effects include breast tenderness, bloating, nausea, headache, mood changes and light spotting (in ~1 in 10 women). Most are mild and resolve after stopping. Seek emergency care for chest pain, breathlessness, sudden severe headache, or severe leg pain — these may indicate a blood clot.
Most women tolerate norethisterone well for the short courses used in period delay. Side effects tend to be mild and temporary — resolving when the course ends. This guide covers each side effect, how common it is, how to manage it, and when to stop and seek medical advice. For dosing and contraindications, see: Norethisterone complete guide.
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Get Norethisterone →Common Side Effects
| Side effect | How common | Management |
|---|---|---|
| Breast tenderness or swelling | Common | Supportive bra; resolves after stopping |
| Bloating and fluid retention | Common | Mild — resolves after stopping; reduce salt intake |
| Nausea | Common (first few days) | Take with food; usually settles after day 2-3 |
| Headache | Common | Paracetamol; ensure adequate hydration |
| Mood changes (low mood, irritability) | Common | Usually mild; resolves after stopping. Contact prescriber if severe. |
| Light spotting / breakthrough bleeding | Common (~1 in 10) | Continue taking tablets; this is normal. Contact prescriber if heavy. |
| Reduced libido | Uncommon | Temporary; resolves after stopping |
| Skin changes or acne | Uncommon with short-course use | Usually mild; resolves after stopping |
Understanding Spotting and Breakthrough Bleeding
Around 1 in 10 women experience light spotting while taking norethisterone. This is one of the most common concerns — but it does not mean the medication has failed or that your period has started. Light spotting while taking norethisterone is a known side effect, not a treatment failure. Continue taking the tablets at the normal dose and schedule.
When spotting becomes a concern: If bleeding becomes heavy (comparable to a normal period or heavier), contact your prescriber. Heavy bleeding while taking norethisterone warrants clinical review — it may indicate that the dose is insufficient or that something else needs investigation.
Weight Gain and Bloating
True weight gain from a short course of norethisterone (10-14 days for period delay) is uncommon. What most women experience is mild fluid retention and bloating — a sensation of fullness or heaviness — which is progesterone-related and resolves within days of stopping. Avoiding excess salt and staying well hydrated helps manage bloating during the course.
Mood Changes
Low mood, irritability, or mild anxiety affect some women taking norethisterone. This is a recognised progestogen effect and is usually mild and short-lived. If you have a history of depression or anxiety, mention this during your consultation — your prescriber will weigh this up when deciding whether to prescribe. If mood changes feel significant while taking norethisterone, contact your prescriber rather than stopping abruptly.
Serious Side Effects — When to Stop Immediately
Stop norethisterone immediately and call 999 if you experience: sudden chest pain or tightness · breathlessness · coughing up blood · sudden severe headache · severe leg pain, redness or swelling · sudden visual disturbance. These could indicate a blood clot (DVT or pulmonary embolism) and require immediate emergency assessment.
Also stop and contact your prescriber (rather than 999, unless severe) if you develop:
- Jaundice (yellowing of skin or whites of eyes)
- Severe abdominal pain
- Heavy vaginal bleeding
- Severe, persistent headache or migraine
- Signs of allergic reaction (rash, facial swelling, difficulty swallowing)
Side Effects After Stopping
Once you stop taking norethisterone, side effects typically resolve within a few days. Your period will arrive within 2-3 days of taking the last tablet, and may be slightly heavier or longer than usual as the uterine lining sheds. This is expected. Your cycle should return to normal within 1-2 cycles. If any side effects persist for more than a week after stopping, speak to your GP or prescriber.
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View Period Delay Treatment →Frequently Asked Questions
What are the most common side effects of norethisterone?
The most common side effects are breast tenderness or swelling, bloating and fluid retention, nausea (particularly in the first few days), headache, mood changes including low mood or irritability, and light spotting or breakthrough bleeding in around 1 in 10 women.
Does norethisterone cause spotting?
Yes, around 1 in 10 women experience light spotting or breakthrough bleeding while taking norethisterone. This does not mean the medication has failed and is not a reason to stop. If bleeding becomes heavy, contact your prescriber.
Does norethisterone cause weight gain?
Weight gain is listed as a possible side effect, but it is uncommon with the short courses used for period delay (typically 10-14 days). Most women notice mild fluid retention and bloating rather than true weight gain, which resolves once the course ends.
Does norethisterone affect mood?
Some women experience mood changes including low mood, irritability, or anxiety. These are generally mild and resolve when the course ends. If mood changes are severe, contact your prescriber.
When should I stop taking norethisterone?
Stop immediately and seek medical advice if you experience sudden chest pain, breathlessness, severe leg pain or swelling, or sudden severe headache — these could indicate a blood clot. Also stop and contact your prescriber if you develop jaundice, severe abdominal pain, or heavy vaginal bleeding.
How long do side effects last?
Side effects from norethisterone typically resolve within a few days of stopping the course. They are not permanent. If side effects persist beyond a week after stopping, speak to your prescriber.
References
- MHRA. SPC: Norethisterone 5mg tablets. 2024. medicines.org.uk/emc
- NHS. Norethisterone — side effects. nhs.uk/medicines/norethisterone/side-effects
- NICE. Norethisterone: CKS. 2024. cks.nice.org.uk
Medical disclaimer: This article is for informational purposes only. Norethisterone is a prescription-only medicine in the UK. A clinical consultation is required before it can be dispensed. In a medical emergency, call 999.