EHIC is the European Health Insurance Card covering certain types of healthcare in certain countries.

For UK residents, details can be found on

For UK residents, an existing EHIC card will remain valid until the expiry date on the card. These will be replaced by either a UK EHIC card or a UK GHIC card.

You should always take out adequate travel insurance for existing medical conditions when you travel, regardless of whether or not you hold a EHIC or GHIC card.