Can a endoscopy show if you're lactose intolerance ?

Likely not: Your gut membrane does not change when you have lactose intolerance so it's unlikely that endoscopy can make a diagnosis. In lactose intolerance person, taking lactose is like taking a laxative. The difference is latose is a natural sugar and can be digested by your gut bacteria. That's how bloating and flatulence occur when affected person drinks milk.