How is Medicare Advantage developing in Illinois?
Illinois's MA-and-other health plan share is 43.8% — below the 51.1% national share by 7.3 points, ranking 35 of 53 with 1,087,735 people in a Medicare Advantage or other Medicare health plan out of 2,480,946 Medicare beneficiaries, on the CMS state record for April 2026.
Share and enrollee counts are the CMS state record for April 2026 (Medicare Monthly Enrollment). Summing this state’s 102 county rows gives 43.9% on 2,478,650 beneficiaries, a difference of 2,296 beneficiaries CMS does not assign to a county. Both figures are published; the state record is canonical for the state. Dual counts are county-file aggregates.
Highest-penetration counties in Illinois
County table with momentum
| County | MA & other health plan share | YoY change | Enrollment growth | Medicare beneficiaries |
|---|---|---|---|---|
| Stephenson | 61.6% | +0.7 | +1.9% | 12,245 |
| Rock Island | 59.0% | +0.3 | +1.6% | 32,895 |
| Sangamon | 59.0% | +1.7 | +4.3% | 45,270 |
| Champaign | 58.8% | -0.3 | +1.2% | 33,267 |
| Winnebago | 58.7% | +0.9 | +2.8% | 63,506 |
| Jo Daviess | 58.1% | +0.5 | +1.8% | 6,940 |
| St. Clair | 56.0% | +0.4 | +2.2% | 54,179 |
| Vermilion | 56.0% | +0.3 | +0.7% | 17,811 |
| Madison | 55.4% | +0.7 | +1.7% | 59,730 |
| Piatt | 54.9% | -0.5 | -0.1% | 4,147 |
| Menard | 54.5% | +3.8 | +9.2% | 3,047 |
| Monroe | 54.2% | -0.6 | +1.4% | 8,633 |
| Boone | 52.6% | +0.7 | +3.8% | 11,025 |
| Randolph | 51.5% | +2.1 | +5.6% | 7,467 |
| Peoria | 50.9% | +0.6 | +1.9% | 38,151 |
| Douglas | 50.5% | +0.7 | +2.6% | 4,345 |
| Jackson | 50.3% | +1.6 | +4.3% | 11,091 |
| Henry | 48.3% | +0.6 | +2.2% | 12,343 |
| Mercer | 48.3% | -2.0 | -2.2% | 4,049 |
| Alexander | 48.2% | +4.1 | +7.1% | 1,493 |
| Ogle | 48.2% | +1.1 | +4.3% | 12,057 |
| Bond | 47.5% | +3.4 | +8.6% | 3,863 |
| Christian | 47.5% | +1.7 | +4.9% | 8,297 |
| Coles | 47.3% | +1.2 | +3.5% | 10,599 |
| Fulton | 47.2% | +2.6 | +6.5% | 8,437 |
Tracked carrier positions in Illinois
| Carrier | Enrollment (K) | Plans | Stars | YoY trend | Note |
|---|---|---|---|---|---|
| BCBS | 298 | 6 | 4 | +2.4% | Chicago and suburban IL |
| Humana | 168 | 5 | 3.5 | -4.1% | Chicago suburban markets |
Carrier coverage is the curated major-carrier extract (March 2026) — not all carriers in the state.
Sales playbook one-pager
The Illinois state sales playbook PNG has been withdrawn. It was rendered from the February 2026 enrollment file and carried a Growth Runway class, both retired by the 2026-08-24 data audit. Use the county explorer for April 2026 health plan share, momentum and market size, and the carrier battlecards for competitive facts. Read the audit.
So what / Now what Interpretation
Illinois is a switcher market — expansion means winning members from incumbent MA plans on benefits, network, and brand.
- Compare against neighboring states on the national table.
- Drill into the county table above; velocity, D-SNP share, and top-carrier columns show where and how growth is happening.
- Check 2026 plan exits for orphaned membership contestable in this market.
- Sales teams: rank this market on health-plan share headroom and momentum in the county explorer, and see which competitive facts apply on the carrier battlecards.
Provenance — MA enrollment & penetration by state
- Source file
- Medicare Monthly Enrollment (CCW-derived national, state and county beneficiary counts; data.cms.gov dataset
d7fabe1e-d19b-4333-9eff-e80e0643f2fd, public API) - Vintage
- April 2026
- Last updated
- July 31, 2026
- Refresh cadence
- Monthly (CMS publishes ~3 months in arrears)
- Method
- State-level rows pulled from the Medicare Monthly Enrollment API; MA share = MA_AND_OTH_BENES / TOT_BENES. Refreshed via automated pipeline from the CMS public API.
- Known limitations
- Health plan share here is measured against all Medicare beneficiaries (Parts A and/or B), not the KFF eligible-only basis, which runs ~4pts higher.