Quick answer: By the number of people they cover, the biggest health insurers in the USA include UnitedHealthcare, Elevance Health (which sells Anthem plans), Aetna (part of CVS Health), Cigna, Humana, Kaiser Permanente, Molina Healthcare, Centene’s Ambetter and Oscar Health, plus the 33 independent Blue Cross Blue Shield companies. Size is not the same as “best” for you. The right insurer is the one whose plan includes your doctors and medicines, fits your total budget and is actually sold where you live.
This list keeps the ten names from the original article and updates each entry with membership figures that the companies themselves reported. An earlier version gave 2023-era member counts that are now out of date, treated Anthem and Blue Cross Blue Shield as unrelated companies, and described Ambetter as a Medicaid and Medicare insurer. Those points are corrected below.
How we chose and how to read this list
“Top” here means large and widely available, not a quality ranking. We have not tested or rated these insurers. For each one we used the latest membership figure the company published, and we state the date of every figure. Membership counts are measured differently by each company (for example, some include people in employer plans that the insurer only administers), so use them to judge scale, not to compare quality.
Major US health insurers at a glance
| Insurer | Parent company | Main markets | Members reported |
|---|---|---|---|
| UnitedHealthcare | UnitedHealth Group | Employer, individual, Medicare, Medicaid | 49.8 million medical members (end of 2025) |
| Anthem | Elevance Health | Employer, individual, Medicare, Medicaid | About 45 million medical members (end of 2025) |
| Aetna | CVS Health | Employer, Medicare, Medicaid, individual | 26.6 million medical members (end of 2025) |
| Cigna Healthcare | The Cigna Group | Mainly employer plans | About 16.4 million US medical customers (end of 2025) |
| Humana | Humana Inc. | Mainly Medicare Advantage | About 15 million medical members (end of 2025) |
| Kaiser Permanente | Kaiser Foundation Health Plan | Integrated plan and care in selected states and Washington, D.C. | 12.9 million members (30 June 2026) |
| Blue Cross Blue Shield | 33 independent companies | All 50 states, D.C. and Puerto Rico | 118 million members (BCBSA figure) |
| Molina Healthcare | Molina Healthcare Inc. | Mainly Medicaid, plus Medicare and Marketplace | About 5.5 million members in 21 states (end of 2025) |
| Ambetter | Centene Corporation | ACA Marketplace (individual) plans | About 5.5 million Marketplace members (end of 2025) |
| Oscar Health | Oscar Health Inc. | ACA individual and small-group plans | About 2.04 million members (end of 2025) |
The ten insurers in detail
UnitedHealthcare
UnitedHealthcare is the insurance arm of UnitedHealth Group and the largest single insurer on this list. In its full-year 2025 results, the company reported 49.8 million medical members. That included about 29.7 million in commercial (employer) plans, 8.4 million in Medicare Advantage and 7.4 million in Medicaid. The original article said “more than 70 million”; that figure does not match the company’s medical membership. UnitedHealth Group also said it expected membership to fall in 2026.
Anthem (Elevance Health)
Anthem plans are sold by Elevance Health, which changed its corporate name from Anthem, Inc. in 2022. In many of its states, Anthem operates as a Blue Cross Blue Shield licensee, so Anthem and “Blue Cross Blue Shield” overlap rather than being two separate insurers. Elevance’s 2025 annual report shows medical membership of about 45 million at the end of 2025, down about 1% over the year, mainly because of Medicaid eligibility checks.
Aetna (CVS Health)
Aetna has been part of CVS Health since 2018. CVS Health reported 26.6 million medical members at the end of 2025, down about half a million from a year earlier. The company said the fall came mainly from individual exchange (Marketplace) and government plans.
Cigna Healthcare
Cigna Healthcare belongs to The Cigna Group and focuses on employer-sponsored plans, many of them self-funded by the employer. In March 2025, Cigna sold its Medicare Advantage, Medicare Part D and related businesses to Health Care Service Corporation (HCSC). At the end of 2025, it reported about 16.4 million medical customers in the US and 18.1 million in total, including its international health business.
Humana
Humana is now mainly a Medicare insurer. It announced in February 2023 that it would leave the employer group commercial medical business. Humana reported about 15 million medical members at the end of 2025, including 5.2 million in individual Medicare Advantage plans. The original article described Humana as selling to individuals, families and employers; for people under 65, that is no longer its focus.
Kaiser Permanente
Kaiser Permanente is different from the other names here. It combines a not-for-profit health plan with its own hospitals, medical offices and physician groups. Its own fast facts put membership at 12.9 million as of 30 June 2026, served in its regions: Northern and Southern California, Colorado, Georgia, Hawaii, the Mid-Atlantic states (Maryland, Virginia and Washington, D.C.), Nevada, Oregon and Washington. If you do not live in one of those areas, you generally cannot buy a Kaiser plan.
