If you have dietary restrictions, you'll need to learn how to convey that information to the people preparing your food.
Sometimes, even saying "I'm a vegetarian" isn't enough, as vegetarianism is far from a universal concept and its standards may vary by country.
Learn how to express what you can and can't eat, and if there's any doubt, have someone write down your dietary restrictions in the local language so you won't risk getting misunderstood.