Blood test for gluten - however, instead of paying a doctor, you can keep a simple 2 week food diary. Cut out all carbs (good and bad) - I ate vegetable soups and salads and drank water - add a bit of GOOD carbs back in and in about 2 hours if your symptoms (mine was horrid gas, cramping, constipation) reappear, you can be pretty sure you have an INTOLERANCE to gluten (celiac disease). There is a huge difference between a food ALLERGY and a food INTOLERANCE. Allergies can be life threatening, intolerance can be uncomfortable. Both are considered celiac disease - just different degrees.
this is a great forum to find and share with Celiacs, but so many articles are already written on "how do I know that I have Celiac disease?" Maybe those would be the best start?
First, what makes you think you do? Your question doesn't really provide us with anything to go on other than a question that is easily answered on the web with articles.
You will find alot of varing opinions.
But as bistina said there is a difference between allergy and intolerance.
What is importnat is that you realize that even intolerance is life threatening if not solved by gluten free diet.
The ramifications of intolerance can still cause an onset of a mirad of other serious side effects and consequences. Including cancer.
So try a few articles, such as:
I think these will give you vast knowledge of what it is and how you know you have it.
Hope this helps.