C-SNP Enrollment Surges 49% as Medicare Advantage Restructures Around Special Needs Plans

From analyzing CMS enrollment files and plan-level benefit structures across three consecutive open enrollment periods, the C-SNP growth trajectory stands out as the single strongest structural shift in Medicare Advantage since the ACA standardized benefit categories. The 49% year-over-year enrollment surge is not a marketing-driven bump. It reflects a deliberate carrier strategy to pivot from broad-market general enrollment plans toward condition-specific products where risk adjustment revenue is higher, care management infrastructure creates defensible margins, and year-round enrollment through Special Election Periods provides a recruitment channel unavailable to standard MA plans.

ATI Advisory launched its public C-SNP enrollment and population dashboard on May 18, 2026, providing the first plan-level view into the demographic composition, risk profiles, and medical experience of C-SNP populations. KFF's 2026 Medicare Advantage enrollment spotlight confirmed what the ATI data revealed at the plan level: Special Needs Plans drove nearly all net enrollment growth in the program, with non-SNP general enrollment plans declining for the second consecutive year. The restructuring is no longer directional. It is measurable.

The 49% Enrollment Surge: What the Data Shows

C-SNP enrollment grew from approximately 1.1 million members in February 2025 to 1.6 million in February 2026, a 49% year-over-year increase that dwarfed every other MA product category (ATI Advisory, KFF). To put that growth in context: total Medicare Advantage enrollment grew by 1.1 million members (3%) during the same period, reaching 35.1 million. C-SNPs alone added roughly 500,000 of those members, accounting for nearly half of total program growth from a base of less than 5% of MA enrollment.

The plan count trajectory is equally striking. CMS approved 548 unique C-SNP plan options for 2026, up from 376 in 2025 (a 47% increase in plan count) and more than tripled from 165 plans in 2020 (KFF). Twenty-seven percent of C-SNPs offered in 2025 were new plans, meaning carriers are not simply relabeling existing products but launching purpose-built plan designs with condition-specific networks and benefit structures (HealthWorksAI).

The growth acceleration is recent. Between 2016 and 2022, C-SNP enrollment grew at just 3.8% annually, compared to 8.3% for overall MA enrollment (L.E.K. Consulting). The inflection began in 2024 when C-SNPs added 476,300 enrollees (71% increase), representing 75% of total SNP enrollment growth that year. The 2026 numbers confirm this was the start of a structural trend, not a one-year anomaly.

HealthScape Advisors' February 2026 analysis framed the shift starkly: total MA enrollment decelerated to 2.5% growth (down from 3.6% in 2025 and historic rates of 7% to 10% in the early 2020s), while 69% of MA plan leaders expect membership to remain flat or contract in plan year 2027. The era of broad-market MA growth is ending. What remains is growth concentrated in clinically targeted products.

Market Restructuring: SNPs Replace General Enrollment as the Growth Engine

The aggregate numbers tell the structural story. Over 8 million people were enrolled in Special Needs Plans as of February 2026, representing 23% of all MA enrollees, up from 21% in 2025 and 13% in 2018 (KFF). SNP enrollment increased by approximately 883,000 members (12.2% growth rate), comprising 83% of total MA enrollment growth.

Meanwhile, non-SNP individual MA plan offerings declined 9% to 3,373 plans, the second consecutive year of contraction following just a 1% decrease in 2025 (KFF). SNP plan options increased 19% over the same period to 1,721 total SNPs offered nationwide. The supply-side signal is clear: carriers are building more SNP products while actively pruning their general enrollment portfolios.

Original Medicare gained 600,000 members in 2026, reversing a multi-year decline trend (HealthScape). This reversal coincides with the 2.9 million forced disenrollments documented in the JAMA study, as carrier county exits and plan terminations pushed beneficiaries back to traditional fee-for-service coverage. The net effect is an MA program that grows modestly in total but reshapes dramatically in composition: fewer general enrollment members, more clinically segmented SNP enrollment, and a growing share of the Medicare-eligible population returning to Original Medicare rather than joining broad-market MA.

C-SNPs vs. D-SNPs: Two Diverging Growth Trajectories

The three SNP categories serve distinct populations and operate under different regulatory frameworks, producing very different growth dynamics in 2026.

