Period delay tablets usually contain norethisterone, a progestogen. Taking them keeps hormone levels up so the lining of the womb is not shed, delaying your period until you stop.
The point most people miss: this is not contraception. It is a hormone tablet, and it looks like a contraceptive pill, but you are not protected against pregnancy while taking it for this purpose. If you need contraception during that time, arrange it separately.
Timing matters and needs planning. These tablets are started several days before your period is due, not on the day, so leaving it until the last minute means it will not work. Get advice at least a week ahead where possible.
Common hormonal medicine side effects
- Bloating and fluid retention
- Breast tenderness
- Nausea
- Headache
- Mood changes or irritability
- Breakthrough bleeding or spotting while taking them
- Reduced sexual desire, and tiredness
Effects are usually mild for a short course and stop once you finish. There is a certain irony worth flagging: bloating and breast tenderness are the symptoms some people were hoping to avoid by delaying the period in the first place.
Bleeding, mood, skin, weight and cycle changes
Your period normally starts two to three days after the last tablet, though this varies. Spotting while taking them does not necessarily mean they are not working, and is more likely if you started later than advised.
The next cycle may be different from usual before settling back, and the period after may be heavier or lighter than normal. See bleeding after the period delay pill and a missed period after norethisterone.
Serious warning signs that need medical attention
Get emergency help for:
- Pain, swelling or redness in one calf or thigh
- Sudden breathlessness or chest pain
- Sudden severe headache, one-sided weakness, difficulty speaking, or loss of vision
- Yellowing of the eyes or skin
See hormonal medicine and blood clot symptoms. Also contact a doctor for very heavy bleeding or severe abdominal pain.
Who may be at higher risk?
Tell your doctor or pharmacist about a personal or family history of blood clots, liver conditions, migraine with aura, a history of breast cancer, current or possible pregnancy, or unexplained vaginal bleeding not yet investigated.
Long-haul travel around the same time is worth mentioning, since immobility is itself a clot risk factor.
If you are using this repeatedly, for example every month or before every event, that is worth reviewing. There are other ways to control when periods happen, including some contraceptive methods used continuously, which may suit better than repeated short courses.
What to discuss with your doctor, pharmacist or clinic
- When exactly should I start and stop for the dates I need?
- Do I need contraception as well?
- Is it safe for me given my history and any travel?
- When should my period arrive afterwards?
- If I want to do this regularly, is there a better option?
Related contraception, HRT and hormonal medicine guides
- Hormonal medicine side effects
- Women’s health and hormonal medicine side effects
- Progesterone tablets side effects
- When to see a doctor about hormonal medicine
- Report a hormonal medicine side effect
See also norethisterone side effects and Primolut N.
Medical Disclaimer: This content is for informational and educational purposes only and does not constitute medical diagnosis, prescription, or professional advice. Always read the patient information leaflet and consult a qualified doctor or pharmacist regarding any medicine or health concern.