We do not know what type of medical insurance policy you have, but it sounds like a PPO plan. Most PPO plans will allow you to go to any doctor that you want to. This part is true, but the amount you are responsible for paying may vary based on which doctors you choose. It sounds like your insurance company paid part of the visit to the allergist, but the amount you paid was based on the out-of-network benefits described under your health plan. If you can find your original policy, this should be clearly eplained in the section that addresses accessing health care. For eample, a standard PPO plan might say that visits to a specialist are 20% in-network and 50% out-of-network. In-network refers to any physician or hospital that has a contractual agreement with your insurance company to provide services at a pre-negotiated rate. Your insurance company probably provided you with a directory of these physicians, or informed you of the location of their online provider search. If you go to a doctor that is not in this directory, they are considered out-of-network and you coinsurance will be higher. In addition to that, these non-network doctors do not have pricing agreements with your insurance company, so the amount they charge you will often be higher. Your insurance company may also make you responsible for an ecess charges if the rates charged to you by the allergist are deemed unreasonable.