Dual-Eligible SNPs (D-SNPs) remain the largest SNP category by enrollment, with 1,019 plans serving roughly 6.0 million members (KFF). D-SNPs added 344,000 members in 2026 (5.7% growth), an acceleration from the 219,000 additions (3.8% growth) in the prior year. D-SNPs target Medicare beneficiaries who are also eligible for Medicaid, integrating benefits across both programs. New CMS integration requirements, including FIDE and HIDE compliance standards, have slowed D-SNP expansion by raising operational and regulatory complexity for plan sponsors.

Chronic Condition SNPs (C-SNPs) added approximately 500,000 members (49% growth), making them the faster-growing segment for the first time. C-SNPs target beneficiaries with one or more of 15 CMS-approved chronic conditions (plus five approved multi-condition groupings), and they are not subject to the same Medicaid integration requirements that constrain D-SNP growth. This regulatory asymmetry, combined with elevated risk adjustment revenue and year-round enrollment access, makes C-SNPs increasingly attractive to carriers seeking MA growth without the dual-eligible administrative overhead.

Institutional SNPs (I-SNPs) serve beneficiaries in institutional settings such as skilled nursing facilities. I-SNP plan count declined slightly from 160 to 154 in 2026, and enrollment growth remains modest. The institutional setting limits the addressable market and requires specialized provider network configurations that few carriers have built.

The D-SNP and C-SNP growth stories are complementary but distinct. D-SNP margins run approximately 7.5% versus 3.6% for standard MA plans (MedPAC), driven by Medicaid cost-sharing subsidies and higher risk scores. C-SNP margins derive from elevated risk adjustment coefficients for chronic conditions and the ability to build condition-specific care management programs that reduce avoidable hospitalizations. Together, the two SNP categories are absorbing growth that general enrollment plans can no longer generate, but they require fundamentally different actuarial pricing, network design, and regulatory compliance approaches. For more on the D-SNP growth trajectory and its margin dynamics, see our companion analysis.

Condition Concentration: 97% of Enrollment in Three Categories

Despite CMS approving 15 chronic condition categories and five multi-condition groupings for C-SNP targeting, the market is overwhelmingly concentrated in cardiovascular-related conditions. Over 95% of C-SNP enrollment is in plans targeting diabetes mellitus, chronic heart failure, cardiovascular disorders, or combinations of the three (Milliman).

Milliman's 2024 market landscape analysis found that the cardiovascular/CHF/diabetes grouping alone had 205 plans with 598,924 enrollees, representing 85.3% of total C-SNP enrollment. That is more than 10 times the enrollment of the next-largest condition category. Plans targeting chronic lung disorders, end-stage renal disease, and chronic mental health conditions exist but at much smaller scale.

Seven of the 15 CMS-approved conditions have zero C-SNP plans targeting them, including cancer, autoimmune disorders, stroke (as a standalone condition), neurologic disorders, severe hematologic disorders, end-stage liver disease, and HIV/AIDS. The concentration reflects both the size of the eligible population (over 37 million Medicare beneficiaries have at least one cardiovascular condition) and the actuarial economics: cardiovascular conditions generate predictable, recurring utilization patterns that lend themselves to capitated risk management, while conditions like cancer produce volatile, episodic cost distributions that are harder to price under MA's prospective payment model.

This concentration creates a meaningful pricing question. CMS uses a single set of elevated age/sex risk score coefficients for all C-SNP enrollees regardless of the targeted condition. A 65-year-old female new to Medicare receives a risk score of approximately 0.900 in a C-SNP versus 0.532 in a general enrollment plan, roughly a 70% increase in risk-adjusted revenue (Milliman). But the actual cost profile varies substantially by condition. Plans targeting CHF and diabetes have well-documented utilization patterns with established care management protocols. Plans targeting conditions with thinner enrollment history carry more actuarial uncertainty per dollar of risk adjustment revenue received.

Carrier Market Share: UnitedHealth, Humana, and Elevance Dominate

C-SNP growth is not evenly distributed across carriers. The top three organizations command roughly three-quarters of the market, and the growth is accruing disproportionately to carriers that have made strategic bets on SNP expansion.

UnitedHealth Group holds 51% of C-SNP enrollment and 40% of all SNP enrollment (KFF). UHG lost 530,000 total MA enrollees in 2026 but added 267,000 in SNPs, illustrating the portfolio rebalancing underway: general enrollment contraction offset by targeted SNP growth. UHG's scale advantage in provider contracting, pharmacy benefit management through Optum Rx, and value-based care delivery through Optum Health gives it a structural edge in building the integrated care management infrastructure that C-SNPs require.

