The short answer to this question is no. EHICs will not be affected by Brexit – at least not for the time being.
The long answer gets a little more complicated. On 23rd June 2016, the UK voted to leave the European Union, and on 30th March 2017, the Prime Minister triggered Article 50. This began the legal procedure of the UK separating from the EU – a process now commonly known as ‘Brexit’.
However, there is first a two year negotiating period. Until the UK leaves the EU it remains a full member, and its citizens enjoy all the rights they did before Article 50 was triggered.
The process of leaving the EU is anticipated to be complete on 29th March 2019. But it may take longer than this if any negotiation to extend this period is successful – or shorter if negotiations wrap up early. However, this seems unlikely.
What we can say for sure right now, is that while the UK is still a member of the EU, EHICs will remain valid, and can still be renewed. So until the 29th March 2019, there will be no impact or change to the way your EHIC works.
After that date, things become a little less clear. EHICs are not only valid within the EU, but also within the European Economic Area (EEA) and Switzerland. The EEA consists of all countries in the EU, plus Iceland, Liechtenstein and Norway. Depending on the outcome of the UK’s negotiations with the EU, it may remain a member of the EEA. Or there is the possibility that it will still be a member of the single market after Brexit, but not a part of the EEA – like Switzerland.
It’s unlikely that we’ll know exactly how EHICs will be affected by Brexit until nearer the negotiating deadline. But for the moment, there is no reason to worry. You can continue to use any valid EHIC as normal for the time being. Don’t forget to take it with you when you go on holiday, and be sure to renew as soon as possible if it expires.