If you experience an unexpected or harmful reaction to an immunoglobulin (IG) therapy product or any other medicine used to treat your immunodeficiency, it is important to report it. 

Reporting suspected adverse reactions helps improve the safety of medicines for everyone. Every report adds to the information available to healthcare professionals and regulators, helping to identify potential safety concerns and ensure medicines continue to be used as safely as possible. 

What is an adverse reaction? 

An adverse reaction (also called an adverse drug reaction or side effect) is an unintended and harmful response to a medicine. 

Adverse reactions can: 

  • occur soon after taking a medicine 
  • develop during treatment 
  • appear days or even weeks after treatment has stopped 

Not every symptom will be caused by your medicine, but it is important to report anything you think may be related. 

What should you do? 

If you think you have experienced an adverse reaction: 

  1. Tell a healthcare professional. If the adverse event is due to a medicine used to treat your immune condition, contact your specialist healthcare team or GP as soon as possible so they can advise you and, if necessary, review your treatment. 
  2. Report it through the MHRA Yellow Card Scheme. The Medicines and Healthcare products Regulatory Agency (MHRA) operates the Yellow Card Scheme, the UK's official system for collecting and monitoring information on suspected side effects and safety concerns relating to medicines and medical devices. 

You can submit a report online through the Yellow Card Scheme. 

You can also contact the medicine manufacturer. The company that makes your medicine may also collect reports of suspected adverse reactions. Contact details can usually be found on the medicine packaging, in the patient information leaflet or on the manufacturer's website. 

Why reporting matters 

Even if you are unsure whether your medicine caused the reaction, reporting it can still help. 

Yellow Card reports: 

  • help identify new or rare side effects 
  • improve understanding of known side effects 
  • contribute to ongoing monitoring of medicine safety 
  • help protect other patients by informing future safety advice and guidance 

Every report makes a valuable contribution to ensuring medicines continue to have a positive impact on people's lives while maintaining the highest possible standards of safety. 

If you have any concerns about your medication or experience symptoms that require urgent medical attention, seek advice from your healthcare team immediately or contact emergency services if appropriate. 

Find out more about the Yellow Card scheme at About the Yellow Card scheme | Making medicines and medical devices safer, including: 

Posted July 2026