Humana holds 20% of C-SNP enrollment and captured the largest absolute growth, with C-SNP membership increasing 53% year-over-year. Humana added 1.2 million total MA enrollees (21% growth) in 2026, making it the single largest net gainer in the program. Humana's CenterWell primary care platform provides the vertically integrated care delivery model that supports condition-specific clinical pathways for C-SNP populations.

Elevance Health (Anthem/Wellpoint) grew its C-SNP enrollment by 12%, rounding out the top three with a combined market share of approximately 76% (KFF, HealthScape). UHG and Humana together control 54% of total SNP enrollment across all three categories.

Smaller and regional carriers are building C-SNP presence as well. SCAN, Alignment Health Plan, and Bright Health have established footholds in specific geographic markets. Zing Health and Gold Kidney Health Plan target specialized chronic condition populations with focused care models. Devoted Health doubled its total MA membership with 120% growth, though from a smaller base. The competitive dynamic mirrors what happened in D-SNPs five years earlier: national carriers establish market position early, build the clinical and administrative infrastructure, and create scale barriers that become increasingly difficult for later entrants to overcome.

Risk Adjustment Under Full CMS-HCC V28 Implementation

Plan year 2026 marks the first year of full V28 risk adjustment implementation, with no blending of the prior V24 model. The transition has significant implications for C-SNP financial performance.

V28 expanded the number of hierarchical condition categories from 86 to 115, organized into 26 disease families, while reducing the number of eligible ICD-10 diagnosis codes from 9,797 to 7,770 (CMS). The model was built natively on ICD-10 data rather than crosswalked from ICD-9 as V24 was, and it introduced "constraining," a methodology where related HCCs receive identical coefficient values to prevent double-counting of clinically overlapping conditions.

For C-SNPs, the V28 transition creates both opportunity and risk. The expanded HCC count captures more granular condition severity, which should benefit plans enrolling members with well-documented chronic conditions. But the ICD-10 code reduction eliminates over 2,000 diagnosis codes that were previously eligible for risk score credit under V24. Plans that relied on broad coding capture from chart reviews and health risk assessments will see lower incremental risk score value per encounter under V28.

CMS projects that V28 will reduce average MA risk scores by 3.12%, representing approximately $11 billion in net savings to the Medicare Trust Fund (Milliman). C-SNPs partially offset this through the elevated age/sex risk score coefficients that CMS applies to new-to-Medicare C-SNP enrollees. The 70% risk score premium for C-SNP members versus general enrollment (0.900 vs. 0.532 for a 65-year-old female) translates directly into higher per-member capitated revenue, creating a financial buffer against the aggregate V28 reduction.

The CMS decision to retain the 2024 risk model calibration rather than updating to 2023/2024 data preserved approximately 2.2 points of MA payment for the 2027 bid cycle. For C-SNP actuaries pricing the 2027 plan year, this deferral creates a favorable revenue baseline. But it also introduces model uncertainty: the risk scores were calibrated on a population mix that predates the C-SNP enrollment surge, meaning the model may not accurately reflect the cost patterns of the rapidly growing C-SNP population. Actuaries building 2027 C-SNP bids need to stress-test their projections against both the current V28 coefficients and the potential recalibration impact when CMS does update the model.

Benefit Design, SSBCI, and the Model of Care Mandate

C-SNPs operate under benefit design requirements that distinguish them from both standard MA plans and D-SNPs. CMS mandates that every C-SNP develop and implement a Model of Care (MOC), a structured framework for delivering condition-specific care coordination, care transitions, and health risk assessment. Each C-SNP member must receive an annual Health Risk Assessment (HRA) that evaluates clinical, functional, and social needs.

Approximately three-quarters of C-SNPs charge zero premiums (Milliman 2024 data), competing on benefit richness rather than price. This zero-premium strategy is sustainable because C-SNPs receive higher risk-adjusted revenue per member, allowing them to fund richer benefits while maintaining actuarial equivalence at the bid level. L.E.K. Consulting estimates that risk-adjusted capitated payments for C-SNP members run approximately 1.5 to 2 times the average MA member, creating substantial benefit funding capacity.

SNPs offer meaningfully richer supplemental benefits compared to general enrollment plans. KFF's 2026 analysis found that SNPs provide transportation benefits in 67% of plans (versus 24% for non-SNPs), over-the-counter allowances in 94% (versus 66%), bathroom safety devices in 47% (versus 21%), in-home support services in 25% (versus 7%), and caregiver support in 16% (versus 5%).

