Mercilon

Mercilon is an effective combined contraceptive pill which contains progestogen and oestrogen.

Pack of 63 Mercilon 150/20µg desogestrel/ethinylestradiol tablets
Plastic wrapped blister pack of Mercilon pills
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6 x 21 tablet(s) - £28.00

3 x 21 tablet(s) - £20.00


What is Mercilon?

Mercilon is a combined contraceptive pill. There are 2 types of contraceptive pills available: combined and progesterone-only. The combined pill contains synthetic forms of two sex hormones found in your body.

Mercilon contains desogestrel, a type of progestogen, and ethinylestradiol, a type of oestrogen. You can take Mercilon for 21 days after which you will have a 7 day pill free break. During this break, you’ll usually have some withdrawal bleeding. This should be lighter than your normal period.

How to take Mercilon

Taking Mercilon is straightforward! All you need to do is take a pill around the same time each day for 21 days.

On the back of the blister strip, you’ll see the days of the week printed on the foil. Start taking Mercilon on the day of the week it is and follow the arrows around until you complete all 21 pills. The arrows will also help you to remember if you forget to take a pill.

After finishing a strip of pills, you’ll have a 7 day pill free break. You should start your next strip of pills on the eighth day. You may have some light bleeding during this week but you should still start the next cycle of pills on time even if you have not finished bleeding.

You’ll have contraceptive protection during this 7 day break if you remember to start your next pack on time. You do not need to use extra contraception during this week.

You can set a reminder to take your pill on your phone or keep your packet of pills somewhere easy for you to access.

If you forget to take a pill, check when you were supposed to take it. If it’s less than 24 hours ago, take your pill as soon as you remember. You’ll still have contraceptive protection and can continue taking the rest of the pills as normal.

If it’s been more than 24 hours since you were due to take a pill or you’ve missed more than 1 pill, take the most recent pill as soon as you remember. This might mean taking 2 pills on the same day. You should then use extra contraception for the next 7 days, like condoms.

Then, if there are 7 pills or more left on your strip of pills, continue taking them as normal. But, if there are less than 7 pills left, take them as usual and skip the usual 7 day break by starting the next strip of pills straight away.

If you missed two or more pills and you’ve had unprotected sex during the 7 days before, there’s a chance you can become pregnant. In this case, you may need to use emergency contraception like the morning after pill.

You may need to do a pregnancy test if you’ve missed 2 or more pills.

For more information about what to do if you’ve missed a pill, read the patient information leaflet.

How does Mercilon work?

Mercilon provides contraceptive protection in a few different ways. The most important of these is preventing your ovaries from releasing an egg, also known as ovulation.

Each month, the hormones that control your menstrual cycle need to be at a certain level to trigger ovulation. When you take Mercilon, you’re keeping these hormones from reaching that level. This way, you prevent ovulation from happening.

If you forget to take a pill or vomit after you have taken a pill, your hormone levels may start to return to normal.

Mercilon also prevents pregnancy by thickening the fluid your cervix produces so that sperm cannot get into your womb.

How effective is Mercilon?

If you take Mercilon perfectly, it is 99% effective in preventing pregnancy. But we all know we might miss a pill here and there! With typical use, Mercilon is around 91% effective. If you use extra contraception around the times that you miss a pill, you’ll have a very low risk of becoming pregnant.

If you start taking Mercilon on the first 5 days of your period, you’ll have contraceptive protection straight away. If you start taking Mercilon at any other time, use extra contraception, such as condoms, for the first 7 days.

Remember that Mercilon does not protect you against sexually transmitted infections (STIs). Only condoms can protect you against STIs as they create a physical barrier between the infected person and you.

What are the side effects of Mercilon?

You may experience side effects when taking Mercilon, but not everyone gets them. Most side effects are temporary and will disappear as your body gets used to taking the medication.

Common side effects can occur when you start taking Mercilon. It might take a few days or weeks for you to feel better. Some common side effects of Mercilon include:

  • mood changes
  • headache
  • weight gain
  • sore breasts
  • feeling sick

Uncommon side effects usually happen in less than 1 in 100 women. Some uncommon side effects might occur over a longer period of time, like having skin problems.

