Lisa, I had someone contact me via Feedback about two years ago asking the same thing, so I've already looked into it. You need to take a look at this website. As you'll see, there are dialysis centres that accept the EHIC card in Las Americas and Puerto de La Cruz and another private one in Puerto Santiago. The website doesn't give the actual locations of these centres, so you'll probably have to contact them for more details. There's a phone number and email address on the site.
