The European Health Insurance Card (EHIC) is provided free to those E.U citizens travelling within the European Economic Area (EEA). 
 
What does the EHIC cover?

 It will cover any medical treatment that becomes necessary during your stay because of either illness or an accident. 
  
 The card gives access to reduced-cost or free medical treatment from state healthcare providers. 
  
 It allows you to be treated on the same basis as a resident of the country you are visiting i.e. you may have to pay a patient contribution (also known as a co-payment). You may be able to seek reimbursement for this when you are back in the UK if you are not able to do so in the other country. 
  
 It includes treatment of a chronic or pre-existing medical condition that becomes necessary during your visit. 
  
 It includes routine maternity care, (provided the reason for your visit is not specifically to give birth). 
  
 It includes the provision of oxygen, renal dialysis and routine medical care. 

What will the EHIC not cover?

 The EHIC is not a substitute or replacement for private travel insurance. You should always take out an appropriate private policy in addition to carrying your EHIC. 
  
 It will not cover the costs of private healthcare or services that are not part of the state healthcare system.  
  
 It will not cover the costs of being brought back to the UK (repatriation).
  
 It will not allow you to go abroad to specifically receive treatment (including going abroad to give birth). 
  
 The card may not be used in some regions, as there may be no state provided healthcare available.

Presenting the EHIC entitles you to treatment that may become necessary during your trip, but doesn't allow you to go abroad specifically to receive medical care. However, maternity care, renal dialysis and managing the symptoms of pre-existing or chronic conditions that arise while abroad are all covered by the EHIC.

Article Reference: http://www.nhs.uk/NHSEngland/Healthcareabroad/EHIC/Pages/Introduction.aspx