The 5 Biggest Health Insurance Companies In The United States 2021

The 5 Biggest Health Insurance Companies In The United States 2021

The 5 Biggest Health Insurance Companies In The United States 2021, For the past six years or so, the American Medical Association’s list of the top five health insurance companies in the United States has remained relatively consistent. The list has been mostly – if not exclusively – dominated by UnitedHealth Group, Anthem, Aetna, Cigna, and Humana, taking up well over 40% of the market share.

But, there was a disruption on that list in 2020 while Covid-19 ravaged the country and the world: Kaiser displaced Humana to occupy the fifth position. It remains the same in 2021.

While there are top industry views that market share data do not necessarily reflect consumer experience or views, below are some details on the companies currently occupying the top five slots. 

UnitedHealth Group

Data from the first quarter of 2021 shows that UnitedHealth Group served nearly 50 million consumers with its various health insurance products. With this, it holds about 16% of the market share.

However, UnitedHealth seems to fare better in a nationally considered data pool. But, when the data considerations get more localized to metropolitan areas and states, its position on the market share ranking drops way down to the 3rd.

UnitedHealth has made more inroads in 2021. For instance, it went outside the norm among the Federal top health insurers by reentering the Affordable Care Act market.


With a customer base of about 44 million as of the first quarter of 2021 and a 12 percent market share, Anthem comes second on the AMA health insurers competition ranking. Its market share value has, however, depreciated by 1% over the last seven years.

Although Anthem comes second on the list under consideration, it ranks two slots above UnitedHealth Group based on more localized metropolitan and state data considerations. It is at the top of the list in this respect. While UnitedHealth has the highest market share only in 22 metropolitan statistical areas, Anthem dominates the market in a whopping 80 metropolitan areas.


With a 40 million strong consumer base, Aetna dominates 11% of the national health insurance market. Aetna’s market share value has remained the same for the past 7 years (i.e. since 2014).

Close to a quarter of Aetna’s consumer base comes from Medical Health Plan enrollment. And, while it has distanced itself from the Affordable Care Act market since 2018, Aetna announced some time ago that it would be reentering the market in 2021. The company will become the second among the top five nationally recognized insurance companies (after UnitedHealth Group).


As far as market share goes, Cigna is one of the fastest-growing among the top five health insurance companies in the United States. In the last seven years, it has seen a growth of 2%, thus, taking 10% of the market in the first quarter of 2021.

Data from the third quarter shows that the company has a little above 20 million consumers under its services. However, its performance in the Affordable Care Act market has been far from being equally good. It was never among the top 10 in this market until 2020, when it climbed into the 10th position after grabbing just 2% of the market share.


As earlier said, Kaiser is the newest member of the top 5 insurance companies in the USA according to the AMA ranking. It got to this position in 2020 from 6th the previous year. Like Cigna, Kaiser experienced a market share growth of 2% in the last 7 years, thereby occupying 7% of the national health insurance market since last year.

Kaiser occupies the fourth position by dominating 20 metropolitan statistical areas in terms of localized health insurance data considerations. It shares this position with Highmark. 


The above account represents the situation in the US national health insurance market according to the data available to us in the fourth quarter of 2021. As the year wears to an end and we look forward to 2022 and the years ahead, more disruptions on this list are expected.

This can be anticipated already from the formidable performance being put up by payers like Centene. Centene’s growth is unique for rising to the 10th position in 2020, all the way from 76th in 2014.