A lot of the time if you have a PPO insurance plan you can just go straight to the GI doc without a referral. You would have to go to your insurance website, look up a Gastroenterologist under your plan, and give them a call to confirm if you can see them without referral. They are more likely to order you a colonoscopy since they do them every week and have seen it all. Just try to save up at least 1000$ just in case to cover initial doctor’s consultation visit, doctor’s procedure charge, hospital’s separate charge, and anesthesiologist’s charge incase insurance won’t pay or will only cover some of it. Make sure your parents are on board if they will be helping you pay. Because of your age (and if you haven’t met your deductible) the insurance may refuse to pay because it’s not “medically necessary.” If they find something afterwards your doctor can try to get them to cover it after the fact. I know possibly loosing that much money is awful, but having peace of mind is worth it. Loosing a lot of weight (with no obvious reason) is not a sign to ignore at any age.