Self-Funded vs. Fully Insured Health Plans: A Practical Guide for Mid-Sized Employers

If you run benefits at a company between 100 and 1,000 employees, there's a question that quietly shapes almost every other decision you'll make about healthcare: are you fully insured, or are you self-funded?

For most mid-sized employers, the answer is "fully insured" — usually by default, often without anyone ever consciously deciding. That made sense at one point. It frequently doesn't anymore. The economics, the regulatory environment, and the available infrastructure for self-funded plans have all shifted enough that organizations that wouldn't have considered self-funding ten years ago are now its biggest beneficiaries.

This guide walks through what each model actually is, how the financial mechanics work, where each one fits, what's changed in recent years, and how the choice between them affects every other benefit decision you make — including the increasingly important question of whether onsite primary care belongs in your stack.

The basic mechanics

In a fully insured health plan, the employer pays a fixed monthly premium to an insurance carrier. The carrier collects the premium and assumes the financial risk of the claims. If the workforce has a healthy year and claims come in low, the carrier keeps the difference. If the workforce has a rough year and claims exceed premium, the carrier absorbs the loss — and almost always raises premiums at renewal to recover the next year.

In a self-funded (also called self-insured) health plan, the employer pays claims directly as they're incurred, rather than paying a fixed premium to a carrier. The employer typically uses a third-party administrator, or TPA, to process claims, manage the network, and handle the day-to-day operations of the plan. To protect against catastrophic years, the employer also purchases stop-loss insurance — a separate policy that caps the employer's exposure on individual high claimants and on the plan's total annual claims.

The fundamental difference is who bears the risk. In a fully insured plan, the carrier owns the risk and earns a margin on it. In a self-funded plan, the employer owns the risk and keeps any savings — or absorbs any overruns — directly.

That single shift, from paying premiums to paying claims, changes almost everything about how an employer thinks about healthcare.

Why most mid-sized employers default to fully insured

Fully insured is the default for a few good reasons.

It's predictable. The employer knows what the plan costs every month. Budgeting is straightforward. There are no surprise spikes from a bad claims month. For a CFO who hates volatility, this matters.

It's simple. The carrier handles essentially everything. The employer's HR team doesn't have to think about claims processing, network contracts, stop-loss, or compliance with the alphabet soup of self-funded plan regulations. The benefits broker presents a few plan options at renewal, the company picks one, and life moves on.

It's familiar. Most brokers, especially those serving mid-sized employers, grew up selling fully insured plans. Self-funded conversations require a different skill set, and not every broker is equipped for them. The path of least resistance is to keep doing what's already working, even when it's not working as well as it could.

For very small employers — typically under 50 employees — these reasons are usually decisive. The mathematical case for self-funding is weak when claims volume is too small to be predictable. A single catastrophic claim can blow up a small group's year, and the stop-loss premiums required to protect against that scenario eat into the savings.

But the calculation looks different at 100 employees. It looks dramatically different at 250. By the time an employer hits 500 employees, fully insured is almost always the more expensive choice — and the gap only grows from there.

What self-funding actually saves

The savings from self-funding come from several distinct sources, and understanding them matters for evaluating whether the model fits your specific situation.

The carrier's margin. A fully insured premium includes the insurance carrier's profit, administrative overhead, taxes, and risk margin. Industry estimates put the loaded cost of these components at somewhere between 10% and 18% of the total premium. In a self-funded plan, this layer essentially disappears. The employer pays a TPA fee for claims administration — typically a fraction of what the carrier's full margin represents — and keeps the rest.

Premium taxes. Most states levy premium taxes on fully insured plans, typically in the 1.5% to 3% range. Self-funded plans, because they're regulated under federal ERISA rules rather than state insurance law, are generally exempt from these taxes. On a $5 million annual healthcare spend, that alone is $75,000 to $150,000 in savings.

ACA fees. Several Affordable Care Act fees apply differently to fully insured and self-funded plans, generally favoring self-funded.

Cash flow. In a fully insured plan, the employer prepays claims through monthly premiums. In a self-funded plan, the employer pays claims as they're incurred — meaning cash sits in the company's accounts longer before going out the door. For a growing organization, this working capital benefit is real, even if it doesn't show up on the benefits line.

Plan design flexibility. This is the savings line that most employers underestimate. A self-funded plan isn't constrained by the carrier's product menu. The employer can design the plan around its actual workforce — different deductibles, custom networks, carve-outs for pharmacy or behavioral health, direct contracts with high-quality local providers, point-solution integrations. Each of these design choices can drive meaningful savings, but they're only available in a self-funded structure.

