Top 5 Largest Health Insurers in the US by National Market Share


UnitedHealth Group, Anthem, Aetna, and Cigna returned to the list of the top five largest health insurers and one newcomer joined the list.

UnitedHealth Group, Anthem, Aetna, and Cigna held onto their status as the top four largest insurers, but in 2020 Kaiser rose to fifth place.

AMA was careful to point out that data on national insurer market shares do not reflect the consumer’s experience of the health insurance industry. Market-level data more accurately demonstrate the impact of industry consolidation on the average consumer, the provider organization stated.

Only the top three insurers breached ten percent of the market share, which is a testament to how few health insurers are national, according to AMA.

Three of the top ten insurers with the largest national market share are each located in a single state. They achieved the highest rankings because two of the states—California and Florida—are among the states with the largest markets and sizable populations. The third—Michigan—is not very large, but one insurer dominates nearly 70 percent of the market share there.

Despite these nuances, ranking the top five largest health insurers at the national level provides a helpful backdrop for the more localized data, AMA acknowledged.


UnitedHealth Group maintained the largest market share in the nation in 2020, although its share diminished slightly compared to 2014. In 2020, the company held 15 percent of the market share, whereas six years prior UnitedHealth Group had 16 percent of the market share.

The payer boasts nearly 49.5 million consumers across all of its health insurance products, as of the first quarter of 2021.

However, when placed in the context of data from states and metropolitan statistical areas—a more localized perspective on market share—UnitedHealth Group drops to third place in market share size, where it is tied with Florida Blue. The payers can each claim the highest market share in 22 metropolitan statistical areas.

In 2021, UnitedHealthcare re-entered the Affordable Care Act marketplace, going against the tide of other national insurers. The payer joined urban exchanges in Oklahoma, North Carolina, Maryland, the District of Columbia, and Washington setting high premiums for its marketplace plans.

On the exchanges, the national insurer fell from having the second largest market share in 2015 at 11 percent to the thirty-ninth largest share in 2020 at less than 0.5 percent, according to AMA.


Anthem remained in second place to UnitedHealth Group in the national market share rankings, dropping slightly from 13 percent market share in 2014 to 12 percent market share in 2020.

The payer serves around 44 million members who are enrolled in its medical health plans, as of the second quarter of 2021.

While it may have a lower ranking in the national market share, Anthem tops UnitedHealth Group in the state and metropolitan statistical areas data.

Anthem sets the bar with the highest metropolitan statistical area market share of any insurer. The payer holds the largest market share in 80 metropolitan statistical areas, compared to UnitedHealth Group’s 22 metropolitan statistical areas.

Medicare enrollment was not included in the AMA report, but one of Anthem’s most recent endeavors that could boost its size involves expanding its Medicare Advantage plan options.

In July 2021, the payer announced that it would be partnering with Kroger Health to offer a Medicare Advantage plan in 2022. The Medicare Advantage plan will be available in four metropolitan regions in Georgia, Kentucky, Ohio, and Virginia.


Aetna kept its 11 percent market share in 2014 and 2020.

The payer serves approximately 39 million members who receive medical, pharmaceutical, or dental coverage through Aetna’s health plans. Medical health plan enrollment contributes approximately 23.4 million of its overall membership, as of the fourth quarter of 2020.

On the exchanges at a national level, Aetna had the fifth-highest market share at six percent in 2014 and the third-highest market share at nine percent in 2015. Despite this growth, the payer fled the Affordable Care Act marketplaces in 2018 along with many other major payers.

However, at the beginning of 2021, Aetna revealed that it would be re-entering the Affordable Care Act marketplaces.


Cigna saw a slight boost in its market share from 2014 to 2020, rising from eight percent to ten percent.

As of August 2021, the payer’s enrollment totaled approximately 20.4 million members, according to a ValuePenguin and Lending Tree report.

Cigna did not break into the top ten largest health insurers on the Affordable Care Act marketplace until 2020, AMA’s data revealed. That year, it edged into tenth place by attaining two percent of the market share.

In 2021, the payer announced that it will be expanding across multiple markets.

In the individual health insurance marketplace, Cigna will enter into the marketplaces in Georgia, Mississippi, and Pennsylvania for the 2022 plan year and will add more counties in Virginia, Arizona, and Florida. The payer anticipated serving an additional 1.5 million members through these markets.

Cigna also extended its small business health plan model that it started in conjunction with Oscar Health. The Cigna + Oscar plan will be available in eight counties in California.

Cigna and Oscar Health also expanded their virtual first primary care program. The program will soon be available in Tennessee and Georgia, starting in 2022 and pending regulatory approval.


Kaiser rose from sixth place to fifth place in national-level market share ranking from 2014 to 2020 by increasing from five percent market share in 2014 to seven percent market share in 2020.

At the metropolitan statistical areas data level, Highmark and Kaiser tied for the fourth-highest market share, with the biggest market shares in 20 metropolitan statistical areas.

Kaiser performed better in 2020 in the exchanges than it did in 2014 or 2015. The payer achieved the third-highest market share in 2020 with eight percent of the exchange market share. In 2014 and 2015, Kaiser hovered at sixth place for its exchange market share.

Out of the five remaining health insurers that make up the top ten list of largest health insurers on the national level in 2020, four payers boasted two percent of the market share.

Centene’s ascension to tenth place was the most notable shift in the top ten list. The payer was a new addition largest national-level market share ranking, rising from seventy-sixth place in 2014 to tenth place in 2020 and bumping Humana out of the top ten. AMA attributed this rise to Centene’s latest acquisitions and the payer’s decision to enter the exchanges.

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