Updated July 2026
What Is Uninsured and Underinsured Motorist Coverage Insurance?
Uninsured motorist coverage (UM) and underinsured motorist coverage (UIM) protect you when another driver causes an accident but can't pay for your damages. UM applies when the at-fault driver has no insurance at all. UIM applies when they carry insurance but their liability limits are too low to cover your medical bills, lost wages, or vehicle repair costs. Both coverages step in only after the at-fault driver's insurance is exhausted or confirmed absent — they don't replace your own collision or medical payments coverage.
- A driver with no insurance rear-ends you at a stoplight. You have $15,000 in medical bills and $8,000 in vehicle damage. Your UM bodily injury coverage pays the $15,000 medical costs up to your policy limit. If you added UM property damage, it covers the $8,000 vehicle repair after your deductible. Without UM coverage, you pay all $23,000 out of pocket or sue the driver personally — who likely has no assets to collect.
- A driver with Wisconsin's minimum $25,000 bodily injury limit causes a crash that leaves you with $60,000 in medical expenses and lost income. Their liability policy pays the $25,000 maximum. Your UIM coverage pays the remaining $35,000, up to your UIM limit. Without UIM, you absorb the $35,000 shortfall or pursue the driver's personal assets through court.
- An unidentified driver sideswiped your car on I-94 and fled. You have $4,500 in vehicle damage and $6,000 in medical bills. Your UM coverage treats the phantom driver as uninsured and pays both claims up to your limits, minus any applicable deductible. Without UM, your collision coverage handles the vehicle damage but leaves the medical bills unpaid unless you carry medical payments or personal injury protection.
Who Needs Uninsured and Underinsured Motorist Coverage Insurance?
You should carry UM coverage if you drive frequently in areas with high uninsured rates, commute on highways where hit-and-runs are common, or can't afford to cover a $30,000 injury out of pocket. It's especially valuable if you carry high liability limits — an uninsured driver who hits you won't match your coverage level, leaving you underprotected without UM.
Compare your health insurance deductible and out-of-pocket maximum to the cost of UM coverage. If your health plan leaves you with $5,000 or more in potential medical costs after an accident, UM coverage costing $12 per month is worth it. If you'd struggle to replace your car without insurance paying for it, add UM property damage — it's cheaper than a loan for a replacement vehicle.
How Much Does Uninsured and Underinsured Motorist Coverage Insurance Cost?
Uninsured motorist coverage typically adds $8 to $18 per month to your Wisconsin premium, or $96 to $216 annually, depending on your coverage limits and whether you add property damage protection.
- Your UM bodily injury limit — matching your liability limit costs more but closes the coverage gap if an uninsured driver causes serious injury.
- Adding UM property damage — Wisconsin allows this as an optional add-on, typically costing an additional $3 to $6 per month.
- Your county's uninsured driver rate — Milwaukee and Racine counties have higher uninsured rates, which can increase UM premiums by 10 to 15 percent.
- Stacking versus non-stacking — stacked UM coverage multiplies your limit by the number of vehicles on your policy, increasing cost but expanding protection.
- Your deductible on UM property damage — choosing a $250 deductible instead of $500 raises the monthly cost by roughly $2 to $4.