FAQs

  • Who monitors the safety of medicines in the United Kingdom?

    The Medicines and Healthcare products Regulatory Agency (MHRA) is the government agency responsible for ensuring that medicines and medical devices work, and are acceptably safe.  We keep watch over medicines and devices, and take necessary action to protect the public promptly if there is a problem.

    Please note that we are not able to provide individual medical advice to patients if you are worried about a suspected side effect, you should seek medical advice from a doctor or pharmacist.  You can also get information from

    • NHS Direct in England and Wales on 0845 46 47 or
    • NHS24 in Scotland on 08454 24 24 24.
  • Why do medicines have side effects?

    Any medicine may produce unwanted side effects (also known as adverse drug reactions).

    Many side effects are linked to the way the medicine works to treat a patient.  For instance, medicines known as 'beta-blockers' treat high blood pressure by acting on particular sites in the muscles of blood vessels, causing the muscles to relax, and reducing blood pressure.  This medicine however also acts on the same type of sites in the heart, which may cause an undesirable effect in some patients where the heart beat is slowed down.  


    Some side effects, however, are not clearly linked to how the medicine works in the body and so are more unpredictable.  As individuals, different patients may respond in different ways to the same medicine and so it is very difficult to predict whether a patient will experience any side effects.

  • Why might a medicine become available before all its side effects have been identified?

    Before a medicine is licensed, it will be tested in a series of clinical trials.  Such trials are carried out in a relatively small number of patients - on average 1,500 for a new medicine.  In addition, clinical trials are conducted under very strict conditions.  In everyday life, medicines will not be used under trial conditions and may be used by millions of patients across a range of age groups, who may also be taking other medicines and who have varied lifestyles.


    Although clinical trials are generally able to identify the more common and predictable side effects of medicines, rarer side effects may only be highlighted once the medicine is used by a far greater number of patients under the conditions of every day use.  In addition, some side effects may not be discovered until many people have used the medicine over a period of time.  Side effects can also occasionally appear after stopping a medicine.

  • If all medicines have side effects does this mean no medicine is safe?

    No effective medicine is entirely free of side effects; however, most side effects are not very common.  In general, the majority of people who take a particular medicine do not experience any serious side effects.  Even side effects that are described as common may only occur in a few people in every 100 who take the medicine. 

    When you decide with your doctor that you should take a medicine, you should consider both the risk that you may possibly experience a side effect and the benefit that you will gain from the medicine.  For instance, if you are taking a medicine to treat cancer, you might be more willing to accept the possibility of side effects than if you are simply treating a mild or short term complaint.

    When determining whether a medicine should be granted a licence for use in the United Kingdom, an analysis of the risk-benefit balance of the medicine is undertaken.  With information from trials, the potential benefits of the medicine in curing or relieving the symptoms of the condition for which it is intended to be used are considered alongside:

    • the potential risks of the side effects the medicine might cause, and
    • the risk to the patient if the condition is not treated.


    The medicine will only be given a licence if the benefits of its use in patients are shown to justify or outweigh these risks

  • How are medicines monitored in order to ensure that new side effects are detected?

    The main way in which the MHRA monitors medicines safety is to collect reports of possible or suspected side effects from patients and health professionals. These reports are made on 'Yellow Cards'. Pharmaceutical companies also have a legal obligation to pass on reports that they receive about suspected side effects of their products that are defined as serious.  These reports are made on 'Yellow Card' reporting forms.

    We enter Yellow Card reports onto a specialised database that allows rapid processing and analysis of the reports.  Since the Yellow Card Scheme was set up in 1964, over 600,000 UK Yellow Cards have been received.

    Yellow Card reports are evaluated each week to find possible previously unidentified hazards and other new information on the side effects of medicines.  We also evaluate information on medicines safety from other data sources from the United Kingdom and from around the world, including the MHRA General Practice Research Database (more information is available at www.gprd.com) and from information collected by other medicines regulators around the world.

    When we identify a new possible side effect or learn more about a recognised one, we carefully consider this in the context of the overall side effect profile for the medicine.  We also consider this information in comparison with the side effects of other medicines that can be used to treat the same condition, and re-evaluate the risk-benefit balance of the medicine.  If necessary, we will take action to ensure that the medicine is used in a way that minimises risk, and maximises benefits to the patient.  Action might include requiring details of a new side effect to be included in the product information for a medicine, a reduction in recommended dosage might be required, or we may give out warnings about groups of patients who should not be prescribed the medicine.  Sometimes, we may need to withdraw a medicine from the market altogether, when we believe that the risks of a medicine are greater than its potential benefits.

  • Since starting my medicine, I have noticed a number of new symptoms that I think may be due to the medicine. What should I do?

    If you are worried about a suspected side effect, you should seek medical advice from a doctor or pharmacist.  You can also get information from

      • NHS 111 in England and Scotland on 111 or
      • NHS Direct in Wales on 0845 46 47.