C-SNPs may also offer Special Supplemental Benefits for the Chronically Ill (SSBCI), a benefit category that CMS introduced to address the non-medical needs of high-acuity members. SSBCI eligibility requires that the enrollee have a medically complex chronic condition, face high hospitalization risk, and need intensive care coordination. Average annual SSBCI benefit limits run $980, with a range from $300 to $3,800 (HealthScape). Common SSBCI offerings include food and produce allowances, pest control, structural home modifications, and general living supports. Beginning January 1, 2026, CMS requires MAOs to send mid-year notifications between June 30 and July 31 to enrollees with unused supplemental benefits, a requirement that increases administrative costs but should improve benefit utilization rates.

Year-Round Enrollment: The Special Election Period Advantage

One of the most significant structural advantages C-SNPs hold over standard MA plans is year-round enrollment access. Beneficiaries with qualifying chronic conditions can enroll in a C-SNP at any time through a Special Election Period (SEP), bypassing the standard Annual Election Period (October 15 to December 7) that constrains general enrollment plan growth. The enrollee's physician must verify the chronic condition within 60 days of the enrollment start date.

This year-round enrollment window fundamentally changes the competitive dynamics. Standard MA plans compete for members during a seven-week open enrollment window, concentrating marketing spend and broker commissions into a narrow seasonal period. C-SNPs recruit continuously, spreading acquisition costs across twelve months and capturing members at the point of clinical need rather than during an arbitrary calendar window. For actuaries, the SEP creates a different enrollment pattern: C-SNP new member additions are distributed throughout the year rather than concentrated in January, which smooths the incurred claims curve and reduces the severity of anti-selection risk that typically accompanies mid-year enrollment (since the chronic condition must be clinically verified rather than self-reported).

Why This Matters for Actuaries

The C-SNP enrollment surge has direct implications across several actuarial domains.

Pricing and bid strategy. C-SNP bids require fundamentally different assumptions than general enrollment MA bids. The member population has higher baseline acuity, more predictable utilization patterns for the targeted conditions, and lower voluntary disenrollment rates. Actuaries building C-SNP bids need to model condition-specific cost distributions rather than relying on community-rated MA trend factors. Milliman recommends analyzing historical chronic-condition population performance, studying Medicare FFS data by service area, quantifying member migration impacts on medical loss ratios, and conducting detailed pharmacy analyses specific to the targeted conditions.

Risk adjustment modeling. The full V28 implementation changes the risk score arithmetic for chronic condition populations. Actuaries must recalibrate their coding intensity assumptions, particularly for plans that previously relied heavily on chart review-based diagnosis capture. The CMS ban on unlinked chart review diagnoses compounds this pressure, reducing the incremental risk score value of retrospective documentation efforts. C-SNP actuaries should model their risk score projections using the constrained V28 coefficients and the reduced ICD-10 code set rather than extrapolating from V24-era coding performance.

Network adequacy and provider contracting. C-SNPs require condition-specific provider networks that include specialists, care coordinators, and social service providers aligned with the targeted chronic conditions. The network design directly affects the Model of Care compliance and the plan's ability to deliver the clinical outcomes that justify the elevated risk adjustment revenue. Actuaries setting network adequacy assumptions need to account for the narrower specialist requirements and the higher per-member care coordination costs that C-SNPs carry relative to general enrollment plans.

Competitive intelligence and market entry. With 76% of the C-SNP market held by three carriers, new entrants face significant scale disadvantages in provider contracting, care management infrastructure, and brand recognition among the eligible population. Actuaries evaluating C-SNP market entry should stress-test their projections against aggressive competitor pricing, the risk of adverse selection if their plan attracts members with conditions outside the dominant cardiovascular/diabetes concentration, and the capital requirements for building the Model of Care infrastructure before the plan generates sufficient enrollment to achieve actuarial credibility. CMS has indicated it is monitoring C-SNP enrollment patterns among dual-eligible beneficiaries, signaling potential regulatory changes that could affect plan design flexibility.

The broader trajectory is clear. Medicare Advantage is evolving from a broad-market managed care alternative to Original Medicare into a portfolio of clinically segmented products where the actuarial value proposition is built around condition-specific risk management. The carriers that build the clinical infrastructure, achieve the Star Ratings performance necessary for quality bonus payments, and maintain pricing discipline under full V28 risk adjustment will define the next phase of the program. C-SNPs are not a niche product category. They are becoming the structural center of Medicare Advantage growth.