Microgynon is a combined oral contraceptive pill used primarily to prevent pregnancy. Each tablet contains two synthetic hormones: 30 micrograms of ethinylestradiol (a synthetic estrogen) and 150 micrograms of levonorgestrel (a synthetic progestogen). Beyond contraception, it is also prescribed to manage heavy or painful periods and to help control symptoms of endometriosis.
How Microgynon Prevents Pregnancy
Microgynon works through three separate mechanisms that reinforce each other. First, it stops your ovaries from releasing an egg each month by suppressing the hormonal surge that triggers ovulation. Second, it thickens the mucus at the entrance to the womb, creating a physical barrier that makes it harder for sperm to reach an egg. Third, it thins the lining of the womb so that, in the unlikely event an egg is fertilized, it would have difficulty implanting.
When taken perfectly, meaning at the same time every day without missing a dose, the combined pill has a failure rate of just 0.3% in the first year. In real-world use, where people occasionally forget a pill or take it late, effectiveness drops to about 91%, with roughly 9 in 100 users experiencing an unintended pregnancy over a year. The gap between those two numbers highlights how much consistency matters.
Uses Beyond Contraception
Many people are prescribed Microgynon not just to prevent pregnancy but to manage menstrual problems. Because the hormones thin the womb lining, it can significantly reduce the volume and duration of heavy periods and ease menstrual cramps. Some people also find that their periods become more predictable on the pill, which can be helpful for planning around symptoms.
Combined hormonal contraceptives like Microgynon are considered a first-line treatment for endometriosis symptoms. Endometriosis involves tissue similar to the womb lining growing outside the uterus, causing pain that often worsens during periods. By suppressing estrogen production and thinning the uterine lining, Microgynon can slow the growth of this tissue and reduce pain. Some people take it continuously (skipping the break between packs) to avoid withdrawal bleeds altogether, which can offer even better symptom control.
How to Take It
Microgynon comes in 21-day packs. You take one active tablet daily for 21 consecutive days, then have a 7-day break during which you take no pills. During the break, you will typically have a withdrawal bleed that resembles a period. You start the next pack after the 7 days are up, whether or not the bleeding has stopped. Some versions (like Microgynon 30 ED) include 7 inactive “dummy” tablets for the break week so you stay in the habit of taking a pill every day.
Timing matters. Taking your pill at roughly the same time each day keeps hormone levels steady and maximizes effectiveness. If you miss a pill by more than 24 hours, your protection against pregnancy may be reduced, and you may need to use additional contraception temporarily depending on where you are in the pack.
Common Side Effects
Breakthrough bleeding or spotting between periods is one of the most common side effects, particularly in the first two to three months as your body adjusts. This usually settles on its own. Some people report headaches, nausea, breast tenderness, or dizziness, though evidence linking these directly to the pill rather than other causes is limited. A small number of users develop slightly elevated blood pressure, so this is typically monitored during check-ups.
Mood changes and changes in sex drive are frequently mentioned by users. Weight fluctuation is another common concern, though studies have not consistently shown that the combined pill causes significant weight gain.
Serious Risks
The most significant rare risk is blood clots. Combined hormonal contraceptives increase the chance of a clot forming in a deep vein (usually in the leg) or travelling to the lungs. This affects up to 1 in 1,000 users per year, which is low but not negligible. Signs to watch for include unusual swelling, redness, or pain in one leg, sudden shortness of breath, or chest pain.
A clot can also, in rare cases, cause a heart attack or stroke. The risk is higher if you smoke (especially if you’re over 35), have high blood pressure, or have a personal or family history of clotting disorders. Long-term use of the combined pill is also associated with a small increase in the risk of breast cancer and cervical cancer, though these risks decrease after stopping the pill.
Who Should Not Take Microgynon
Certain health conditions make combined hormonal contraceptives unsafe. You should not take Microgynon if you:
- Have a history of blood clots, stroke, or heart attack
- Have a known clotting disorder such as Factor V Leiden
- Experience migraines with aura
- Have severely high blood pressure (generally 160/100 or above) or blood pressure-related vascular disease
- Have current breast cancer
- Have serious liver disease, including liver tumours or decompensated cirrhosis
- Are a smoker aged 35 or older who smokes 15 or more cigarettes a day
- Are in the first 21 days after giving birth, whether breastfeeding or not
- Have lupus with certain antibody markers that raise clotting risk
Major surgery requiring prolonged bed rest is also a reason to stop the pill temporarily, because immobility combined with the hormonal effects further raises the clot risk. Your prescriber will typically review your full medical history before starting Microgynon.
Medications That Reduce Effectiveness
Certain drugs speed up how quickly your liver breaks down the hormones in Microgynon, potentially making it less effective. These are known as enzyme-inducing medications and include some treatments for epilepsy, HIV, and tuberculosis. The herbal supplement St John’s Wort, commonly used for low mood, has the same effect. Some antibiotics, particularly rifampicin, are also well-known to interfere with the pill. If you’re prescribed any new medication, it’s worth checking whether it could affect your contraception so you can use backup methods if needed.