Blue Cross Blue Shield
Blue Cross Blue Shield is not one company. The Blue Cross Blue Shield Association (BCBSA) licenses the brand to 33 independent, locally operated companies, each with its own territory, plans and prices. BCBSA says these companies together have 118 million members across all 50 states, Washington, D.C. and Puerto Rico. Because each Blue company is separate, quality and pricing can differ a lot from one state to the next.
Molina Healthcare
Molina focuses on government-funded coverage, mainly Medicaid, along with Medicare plans and some Marketplace plans. Its 2025 annual report says it served about 5.5 million members in 21 states at the end of 2025. Molina’s own guidance expects lower membership in 2026.
Ambetter (Centene)
Ambetter is Centene Corporation’s brand for individual health plans sold on the Affordable Care Act (ACA) Marketplace. An earlier version of this article said Ambetter serves people eligible for Medicaid and Medicare; that was wrong. Centene runs its Medicaid and Medicare plans under other names. Centene reported about 5.5 million Marketplace members at the end of 2025 and expected that number to fall in 2026.
Oscar Health
Oscar Health sells individual (ACA) and small-group plans and is known for its app-based approach to finding doctors and managing claims. The original article said Oscar covered “more than half a million” people. Oscar’s year-end 2025 membership table showed about 2.04 million members, and the company reported about 3.4 million people enrolled as of 1 February 2026, after the 2026 open enrolment period.
How to compare health insurance companies
The useful factors from the original article still apply. Here is how to check each one:
- Provider network. Search the plan’s online directory for your doctors, nearby hospitals and pharmacy before you enrol. Check whether the plan is an HMO, PPO or EPO, because that decides whether out-of-network care is covered at all.
- Total cost, not just the premium. Compare the monthly premium, deductible, copays, coinsurance and the out-of-pocket maximum. A cheap premium with a high deductible can cost more if you need regular care.
- Prescription coverage. Look up each medicine you take in the plan’s drug list (formulary) and note its tier.
- Extra benefits. Some insurers sell dental, vision or life insurance alongside health plans. These are usually separate policies with their own costs.
- Complaints and service. The National Association of Insurance Commissioners (NAIC) publishes complaint data through its Consumer Insurance Search tool, and your state insurance department can tell you how a company handles complaints locally.
- Availability. Most insurers sell individual plans only in some states or counties. Enter your ZIP code on HealthCare.gov or your state’s own marketplace to see which insurers you can actually choose.
Where you buy also matters. Most people get coverage through an employer. If you buy your own plan, use HealthCare.gov or your state’s marketplace, where you may qualify for financial help. People aged 65 and over usually compare plans on Medicare.gov, and Medicaid is applied for through your state.
If you are also reviewing other cover for your family, see our guides to major life insurance companies in the US and the largest car insurance companies in the USA. Pet owners can compare pet insurance providers in the USA.
This article is general information, not insurance, medical or financial advice. Plans, prices and networks change every year, so check the insurer’s official documents and your state’s marketplace before you enrol.
Frequently asked questions
Which is the largest health insurance company in the USA?
UnitedHealthcare is the largest single insurer by medical members, with 49.8 million at the end of 2025. Taken together, the 33 Blue Cross Blue Shield companies cover more people, about 118 million according to BCBSA, but they are independent companies rather than one insurer.
Is Anthem the same as Blue Cross Blue Shield?
Partly. Anthem plans are sold by Elevance Health, which holds Blue Cross Blue Shield licences in a number of states. In those states, Anthem is the local Blue plan. In other states, a different, independent company holds the Blue licence.
Is the biggest insurer the best choice?
Not necessarily. A large insurer may have a wide national network, but the plan you can buy in your county may use a narrow local network. Check that your doctors are in network and compare total yearly costs before you decide.
Can I buy a Kaiser Permanente plan in any state?
No. Kaiser Permanente operates only in its own regions: California, Colorado, Georgia, Hawaii, the Mid-Atlantic states, Nevada, Oregon and Washington, where it runs its own hospitals and medical offices. Outside those areas, its plans are generally not available.
Where can I check complaints against a health insurer?
Use the NAIC’s Consumer Insurance Search tool, which shows complaint information for insurers, or contact your state insurance department. Both are free.
Checked in October 2026 against company-reported results for 2025 (UnitedHealth Group, Elevance Health, CVS Health, The Cigna Group, Humana, Molina Healthcare, Centene and Oscar Health), Kaiser Permanente’s fast facts (30 June 2026) and the Blue Cross Blue Shield Association’s published membership figure.
