Updated July 2026
What Is Uninsured and Underinsured Motorist Coverage Insurance?
Uninsured motorist coverage (UM) pays your medical expenses, lost wages, and vehicle repair costs when an at-fault driver has no insurance. Underinsured motorist coverage (UIM) kicks in when the at-fault driver's liability limits are too low to cover your full damages. Both coverages protect you from paying out-of-pocket for someone else's mistake when that driver lacks adequate insurance.
- An uninsured driver runs a red light and T-bones your car. You suffer $30,000 in medical bills and $8,000 in vehicle damage. The at-fault driver has no insurance to pay your claim. Your UM coverage pays the full $38,000 minus your deductible, protecting you from filing a lawsuit against someone with no assets.
- A driver with Illinois's minimum $25,000 bodily injury limit rear-ends you at highway speed. Your medical bills total $60,000. The at-fault driver's liability policy pays its $25,000 limit, leaving you $35,000 short. Your UIM coverage pays the remaining $35,000, up to your policy limit, so you're not forced to sue the driver personally or drain your savings.
- An uninsured driver causes a chain-reaction crash involving your vehicle. Your injuries total $50,000, but the other insured drivers involved weren't at fault. Your UM coverage pays your $50,000 claim because the driver who caused the pileup had no insurance. Without UM, you'd be filing a lawsuit against an uninsured defendant with little chance of recovery.
Who Needs Uninsured and Underinsured Motorist Coverage Insurance?
Drivers who cannot afford to pay $30,000 to $100,000 out-of-pocket for medical bills and vehicle damage should carry UM/UIM at limits matching their liability coverage. If you're meeting Illinois's minimum liability requirement and no more, you're especially vulnerable—your own $25,000/$50,000 liability policy won't help you when an uninsured driver causes $60,000 in injuries to you.
Calculate what you'd pay out-of-pocket if an uninsured driver totaled your car and sent you to the ER tomorrow. If that number exceeds your liquid savings, carry UM/UIM at limits matching your liability coverage. If your health insurance has a high deductible or doesn't cover auto accidents fully, UM bodily injury coverage is non-negotiable.
How Much Does Uninsured and Underinsured Motorist Coverage Insurance Cost?
UM/UIM coverage typically adds $8 to $18 per month to an Illinois auto policy, or $96 to $216 annually, depending on your liability limits and whether you stack coverage across multiple vehicles.
- Your UM/UIM limits—most carriers offer limits matching your liability coverage, and higher limits cost more.
- Whether you select stacked or unstacked coverage—stacked UM/UIM multiplies your per-vehicle limit by the number of insured vehicles, increasing both protection and premium.
- Your ZIP code's uninsured driver rate—Cook County and East St. Louis areas see higher UM premiums due to elevated uninsured motorist rates.
- Your liability limits—because UM/UIM limits cannot exceed your liability limits in Illinois, drivers carrying $100,000/$300,000 liability pay more for matching UM/UIM than drivers with $25,000/$50,000.
- Claims history—filing a UM claim can raise your premium at renewal, even though you weren't at fault, because it signals higher risk exposure to your carrier.