You could pay higher costs. Review your Summary of Benefits to find out when you need a referral from your primary care physician for the costs to be covered.
In an Health Maintenance Organization (HMO) plan, one physician or nurse practitioner is designated to serve as your primary care doctor, and that person provides most of your medical care, including referring you to specialists and other health care professionals as needed. If you see a specialist without getting a referral from your primary care doctor, your insurance company will not cover the care and you are responsible for all health care costs. Referrals have expiration dates, and some even have a limited number of visits that are allowed. So, if you need to see the specialist after the expiration date or the allowed visits, you need another referral from your primary care doctor. If you do not get the referral, you will incur higher costs.
A Preferred Provider Organization (PPO) plan offers a limited set of in-network providers, and when you use them, a greater share of your medical bills will be covered. You do not need a referral to see a specialist or other health care provider. Unlike an HMO plan, if you use an out-of-network provider, you will still receive some insurance coverage, but your costs will be greater than if you choose an in-network provider.