Uninsured and Underinsured Motorist Coverage: The Protection Most Drivers Overlook
Key Takeaways
Uninsured & Underinsured Motorist Coverage
Uninsured motorist (UM) and underinsured motorist (UIM) coverage are auto insurance protections that pay for your injuries and, in many states, your vehicle damage when the driver who caused the accident either has no insurance at all or carries limits too low to cover your losses. Rather than pursuing an at-fault driver who can't pay, you file a claim through your own policy. These two coverages are typically sold together and are often referred to collectively as UM/UIM.
UM/UIM coverage is legally required in roughly half of US states and optional in others; required limits vary significantly by jurisdiction. Some states split the coverage into separate bodily injury and property damage components with independent limits.
Why This Coverage Exists
Every state requires drivers who carry liability insurance to meet a minimum coverage threshold, but those minimums exist on paper — not every driver on the road actually complies. According to estimates from the Insurance Research Council, roughly one in seven drivers in the United States operates a vehicle without insurance. That means on any given road trip, a meaningful portion of the vehicles around you carry no financial protection for the people they might injure.
Even drivers who do carry insurance sometimes hold only the state-mandated minimums, which can be far below what a serious accident actually costs. A single emergency room visit, surgery, and weeks of physical therapy can easily exceed a policy with modest bodily injury limits. UM/UIM coverage was designed precisely for this scenario: to ensure that an innocent driver doesn't absorb losses caused by someone else's failure to carry adequate insurance.
For a broader look at how liability, collision, and comprehensive coverages each work, see our guide to what each coverage actually pays for.
~1 in 7
US drivers estimated to be uninsured
According to Insurance Research Council estimates, approximately 14% of US motorists operate without any auto insurance coverage.
~50%
States that mandate UM coverage
Roughly half of US states require drivers to carry uninsured motorist coverage, though required minimums and opt-out rules differ by jurisdiction.
How UM and UIM Coverage Work
Uninsured motorist (UM) coverage activates when the driver at fault has no insurance policy in force. You file a claim through your own insurer rather than through the at-fault driver's carrier — because there isn't one. Most UM policies cover bodily injury to you and your passengers; many also include uninsured motorist property damage (UMPD), which pays for your vehicle's repair or replacement.
Underinsured motorist (UIM) coverage steps in when the at-fault driver does have insurance but their limits are insufficient. For example, if a driver with $25,000 in bodily injury liability causes $80,000 in medical bills for you, your UIM coverage may pay the gap — up to your own UIM policy limit — after the at-fault driver's policy is exhausted.
Hit-and-run accidents occupy a gray area. In many states, UM coverage can apply to a hit-and-run where the at-fault driver fled and cannot be identified. However, states often require that there be physical contact between vehicles to trigger this benefit — the specific rules depend on your state and policy language.
Match Your UM/UIM Limits to Your Liability Limits
A common approach is to set your uninsured and underinsured motorist limits at the same level as your bodily injury liability limits. This creates symmetry — you're protected to the same degree that you protect others. Carrying the state minimum for UM/UIM while holding higher liability limits is a common and often overlooked gap.
It's worth understanding common auto insurance terms — including how limits and deductibles work — before evaluating your UM/UIM options.
What UM/UIM Typically Covers — and What It Doesn't
UM/UIM bodily injury coverage generally pays for:
- Medical expenses for you and your passengers
- Lost wages if injuries prevent you from working
- Pain and suffering (in states where this applies)
- Funeral expenses in fatal accident cases
Property damage coverage under UM/UIM (where available) typically pays to repair or replace your vehicle. However, not all states require insurers to offer UMPD, and some policies carry a separate deductible for the property damage component.
Common exclusions include damage caused by a driver who lives in your household (most policies exclude household members from UM claims), and scenarios where you were operating a vehicle not listed on your policy — though specifics vary. Many drivers discover such gaps only after an accident occurs, as discussed in our article on coverage gaps that leave drivers exposed after an accident.
State Requirements and Choosing Your Limits
Approximately half of US states mandate that insurers offer UM coverage, and many of those require drivers to carry it unless they explicitly reject it in writing. States like New York, North Carolina, and Illinois require UM coverage; others, such as Florida and Arizona, make it optional. For a reference on what your state requires, see auto insurance minimum requirements by state.
When selecting limits, a common guideline is to match your UM/UIM limits to your liability limits. If you carry $100,000/$300,000 in bodily injury liability, carrying the same in UM/UIM ensures your own protection mirrors what you extend to others. Carrying only the state minimum for UM/UIM while holding high liability limits creates an asymmetry that may leave you exposed.
Thinking about how UM/UIM fits into your overall policy structure? Our overview of full coverage vs. minimum coverage trade-offs can help frame those decisions.
This article is for general informational purposes only and does not constitute personalized insurance, legal, or financial advice. Coverage availability, requirements, and terms vary by state and insurer. Review your actual policy documents and consult a licensed insurance professional for guidance specific to your situation.