Mercilon is a combined oral contraceptive pill used to prevent pregnancy. Mercilon is a 21-day Pill – you take one each day for 21 days, followed by 7 days when you take no pills.

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What is Mercilon?

Mercilon is a combined oral contraceptive pill (‘the Pill’) taken to prevent pregnancy.

This low-dose contraceptive contains two types of female sex hormones, oestrogen and progestogen. These hormones prevent an egg from being released from your ovaries so you can’t get pregnant. Mercilon also makes the fluid (mucus) in your cervix thicker which makes it more difficult for sperm to enter the womb.

The benefits of taking the Pill include:

  1. it is one of the most reliable reversible methods of contraception if used correctly
  2. it doesn’t interrupt sex
  3. it usually makes your periods regular, lighter and less painful
  4. it may help with pre-menstrual symptoms.

Mercilon will not protect you against sexually transmitted infections, such as Chlamydia or HIV. Only condoms can help to do this.

How to take Mercilon

Take Mercilon every day for 21 days.

Mercilon comes in strips of 21 pills, each marked with a day of the week.

  • Take your pill at the same time every day.
  • Start by taking a pill marked with the correct day of the week.
  • Follow the direction of the arrows on the strip. Take one pill each day, until you have finished all 21 pills.
  • Swallow each pill whole, with water if necessary. Do not chew the pill.

Then have seven pill-free days.

After you have taken all 21 pills in the strip, you have seven days when you take no pills. So, if you take the last pill of one pack on a Friday, you will take the first pill of your next pack on the Saturday of the following week.

Within a few days of taking the last pill from the strip, you should have a withdrawal bleed like a period. This bleed may not have finished when it is time to start your next strip of pills.

You don’t need to use extra contraception during these seven pill-free days – as long as you have taken your pills correctly and start the next strip of pills on time.

Then start your next strip

What if I miss a dose?

A missed pill

If you miss a pill, follow these instructions:

Less than 12 hours ago

  • Take the delayed pill straight away, and further pills as usual. This may mean taking two pills in one day.
  • Don’t worry your contraceptive protection should not be reduced.

More than 12 hours ago, or you have missed more than one pill

  • Take the most recently missed pill straight away.
  • Leave any earlier missed pills in the strip.
  • Take your further pills as usual. This may mean taking two pills in one day.
  • Use extra precautions (condoms for instance) for the next 7 days.
  • Check how many pills are left in the strip after the most recently missed pill.

(Please read the patient leaflet included with your pack of Mercilon for more information on missed pills.)

A lost pill

If you lose a pill,

Either take the last pill of the strip in place of the lost pill. Then take all the other pills on their proper days. Your cycle will be one day shorter than normal, but your contraceptive protection won’t be affected. After your seven pill-free days you will have a new starting day, one day earlier than before.

Or if you do not want to change the starting day of your cycle, take a pill from a spare strip. Then take all the other pills from your current strip as usual.

You can then keep the opened spare strip in case you lose any more pills.

If you are sick or have diarrhoea

If you are sick (vomit) or have very bad diarrhoea your body may not get its usual dose of hormones from that pill.

If you vomit within 3 to 4 hours after taking your pill, this is like missing a pill. You must follow the advice for missed pills

If you have severe diarrhoea for more than 12 hours after taking Mercilon follow the instructions if you are more than 12 hours late.

Side effects & precautions

When should you not use Mercilon?

You should not use Mercilon if you have any of the conditions listed below.

Your doctor will discuss with you what other form of birth control would be more appropriate.