Direct claims savings. This is the biggest category. In a fully insured plan, if the employer makes investments that reduce claims — wellness programs, biometric screenings, onsite primary care, disease management — the savings flow to the carrier in the form of a better loss ratio, and the employer sees the benefit only indirectly through (hopefully) a smaller renewal increase. In a self-funded plan, those same investments produce direct, immediate savings that flow straight to the employer's bottom line. This single distinction changes the entire economics of healthcare investment.

Add it all up, and a well-managed self-funded plan typically saves 8% to 15% over an equivalent fully insured plan in the first year, with savings growing in subsequent years as the employer fine-tunes plan design and adds programs that drive claims reductions.

What self-funding costs

Self-funding isn't free. The savings come with real responsibilities and real risks, and any honest evaluation has to weigh both sides.

Cash flow volatility. Even with stop-loss, claims arrive unevenly. A month with two large claims can spike the employer's healthcare spend significantly above the average. Most TPAs offer aggregate funding arrangements that smooth this out, but the underlying volatility is still real and requires a CFO who's comfortable with the model.

Administrative complexity. Self-funded plans require more active management than fully insured plans. Someone — internally or externally — needs to be looking at claims data, monitoring plan performance, evaluating programs, managing the TPA relationship, and ensuring compliance with ERISA, HIPAA, and other federal requirements. This is usually handled through a combination of an experienced broker, a TPA, and an internal benefits leader, but it's not zero-effort.

Stop-loss premiums. Stop-loss insurance protects the employer from catastrophic claims, but it costs money. Stop-loss premiums for mid-sized employers typically run somewhere between 10% and 25% of total expected claims, depending on workforce demographics, claims history, deductible level, and the specific risks being covered. This is a real line item, and it grows when the employer's claims experience is bad.

The lasering risk. Stop-loss carriers reserve the right to "laser" specific high-risk individuals at renewal — meaning they raise the deductible (or exclude coverage entirely) for an employee or dependent who is expected to generate large claims. This creates a real tail risk for self-funded employers and is one of the most important things to negotiate carefully in any stop-loss contract.

Fiduciary responsibility. Self-funded plans put the employer in a more direct fiduciary role under ERISA. This isn't catastrophic for most employers, but it requires attention. The employer can't just hand the plan to a carrier and forget about it.

For most employers above a certain size, these costs are manageable and well worth the savings. Below that size, the math gets harder. The threshold has dropped dramatically in recent years — from "you really need 1,000 employees" a decade ago to "100 employees is increasingly viable" today — but it hasn't disappeared.

Level-funded plans: the middle path

For employers who find pure self-funding too complex or too volatile, level-funded plans have emerged as a hybrid model that's become extremely popular in the mid-market.

In a level-funded plan, the employer pays a fixed monthly amount that includes claims funding, administrative fees, and stop-loss premiums. The plan is technically self-funded, but the employer's cash flow looks and feels like a fully insured arrangement. At year-end, if claims came in below expectations, the employer receives a refund of the unused claims fund. If claims exceeded expectations, the stop-loss coverage absorbs the difference.

Level-funded plans capture most of the benefits of self-funding — the ERISA preemption, the plan design flexibility, the data access, the upside when claims are favorable — while limiting the downside risk and smoothing the cash flow volatility that scares some employers away from full self-funding.

For employers in the 50 to 250 range, level-funded is often the right entry point into self-funding. It builds the muscles, generates the data, and lets the organization grow into a more sophisticated self-funded structure over time.

How this connects to onsite primary care (and why most onsite clinics don't make sense for fully insured employers)

Here's the connection most employers miss until someone walks them through it: the financial case for onsite primary care depends almost entirely on whether the plan is self-funded.

Onsite clinics save money primarily through claims avoidance — fewer ER visits, fewer specialty referrals, lower pharmacy spend, earlier intervention on chronic conditions, fewer catastrophic claims caught upstream. In a self-funded plan, every one of those savings flows directly to the employer's bottom line. Every avoided ER visit is real money the company doesn't spend that month.

In a fully insured plan, those same savings flow to the carrier. The employer might see some indirect benefit at renewal — might, depending on how the carrier prices it — but the immediate financial return is captured by the insurance company, not by the company that paid for the clinic.

This is why the onsite clinic industry, historically, has focused almost exclusively on self-funded employers. The math simply doesn't work the same way for fully insured plans. The clinic still delivers all the human benefits — better access, healthier employees, earlier detection, improved engagement — but the financial ROI either disappears or becomes much harder to quantify.