    If you think a medicine, vaccine or herbal or complementary remedy has caused an unwanted side effect, please report the problem on a Yellow Card. You can report a suspected side effect in the following ways:

    • On this website
    • On a Yellow Card form, which you can find at pharmacies, GP surgeries or from the Yellow Card hotline by calling freephone 0808 100 3352 during business hours. The Yellow Card form can also be downloaded, to print and complete (the form should be returned to the address on the bottom of the form no stamp is needed).   Download Patient Yellow Card form to print and complete
    • To the Yellow Card hotline on freephone 0808 100 3352 during business hours.

    When deciding if your new medicine may have caused the symptoms you are experiencing, a number of factors should be taken into account. If symptoms begin after you start a new medicine, they may be related to this medicine, but this will not always be the case. Your symptoms may be related to a medical condition that you have, or may simply be coincidental, particularly if you experience symptoms that commonly occur within the population, for instance headache. It is also possible that symptoms may be the result of an interaction between a new medicine, and a medicine or remedy already being used. If your symptoms stop after the medicine is stopped, this may suggest that they are more likely to have been caused by the medicine.

    Your doctor or health professional is in the best position to advise what might have caused your symptoms, and will be aware of your individual medical history, any other medicines you are taking, and any other relevant information. Your doctor will be able to give you advice about any symptoms you are experiencing, whether or not they are associated with the medicine you are taking.
    We encourage patients and health professionals to complete a Yellow Card report on any suspected side effects from taking a medicine.

  • What will happen to a Yellow Card report that I complete?

    We collect the Yellow Cards and enter them onto a specialised database that allows us to process and analyse the reports rapidly.  We evaluate the reports on a weekly basis in order to identify previously unidentified potential hazards, and new information on recognised side effects.  Your Yellow Card report will be considered in the context of all other reports received from patients or health professionals for that medicine.  We also evaluate information from additional sources such as the world-wide medical literature, and data from a number of world-wide databases.  The MHRA may use your Yellow Card report in a range of different ways, including:

    • Highlighting the report as a possible safety issue on the MHRA database and keeping a close watch on the safety of the medicine by monitoring similar reports
    • Conducting a specific analysis of similar Yellow Card reports to identify potential safety signals
    • Noting the patient perspective of a suspected side effect, to better understand the impact of side effects on the people who use medicines
    • Requesting additional information from you so MHRA scientists can better understand the suspected side effect
    • Requesting further information from other sources, including from the manufacturer/s of the medicine
    • Discussing the suspected side effect with other medicines regulatory agencies, within and outside the European Union.


    When we identify a new possible side effect or learn more about a recognised one, we carefully consider this in the context of the overall side effect profile for the medicine.  We also consider this in comparison with the side effects of other medicines which can be used to treat the same condition, and compare the risks with the benefits of the medicine as described above. If necessary, we may take action to ensure that the medicine is used in a way which minimises risk, and maximises benefits to the patient.  We might include details of a new side effect in the product information, reduce the dose to be used, or give out warnings about groups of patients who should not be given the medicine.  In rare circumstances, we may need to withdraw a medicine from the market, when we believe that the risks of a medicine are greater than its potential benefits.

  • If I complete a patient Yellow Card directly, will my doctor or health professional get a copy?

    On the patient Yellow Card form, you can indicate if you would like to the MHRA to send a copy of the report you have made to your GP or another health professional.  A copy of the Yellow Card report that you submit will not passed on to anyone without your agreement.

  • Do Yellow Card reports contain personal details about me?

    For Yellow Card reports completed by patients or members of the public:
    Completed Yellow Cards include  personal contact information.  We ask for these details so that we can get in touch if more information on the Yellow Card report is needed.  The information you provide will be kept safe, secure and confidential.  Personal data will not be passed to any person outside the MHRA without your express permission.  Furthermore patient and reporter details are excluded from the information that we are legally obliged to provide through the Freedom of Information act.  You can also ask someone else to send a report in about a suspected side effect if you do not wish to give us your name.   

    For Yellow Card reports completed by a health professional:
    Yellow Card reports that health professionals use to report suspected adverse reactions do not include personal information about patients which could be used to identify an individual (such as name or address).

    The MHRA does, however, need to know the age and gender of the person who experienced the suspected ADR as this information is important in investigating the factors which may make certain patients more likely to experience a particular side effect.

    It is most helpful if the health professional creates a patient identification code on the Yellow Card so they know who the report is about.  The MHRA is not able recognise the identifier as and is therefore unable to identify the person on the Yellow Card.  The health professional can use the code to identify the patient if the MHRA needs to ask for more information about a patients suspected side effect experience.

  • Can you tell me if a report is made by a health professional about me without my knowledge?

    Patient names or dates of birth are not included on Yellow Card reports completed by health professionals; the MHRA is not able to tell whether a report relating to an individual has been sent to us by a health professional.  If you have told your healthcare professional about a suspected side effect you have experienced with your medicine, and unsure whether it has already been reported to us, we advise that you either speak to him/her directly.  Alternatively you may wish to complete a Yellow Card yourself; we have systems in place that can detect duplicate Yellow Cards submitted from different reporters.