  • If you have (or have ever had) a blood clot in a blood vessel of your legs (deep vein thrombosis, DVT), your lungs (pulmonary embolus, PE) or other organs
  • If you know you have a disorder affecting your blood clotting
  • If you need an operation or if you are off your feet for a long time
  • If you have ever had a heart attack or stroke
  • If you have regular migraines
  • If you have or have recently had a severe liver disease
  • If you have or have had a pancreatitis
  • Known or suspected pregnancy
  • if you have cancer affected by sex hormones – such as some cancers of the breast, womb lining or ovary
  • if you have vaginal bleeding that has not been explained by your doctor
  • if you are allergic (hypersensitive) to any of the ingredients in Mercilon
  • if you have hepatitis C and are taking medicinal products containing ombitasvir/ paritaprevir/ ritonavir and dasabuvir

If you suffer from any of these or get them for the first time while taking Mercilon, contact your doctor as soon as possible. Do not take Mercilon.

Blood Clots

Using a combined hormonal contraceptive such as Mercilon increases your risk of developing a blood clot compared with not using one.

It is important to remember that the overall risk of a harmful blood clot due to Mercilon is small.

Factors that increase your risk of a blood clot in a vein

The risk of a blood clot with Mercilon is small but some conditions will increase the risk. Your risk is higher:

  • if you are very overweight (body mass index or BMI over 30kg/m2)
  • if one of your immediate family has had a blood clot in the leg, lung or another organ at a young age (e.g. below the age of about 50). In this case, you could have a hereditary blood clotting disorder
  • if you need to have an operation, or if you are off your feet for a long time because of an injury or illness, or you have your leg in a cast. The use of Mercilon may need to be stopped several weeks before surgery or while you are less mobile. If you need to stop Mercilon ask your doctor when you can start using it again
  • as you get older (particularly above about 35 years)
  • if you gave birth less than a few weeks ago.

The risk of developing a blood clot increases the more conditions you have.

Air travel (> 4 hours) may temporarily increase your risk of a blood clot, particularly if you have some of the other factors listed.

It is important to tell your doctor if any of these conditions apply to you, even if you are unsure. Your doctor may decide that Mercilon needs to be stopped.

If any of the above conditions change while you are using Mercilon, for example, a close family member experiences a thrombosis for no known reason; or you gain a lot of weight, tell your doctor.

Possible interactions

Some medicines may stop Mercilon from working properly. These include medicines used for the treatment of:

  • epilepsy(primidone, phenytoins, phenobarbital, carbamazepine, oxcarbazepine, topiramate, felbamate, modafinil)
  • tuberculosis(rifampicin)
  • HIV infections(ritonavir, nelfinavir, nevirapine, efavirenz)
  • Hepatitis C virus infection (e.g., boceprevir, telaprevir)
  • Some infectious diseases (e.g., griseofulvin)
  • depressive moods(the herbal remedy St. John’s wort)

Your doctor will prescribe another type of contraceptive prior to the start of the treatment with these medicinal products.

Mercilon can be restarted approximately 2 weeks after completion of this treatment.

Side effects

Like all medicines, Mercilon can cause side effects, although not everybody gets them. If you get any side effects, particularly if severe and persistent, or have any change to your health that you think may be due to Mercilon, please talk to your doctor.

Common Side effects:

  • Headache
  • Putting on weight
  • Breast problems, such as painful or tender breasts
  • Depression or mood changes
  • Stomach problems, such as nausea; abdominal pain

Uncommon side effects:

  • Migraine (see a doctor as soon as possible if this is your first migraine or it’s worse than usual, or if the headache is severe, unusual or long-lasting)
  • Fluid retention (swollen hands, ankles or feet – a sign of fluid retention)
  • Decreased sexual desire
  • Vomiting
  • Diarrhoea
  • Skin problems, such as rash or hives
  • Breast enlargement

Tell your doctor, pharmacist or family planning nurse if you are worried about any side effects which you think may be due to Mercilon. Also, tell them if any existing conditions get worse while you are taking Mercilon.

Reporting of side effects

If you get any side effects, talk to your doctor, family planning nurse or pharmacist. This includes any possible side effects not listed in this leaflet.

You can also report side effects directly via the Yellow Card Scheme at: or search for MHRA Yellow Card in the Google Play or Apple App Store. By reporting side effects, you can help provide more information on the safety of this medicine.

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