For mid-sized employers considering onsite care, this often means the conversation about clinics has to start with a conversation about funding model. An employer that is fully insured and considering an onsite clinic should usually evaluate self-funding (or level-funding) at the same time. The two decisions, taken together, can transform the economics of the benefits program. Taken separately, they often don't move the needle.

What's changed in recent years

The case for self-funding has strengthened significantly over the last decade for several reasons.

Stop-loss markets have matured. A wider range of carriers now serve the mid-market, with more flexible deductibles and better contract terms. Stop-loss for a 150-employee group is no longer a niche product.

TPAs have improved. A new generation of independent TPAs has built data and reporting capabilities that rival the big carriers. Mid-sized employers can now access detailed claims analytics, predictive modeling, and program ROI tracking that was previously only available to enterprise employers.

Level-funded plans expanded the on-ramp. What used to be a binary "are you self-funded or not" question now has a gradient. Employers can move incrementally from fully insured to level-funded to fully self-funded as they grow into the model.

Point solutions have proliferated. The ecosystem of vendors offering specialized programs — onsite clinics, virtual primary care, condition-specific programs, advanced primary care, direct contracting — is dramatically larger than it was ten years ago. These programs deliver their value almost exclusively to self-funded plans, which has pulled more employers toward self-funding to access them.

Carrier pricing has gotten less competitive. Fully insured premium increases have been outpacing claims trends in many markets, which has widened the gap between what fully insured employers pay and what self-funded employers actually spend. This gap is the single biggest driver of the migration toward self-funding.

How to think about the decision

For most mid-sized employers, the right framework looks something like this:

If you're under 50 employees, fully insured is usually the right answer. The volatility risk is real and the savings are typically not large enough to justify it.

If you're between 50 and 150 employees, level-funded is worth a serious look. It captures most of the benefits of self-funding with a meaningful reduction in administrative burden and cash flow risk.

If you're between 150 and 500 employees, self-funded or level-funded should be the default starting point, and fully insured should be the option that has to justify itself. The savings are usually significant. The infrastructure to support a self-funded plan at this size is widely available. The flexibility unlocks programs — onsite primary care chief among them — that aren't really available in a fully insured structure.

Above 500 employees, self-funded is almost always the right answer, and fully insured should generally only be considered when there's a specific reason it makes sense for that employer's situation.

These thresholds aren't bright lines. Workforce demographics, claims history, geography, industry, and organizational risk tolerance all matter. But the general arc is clear, and the gravitational pull toward self-funding for mid-sized employers has only gotten stronger over time.

The questions to ask before deciding

If you're evaluating a move from fully insured to self-funded, the questions that drive the right answer are:

What does our claims experience actually look like over the last three to five years, and what does the trend tell us? Most fully insured employers don't have full access to this data, but a good broker can request a claims experience report from the carrier that gives a directionally accurate picture.

What are our largest cost drivers, and could a self-funded structure address them? If pharmacy is your biggest issue, a carved-out PBM in a self-funded structure can save real money. If chronic conditions are driving claims, an onsite or near-site primary care program can deliver outsized ROI — but only in a self-funded structure.

What's our risk tolerance, and how would a bad year affect us? The worst-case scenarios in a self-funded plan are bounded by stop-loss, but the worst case still looks different from the predictable monthly premium of a fully insured plan.

Do we have the right broker and TPA partners, or do we need to upgrade? The single most common reason self-funded plans underperform is poor partner selection. The savings exist, but capturing them requires partners who know how to capture them.

What programs would we want to add that we can't add today? If onsite primary care, direct contracting, advanced primary care, or any of the other point solutions on the market are appealing, the funding model conversation has to come first.

The bottom line

Self-funding isn't right for every employer, but it's right for far more employers than currently use it. The mid-market migration from fully insured to self-funded has been one of the most important shifts in employer healthcare over the last decade, and it's still accelerating.

For employers thinking seriously about the future of their benefits program — particularly any employer considering onsite primary care, advanced primary care, direct contracting, or any other modern benefits innovation — the funding model conversation isn't a side topic. It's the foundation that determines whether everything else works.

Get the foundation right, and a whole category of programs becomes available that simply don't make sense in a fully insured world. Get it wrong, and you'll keep watching premiums climb while wondering why none of the wellness investments you've made seem to slow them down.

The math has changed. The infrastructure has changed. The available programs have changed.

For most mid-sized employers, the question is no longer whether self-funding is for companies your size. It's whether you're going to use the model that gives you the most control over your healthcare spend — and unlocks the benefits that actually move the needle.