The uncommon side effects of Mercilon include:

  • migraine
  • fluid retention
  • less interest in sex drive
  • vomiting
  • diarrhoea
  • breast enlargement
  • skin rashes

If you get a migraine for the first time after taking Mercilon or find that the migraine is worse than usual, speak to your doctor immediately.

Mercilon can slightly increase your risk of blood clots. This risk is still very low and may only happen to a small number of women.

If you notice any of these symptoms of a blood clot after taking Mercilon, contact 999 immediately:

  • shortness of breath or difficulty in breathing
  • chest pain
  • swelling or tenderness in a leg
  • extreme weakness
  • sudden loss of vision

You can read more about the side effects of Mercilon in the patient information leaflet.

Who can take Mercilon?

Mercilon is a reliable method of contraception for all women.

There are some health conditions where taking Mercilon may make you feel worse. Do not take Mercilon if you:

  • are allergic to any of the ingredients found in Mercilon
  • are pregnant or think you might be pregnant
  • are breastfeeding
  • have ever had a blood clot
  • have a blood clotting disorder
  • have had a stroke or a heart attack or have angina (chest pain)
  • have severe diabetes with blood vessel damage
  • have very high blood pressure
  • have a high level of cholesterol (fat) in your blood
  • have migraines with aura (often visual or auditory disturbances)
  • have severe liver disease or liver tumours
  • have ever had pancreatitis (inflammation of the pancreas)
  • have cancer affected by sex hormones such as breast cancer

If you think you might be off your feet for a long time, such as after having an operation, speak to your doctor. Your risk of blood clots can increase after an operation, so your doctor may ask you to stop taking Mercilon temporarily.

Speak to your doctor before taking Mercilon if you have:

  • recently given birth
  • unexplained vaginal bleeding
  • heart disease
  • diabetes
  • kidney or liver problems
  • severe depression
  • brown patches on your skin (chloasma)
  • Crohn’s disease or ulcerative colitis
  • systemic lupus erythematosus (SLE)
  • sickle cell anaemia
  • varicose veins

For more information about whether you can take Mercilon, read the patient information leaflet. You can also speak to your doctor or pharmacist to find out if Mercilon is suitable for you.

Mercilon interactions

Other medications can interact with how Mercilon works. This means the effectiveness of Mercilon can be reduced, or that Mercilon interferes with how these medications work. Tell your doctor or pharmacist if you take any medications or over the counter products.

Some medications that interact with Mercilon are:

  • epilepsy treatment such as phenytoin, lamotrigine or carbamazepine
  • antibiotics used to treat tuberculosis like rifampicin
  • treatment for HIV or hepatitis C such as ritonavir or efavirenz
  • bosentan, a high blood pressure medication
  • St. John’s wort, a herbal remedy used to treat low mood
  • griseofulvin, an antifungal medication

If you are taking medications that make Mercilon less effective, your doctor may advise you to use condoms with the pill.

Alternative treatments

If you do not think Mercilon is right for you, there are many alternative contraceptive pills to consider. At ZAVA, we have a wide range of oral contraceptive pills that you can try.

Some combined contraceptive pills you can request from us are:

You can also try the progesterone-only pill, also known as the mini pill. The mini pill is taken continuously, which means you do not need to take a 7 day pill free break. This might be suitable for you if you have side effects related to oestrogen. Some mini pills are:

Contraceptive pills are not the only type of contraception. Hormonal contraceptives for women come in many different types, such as patches, implants, and the coil. You can read our guide on the different types of contraception, or speak to your doctor or sexual health clinic for more information.

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Medically reviewed by:
Dr Babak Ashrafi Clinical Lead for Service Expansion

Babak studied medicine at King’s College London and graduated in 2003, having also gained a bachelor’s degree in Physiology during his time there. He completed his general practice (GP) training in East London, where he worked for a number of years as a partner at a large inner-city GP practice. He completed the Royal College of GPs membership exam in 2007.

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Last reviewed: 24 Jun 2022


Contraceptive pills are a reliable way of reducing your risk of getting pregnant from sex. ZAVA offers most common brands of pill, so you can order your preferred brand by visiting our contraceptive pill service page.




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