A UK European Health Insurance Card (EHIC) or UK Global Health Insurance Card (GHIC) does not cover going abroad for planned medical treatments.
A UK EHIC or UK GHIC is for necessary healthcare when you're travelling. Necessary healthcare means healthcare that becomes medically necessary during your stay, and you cannot reasonably wait until you're back in the UK to get it.
If you’re thinking about having medical treatment in another country, you may be entitled to NHS funding in an EU country or Switzerland.
The S2 (planned treatment) route
An S2 is issued for UK residents who are entitled to treatment on the NHS to receive planned treatment in a European Economic Area (EEA) country or Switzerland.
For more information on if you’re eligible and what funding may be available, visit the S2 funding route page on the NHS website.