UK travellers could head to Europe this summer without full cover as six million European Health Insurance cards (EHICs) are due to expire in the first half of 2011 alone.

The EHIC gives health cover in state-run hospitals and at GPs in all EU countries, plus Switzerland, Iceland, Norway and Liechtenstein. Yet many who think they're covered, aren't.

With an EHIC you pay what a local pays. If it's free for them, as in Spain, it's free for you. If they pay, as in Germany, you pay the same. See the country by country list.

The Department of Health says six million of the 23 million EHICs in circulation, which are valid for up to five years, have expired or are due to expire between January and June this year. That's in addition to the many already invalid.

Here are our tips to making the most of the EHIC:

  • Urgently check the date. If you're going to Europe ensure all cards are valid.

  • Always carry your EHIC. You must present it to be covered, so don't leave it at the hotel. Keep it in your purse or wallet.

  • Kids need their own. Include under-16s as dependents on a parent's or guardian's application form so they will get an EHIC too.

How to apply/renew

You can renew your card up to six months before its expiry date, or at any time after. The expiry date is printed on the front of your card.

Only use the official EHIC website to apply or renew and beware Googling the term EHIC as many firms that rank highly on search engines charge you for what is a free service.

The Office of Fair Trading shut down a host of websites last year that "tricked" consumers into parting with cash to get the card.

It's not a travel insurance substitute

Every traveller going to Europe should have an EHIC alongside – not instead of – travel insurance.

Full insurance often covers cancellations, repatriation, baggage loss, theft or private hospital cover which an EHIC won't.

That said, if you've got travel insurance it doesn't mean you shouldn't have an EHIC as with the latter you should get emergency cover with no questions asked, whereas a travel insurer may decline a claim.