Largest Health Insurance Companies in the US, Ranked by Market Share
The biggest US health insurers ranked by NAIC-reported accident-and-health market share and direct written premium -- the actual size of each carrier's book of business, not a marketing claim.
Research period:
What this ranks: NAIC-reported accident-and-health market share, the size of each carrier's written premium, not price, service quality, complaint record, or which insurer is right for you. See PlainInsurer's complaint and denial-rate rankings for those dimensions, and compare quotes and plan details directly before you buy.
Research question
Among the 125 largest US health insurers by NAIC-reported accident-and-health market share, what share of total direct written premium is concentrated in the top 10, and what is the absolute gap between the largest and the tenth-largest insurer?
Methodology
This ranking reflects the 10 largest health insurers by accident-and-health market share, drawn from the NAIC 2024 Market Share Reports For the Top 125 Accident and Health Insurance Groups and Companies. Records are ranked by direct written premium (rank, highest first) and the top 10 of 125 rated companies are shown. Every figure updates automatically as new NAIC filings are processed; nothing on this page is hand-entered.
Coverage and exclusions: NAIC occasionally suppresses values for confidentiality, small sample size, or quality control, and suppressed rows are excluded from this ranking rather than shown as zero. If NAIC later revises a figure, the revised value replaces the old one automatically the next time the portal's data is refreshed.
Data provenance: NAIC publishes the Market Share Report on its own release schedule -- the 2024 report (covering calendar-year-2024 premiums) was published in 2025. We pull each release as it becomes available and normalize it into our database via a documented, re-runnable extraction script; a later release simply supersedes the one before it, so readers never see a mix of old and new figures on the same page.
Comparability across years: when NAIC revises its release schedule, definitions, or coverage, we note the affected years on the methodology page so readers can compare like-with-like rather than across a changed measurement.
Editorial governance: PlainInsurer publishes its editorial policy and corrections process. If an insurer disputes a figure attributed to it, the correction is checked against the official NAIC record before any change is made.
Every number on this page can be traced back to its NAIC source by following the citation below, so independent verification never requires anything beyond the original public source. See the methodology page for the complete ETL pipeline, source vintage, and column lineage.
Largest health insurers by accident-and-health market share
Live data: reflects the current NAIC 2024 Market Share Report snapshot
The ranked top 10
Every row below reflects the current 10-company dataset out of 125 rated health insurers. Reload the page after new NAIC data is processed to see the latest values.
| # | Rank | Health insurer | Market share % | Direct written premium |
|---|---|---|---|---|
| 1 | 1 | UnitedHealth Group | 16.1% | $269.45B |
| 2 | 2 | CVS Group | 7.2% | $121.24B |
| 3 | 3 | Centene Corp. Group | 6.7% | $113.19B |
| 4 | 4 | Humana Group | 6.6% | $110.55B |
| 5 | 5 | Elevance Health Inc. Group | 6.4% | $108.18B |
| 6 | 6 | Kaiser Foundation Group | 6.0% | $100.96B |
| 7 | 7 | HCSC Group | 3.8% | $64.07B |
| 8 | 8 | Cigna Health Group | 2.5% | $41.92B |
| 9 | 9 | Molina Healthcare Inc. Group | 2.1% | $35.84B |
| 10 | 10 | Guidewell Mutual Holding Group | 1.8% | $30.71B |
Source: National Association of Insurance Commissioners, NAIC 2024 Market Share Reports For the Top 125 Accident and Health Insurance Groups and Companies. Values reflect the current dataset, refreshed as new NAIC filings are processed. National Association of Insurance Commissioners, NAIC 2024 Market Share Reports For the Top 125 Accident and Health Insurance Groups and Companies. Values reflect the current dataset, refreshed as new NAIC filings are processed.
Findings
Top entity in the ranking
The top-ranked record in this dataset is UnitedHealth Group, with a market share of 16.1% and direct written premium of $269.45B. The full top-10 set is rendered in the table above. When National Association of Insurance Commissioners publishes a revision, the ranking and the prose around it update automatically.
Distribution shape
The gap between the top-ranked record (16.1%) and the 10th-ranked record (1.8%) characterizes how concentrated the top of the distribution is. The top 10 companies together hold roughly 59.3% of the national accident-and-health market, out of 125 rated companies total. The full distribution beyond this top-10 cut is summarized in the aggregate context section below.
Aggregate context
Across the full 125-company population behind this ranking, total direct written premium sums to $1588.52B and total market share sums to 94.6% (the remainder reflects carriers below the rated cutoff). The methodology page documents the exact filter applied (records with null or zero values on the ranking metric are excluded). This aggregate row is computed from the same dataset that powers the ranking above.
Source provenance
The records in this ranking originate from National Association of Insurance Commissioners, specifically the NAIC 2024 Market Share Reports For the Top 125 Accident and Health Insurance Groups and Companies. Plaininsurer ingests the source vintage published by the agency and keeps this page current, there is no static export carrying stale numbers, and a newly published dataset is reflected here within hours. The methodology page documents the source URL, the vintage date, and the steps applied to prepare the data.
Why this ranking matters
Rankings like this one let a reader scan a population quickly and identify outliers, concentrations, and patterns that warrant deeper investigation. The methodology page explains how a carrier earns inclusion in the dataset and how the ranking column is computed at the source. Readers deciding between health carriers should pair this size ranking with independent financial-strength ratings and PlainInsurer's claim denial-rate rankings -- market share measures scale, not claims-paying ability or service quality.
What this analysis cannot tell us
NAIC market-share figures combine filings from Property/Casualty, Life/Health, and Health annual statement filers so the accident-and-health (A&H) market can be seen in its entirety -- a single named group (e.g. a Blue Cross Blue Shield licensee) can carry business across more than one of those statement types, and NAIC's own rollup consolidates to the group level where that relationship is on record. Market share is computed from NAIC Annual Statement filings for the displayed data year (2024, published 2025) and lags current market conditions. State-specific and regional health plans (many California and Northeast entries in this ranking) compete on a very different footing than the national carriers above them; comparing a regional plan's rank directly against a national carrier's without accounting for that difference in addressable market can be misleading. Claims-paying ability, financial strength ratings, and policyholder complaint or denial-rate history are not captured by national market share; consumers should consult PlainInsurer's complaint and denial-rate rankings, independent rating agencies, and their state insurance commissioner for those dimensions.
Secondary cut from the same source
Direct written premium (millions of dollars) for ranks 11-20
Sources
- NAIC Annual Statement Database - https://content.naic.org
- NAIC 2024 Market Share Reports For the Top 125 Accident and Health Insurance Groups and Companies - https://content.naic.org/sites/default/files/publication-msr-hb-accident-health.pdf