A valid European Health Insurance Card gives you the right to access state-provided healthcare during a temporary stay in another European Economic Area (EEA) country or Switzerland.
The EHIC covers treatment that is medically necessary until your planned return home. Treatment should be provided on the same basis as it would to a resident of that country, either at a reduced cost or, in many cases, for free. For example, in some countries, patients are expected to directly contribute a percentage towards the cost of their state-provided treatment. This is known as a patient co-payment. If you receive treatment under this type of healthcare system, you are expected to pay the same co-payment charge as a patient from that country.
The EHIC also covers the treatment of pre-existing medical conditions and routine maternity care, provided the reason for your visit is not specifically to give birth or seek treatment. For more information about what is covered in each country, see the country-by-country guide.
The EHIC is not an alternative to travel insurance. It will not cover any private medical healthcare or costs, such as mountain rescue in ski resorts, being flown back to the UK, or lost or stolen property. It is also not valid on cruises.
It is therefore important to have both an EHIC and a valid private travel insurance policy in place before you travel. Some insurers now insist you hold an EHIC, and many will waive the excess if you have one.
courtesy of NHS.UK