UnitedHealthcare, part of UnitedHealth Group, is the largest health insurance company, based on revenue. UnitedHealthcare sells individual and family plans as well as group plans, which you get through an employer.

UnitedHealthcare also has a network of over 1.3 million doctors and health care professionals, with more than 6,500 hospitals. This means that if you have UnitedHealthcare, you will have many options for where you can get medical care.

You can buy policies individual and family plans from UnitedHealthcare in 30 states. UnitedHealthcare is headquartered in Minnetonka, MN.

Kaiser Permanente is the second-largest provider of health insurance in the U.S. by revenue but the largest by enrollment for group and individual health insurance. Much of its membership comes from group health insurance plans from employers. The company also sells low-cost plans across a variety of coverage types including individual health insurance, Medicare Advantage and Medicaid.

Kaiser Permanente only sells policies in eight states and Washington, D.C., but it's very popular where it's available. The insurance company's focus is on low-cost HMO plans that require you to use one of Kaiser's medical centers to get health care, unless it's an emergency.

Anthem, which is part of Elevance Health, is the third-largest medical insurance provider by revenue and has over 6.3 million health insurance members. The company offers insurance to large and small businesses, individuals and families.

The company currently only sells plans in 14 states.

Anthem is part of the Blue Cross Blue Shield Association, which, in total, covers all 50 states. This can give you some benefits like nationwide access to medical care through the BlueCard program, which lets you use your coverage easily when you're traveling. The Blue Cross Blue Shield provider network is the largest in the country and includes about 90% of doctors and hospitals.

Centene is a large health insurance company, and most of its health insurance plans come from Ambetter. As a company, Centene is the fourth-largest major medical insurance company in the United States by revenue. It sells the most individual health insurance plans of any company, with 4,480,374 members in 2024.

Ambetter is one of Centene's main individual health insurance companies. But Ambetter doesn't sell Medicare Advantage or Medicare Part D plans. Instead, Wellcare is the main Centene subsidiary selling these policies.

Centene was started in 1984 as a provider of Medicaid plans, and today, it's the largest provider of managed care Medicaid plans — where a health insurance company oversees Medicaid benefits — in the country.

HCSC, which stands for Health Care Service Corporation, is the fifth-largest health insurance company by revenue and enrollment, with over 5.6 million customers. The company's name may not be familiar to most people, but HCSC operates Blue Cross Blue Shield companies in Illinois, Montana, Nevada, Oklahoma, and Texas.

In addition to managing health insurance companies, HCSC also works with local nonprofits to strengthen the communities it serves. HCSC provides funding to nonprofits that help improve nutrition, economic development, housing and more.

HCSC was founded in 1936. Today, the company also owns brands such as Collective Health, the Dearborn Group and Prime Therapeutics.