Here is my annual health and insurance regimen, preparatory to traveling on Camino. By spreading out things to be taken care of and making them part of my regular routine, everything gets done well in advance, without too much strain on my finances.
Bascially, I use two, overlapping methods of insurance.
First, I have travel insurance through my credit card. But as others have said, check the fine print.
Second, I always buy the optional trip insurance from the airline I use to fly to and from Spain. The cost is incidental and covers me as long as I am in Spain. Coverage is for "normal" activities usually undertaken by travelers.
High risk activities are not covered. So, walking (hiking) the Camino is considered normal. However, mountaineering is not an included activity. So, stay away on the Camino paths...
This is in part redundant, but is sufficient to get me returned home in the event of a major illness.
My primary health insurance cover in the US, Blue Cross - Blue Shield, also provides international cover through Allianz, IIRC. I can use the University at Santiago Hospital. Along the various routes, there is an online locator for hospitals and doctors by specialty. In five Caminos, I have not used it. But it is reassuring to know it is there, as a backstop.
One other way to avoid needing medical insurance while you are away on Camino is to treat your body like a car, preparing it for a long distance trip. My usual Camino season is April - May.
So, starting in December, I have my annual physical examination and lab work. While there, I obtain prescriptions for fresh antibiotics for puncture wounds, bronchial infections and middle ear infections. This usually includes Amoxicillin, Azithromycin and Ciprofloxacin. I fill the prescriptions in late March or early April, before I travel.
In January, I have my eye exam. This timing permits time to obtain new eyeglasses if my prescription changes.
In February and March I have a regular semi-annual dentist visit for cleaning and exam, as well as medical specialist examinations and lab work as needed.
By 1 April, I am medically certified as healthy, and with no evident medical issues. I would have these exams and labs done anyway. So, I just arranged them to provide up-front support to my Camino activity.
I hope this helps the dialog.