Most people compare health insurance plans by looking at two numbers — the monthly premium and the deductible. But there’s a whole category of costs that insurers don’t always put front and centre, and discovering them after you’ve enrolled can be a genuinely unpleasant surprise.
I want to walk you through the hidden costs that are most likely to catch policyholders off guard, so you can factor them into your comparison properly and make an informed choice.
The Costs That Live in the Fine Print
Coinsurance After Meeting Your Deductible
Many people assume that once they’ve met their deductible, the insurance covers everything. That’s not how most plans work. After the deductible, you typically still pay a percentage of each claim — this is called coinsurance. A plan with 80/20 coinsurance means the insurer pays 80 percent and you pay 20 percent of covered costs after your deductible. If you have a major surgery costing £50,000 after your deductible, your 20 percent share is £10,000 — a figure that surprises many policyholders who thought they were fully protected.
Out-of-Network Balance Billing
This is one of the most financially damaging hidden costs in health insurance. When you receive care from an out-of-network provider, the insurer reimburses based on their ‘usual and customary’ rate for that service. The provider — who has no contractual agreement with your insurer — can then bill you for the entire difference between what the insurer paid and what they charged. This ‘balance bill’ can run into thousands of dollars for a single procedure. Regulatory protections against balance billing are improving in many jurisdictions but are not yet universal.
Facility Fees
Hospitals and healthcare facilities increasingly charge separate facility fees for the use of their premises, equipment, and staff — in addition to the professional fees charged by the physician. These facility fees can equal or exceed the physician fee itself, and they’re subject to separate deductibles and coinsurance calculations. A routine outpatient procedure that seems straightforward can generate multiple separate bills with multiple separate cost-sharing obligations.
Prescription Drug Cost Surprises
Tier Changes at Formulary Renewal
Drug formularies — the lists of medications covered by insurance plans — are reviewed and updated annually. A medication that was a low-cost generic in your tier-one level last year may be reclassified to a higher, more expensive tier at renewal. Or it may be removed from the formulary entirely. If you take regular medications, check the formulary at every renewal to confirm your drugs are still covered at the same tier and cost-sharing level.
Specialty Drug Cost Sharing
Specialty medications — biologics, disease-modifying drugs, and newer treatments for complex conditions — often fall into the highest formulary tier with coinsurance requirements rather than flat copayments. Twenty or thirty percent coinsurance on a specialty drug that costs thousands per month can translate into out-of-pocket costs that exceed what many people can afford even with insurance. Before starting any specialty medication, check your plan’s cost-sharing structure for that specific drug.
Administrative and Service Fees You Might Not Expect
Coordination of Benefits Confusion
If you’re covered by multiple health insurance plans — for example, your own employer plan and your spouse’s plan — the coordination of benefits process determines which plan pays first and how the second plan covers the remainder. This coordination isn’t always seamless, and administrative errors can result in delays, duplicated cost-sharing requirements, or claims falling between the two policies. Keep meticulous records when you’re covered by multiple plans.
Referral and Pre-Authorisation Costs
In HMO and some other plan types, seeing a specialist without a valid referral from your primary care physician means the claim may not be covered. Similarly, procedures that require pre-authorisation but are performed without it face rejection even when they’re medically necessary and covered under the policy. The hidden cost here isn’t a fee — it’s the full cost of a service you assumed was covered but wasn’t because a procedural step was missed.
Lifetime and Annual Benefit Limits on Specific Services
While the Affordable Care Act in the US and similar regulations in other jurisdictions eliminated lifetime dollar limits on most essential health benefits, limits on specific types of services — like mental health visits, physical therapy sessions, or chiropractic care — can still exist in some plans. A plan that covers twenty physiotherapy sessions per year sounds generous until you have a serious injury requiring forty sessions. Review the specific benefit limits for services you’re likely to need, not just the overall coverage structure.
Premium Increases at Renewal
Health insurance premiums don’t stay fixed. At each annual renewal, insurers adjust premiums based on age, claims experience, medical inflation, and changes in the plan’s actuarial performance. Premium increases of five to fifteen percent annually are common, and significantly larger increases occur in some markets and plan types. Factor in the trajectory of premium increases — not just this year’s cost — when evaluating the long-term affordability of a plan.
How to Uncover Hidden Costs Before You Enrol
Read the Summary of Benefits and Coverage document for every plan you’re comparing. This standardised document, required in many jurisdictions, discloses key cost-sharing information in a consistent format that makes comparison easier. Then go further — read the actual policy document or Evidence of Coverage to understand the sub-limits, exclusions, and procedural requirements that the summary document doesn’t always capture fully.
Call the insurer’s member services line with specific questions about the costs most relevant to your situation. Ask about your specific medications, your preferred providers, and any procedures you know you’ll need. Get the answers in writing where possible, because verbal representations that turn out to be incorrect can still result in unexpected bills that you’ll be responsible for paying.