Gfilui

I bought a plane ticket from Turkish Airlines, 2 months before the flight. Then I went to the doctor, and the doctor said I have a health problem, which specifically forbids me to take flights for one month.

I have a valid doctor's note too. I can document this in any valid type. Does it makes me eligible for a full refund?

The conditions of carriage for your ticket do not include a provision for a refund in this case. Though there is a provision (3.2.1.3) to extend the validity of your tickets if you can't travel due to illness, but it only applies if you get sick once your trip starts.

However, many airlines will make accommodations in such situations as a customer service gesture. You can contact the airline, explain the situation, tell them you have a doctor's note, and politely ask if they can grant a refund. If they aren't able to do so, you might ask for a supervisor to see if they can make an exception. If their policy forbids a refund (airlines are generally quite reluctant to ever refund non-refundable tickets), they may be able to provide a lesser remedy, such as allowing you to reschedule the flight without paying a change fee.

If that fails, you could contact a travel advocacy journalist like Christopher Elliott to see if they can get anywhere with the airline. His site also has contact information for Turkish Airlines management (see advice on writing for help), who would be the final word on what the airline will do in this situation.

If you have travel insurance, this may be a reason for a claim as well.

As the accepted answer says, your airline doesn't have a policy to provide refunds in that case, but you may be able to get one with a personal approach.

In the event you don't succeed, you can still get a refund on airport fees and taxes. In low cost tickets (which nonrefundable ones generally are), these can amount to half the cost.

Don't settle for this, though, only as a last resort. A medical condition is a very strong reason for a full refund.

Speaking from experience, although only one particular case. My father-in-law was planning to visit us in UK from Georgia, flying with Turkish Airline. About a week before the planned trip, he was admitted to hospital in relation to a previously undiagnosed heart problem - and he was actually still in hospital on the day of the planned travel.

The ticket was a non-refundable, non-exchangeable, etc, etc. (i.e. the cheapest possible). With a note from the hospital, the airline agreed to refund the actual price of the ticket, but not the taxes and airport fees, as they don't control those. In our case, it was about half the ticket price. The remainder of the costs (i.e. taxes, fees, etc.) were covered by his travel insurance (minus USD $25 deductible).

All in all, we lost about $25 out of about $400 cost of the ticket - better than losing everything.

In this situation it will be especially important to have a note written from the doctor.
Typically there is a processing or cancellation fee so don’t expect a full refund. You might be better able to pursuade them to give you a credit that you would have to use within the year.
When you call the airline, the first person you will speak to usually doesn’t have the authority to do anything beyond the standard policy. If you are hoping to make the cancellation and get a refund or a credit, you will likely have to escalate to a manager. I encourage you to be kind as you will likely get a better result.