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Uninsured/Underinsured Motorist Coverage: Why You Need It in 2026
By the PolicyZen Team · Updated March 2026 · 8 min read
About 1 in 8 drivers on American roads is uninsured — and millions more carry state-minimum coverage of $25,000 per person that won't cover a serious injury's medical bills, lost wages, or pain and suffering. If one of them hits you, your ability to recover financially depends almost entirely on whether you have uninsured/underinsured motorist (UM/UIM) coverage on your own policy.
UM/UIM coverage makes your own insurance company step in as if they were the at-fault driver's insurer — when that driver either has no insurance (UM) or insufficient insurance to cover your damages (UIM). It's one of the most cost-effective coverages in auto insurance, adding $50–$150/year for $100,000–$300,000 in coverage.
UM vs. UIM: The Difference
- Uninsured Motorist (UM): At-fault driver has NO insurance. Also covers hit-and-run accidents where the driver flees and is not identified. Required in many states.
- Underinsured Motorist (UIM): At-fault driver HAS insurance, but their liability limits are too low to cover your full damages. Your UIM steps in to cover the gap between their policy and your actual losses.
UM/UIM Bodily Injury vs. Property Damage
- UM/UIM Bodily Injury (UMBI/UIMBI): Medical expenses, lost wages, pain and suffering, disability — for you and your passengers. The critical coverage. Expressed as limits like 100/300 ($100,000 per person, $300,000 per accident).
- UM Property Damage (UMPD): Damage to your vehicle caused by an uninsured driver — typically a cheaper alternative to collision coverage for this specific scenario. Not available in all states.
How UIM Applies to a Real Claim
You're seriously injured. Medical bills: $180,000. Lost wages: $50,000. Total damages: $230,000. At-fault driver carries state minimum: $25,000 liability. Gap: $205,000.
If you have $250,000 UIM coverage, your insurer pays the $205,000 gap (after the at-fault driver's $25,000 is exhausted). Without UIM, you'd need to sue the at-fault driver personally — typically an unproductive exercise if they couldn't afford insurance.
State minimums for liability coverage range from $15,000–$30,000 per person — amounts that haven't kept up with medical inflation and won't cover a serious injury. Someone hitting you with minimum coverage is effectively underinsured for any significant accident. UIM exists precisely because most drivers carrying minimum coverage have $0 personal assets to pursue.
Stacked vs. Non-Stacked UM/UIM
In states that allow it, "stacked" UM/UIM means you can multiply your coverage limit by the number of vehicles on your policy. Two vehicles, each with $100K UM: stacked coverage = $200K per accident. Non-stacked: $100K limit regardless of vehicle count. Stacking costs more but provides significantly higher protection. Not all states allow stacking.
Frequently Asked Questions
What is the difference between uninsured motorist (UM) and underinsured motorist (UIM) coverage?
Uninsured motorist (UM) coverage pays when you're hit by a driver who has no liability insurance at all. Underinsured motorist (UIM) coverage pays when the at-fault driver has insurance, but their limits are too low to cover your full damages. They address different scenarios — many drivers carry both.
How many drivers on the road are uninsured?
According to the Insurance Research Council, approximately 1 in 7 drivers in the US (about 14%) are uninsured. In some states like Mississippi, Michigan, and Tennessee, the rate exceeds 20%. Being hit by an uninsured driver without UM coverage can leave you paying out of pocket for serious injuries and vehicle damage.
What is stacked vs. non-stacked UM/UIM coverage?
Stacking allows you to combine UM/UIM limits across multiple vehicles on your policy. For example, if you have two cars each with $100,000 UIM limits, stacked coverage would give you $200,000 of combined UIM protection per accident. Non-stacked limits are per vehicle, regardless of how many vehicles you insure. Stacking is available in some states but not others.
Does UM/UIM cover hit-and-run accidents?
UM coverage typically covers hit-and-run accidents — the fleeing driver is treated as an uninsured motorist. Requirements vary by state; some require physical contact between vehicles for hit-and-run UM claims. Review your policy's specific hit-and-run language and your state's rules.
How much UM/UIM coverage should I carry?
At minimum, match your UM/UIM limits to your auto liability limits. If you carry $300,000 in liability, carry $300,000 in UM/UIM. Higher limits — $500,000 or more — are recommended for households with significant assets, since the true cost of serious injuries (medical, lost wages, long-term care) can easily exceed $300,000 in a major accident.
Know Your Auto Coverage Limits
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