Or ask your pharmacist, who presumably also knows all of your medications.
I have been on warfarin for nine years, and I personally have not heard of this with warfarin. There are other heart and blood pressure-type drugs that occasionally do have this side effect, though. If it has happened to you, you might consider whether another one of your medications could possibly to be the cause. If you will do an internet search for a list of photosensitive medications, you will find a number of drugs that can cause photosensitivity as a side effect. I don't believe it's ever really common, but yes, there are some drugs are known to do this in susceptible people. It can also be called sun sensitivity, sun allergy, or photoallergy. Of course, it goes without saying that you could ask your doctor about it. You could also write in to the Expert Forum on this site and list all of your medications to see if any of them are known for photosensitivity.