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 cases, your vehicle damage when the driver who caused the accident either has no insurance or doesn't carry enough to cover your losses. Rather than leaving you to sue an uninsured driver — often an exercise in futility — this coverage steps in through your own policy.
UM and UIM are often sold together but are technically separate coverages. Some states split them further into bodily injury (UM/UIM BI) and property damage (UM/UIM PD) components, each with its own limit.
Why the Other Driver's Insurance Isn't a Guarantee
Most drivers assume that if someone else causes an accident, that person's liability insurance will cover the bill. In straightforward cases, that's true. But two common scenarios break this assumption entirely: the at-fault driver has no insurance, or they carry coverage that isn't nearly enough to pay for serious injuries or vehicle damage.
According to the Insurance Research Council, roughly one in eight drivers on U.S. roads is uninsured at any given time — and that figure rises sharply in certain states. Underinsured drivers are even more prevalent, since many people carry only their state's minimum liability limits, which can be quite low. For a deeper look at what those minimums actually include, see state minimum auto insurance requirements.
Without UM/UIM coverage in your own policy, recovering compensation from an uninsured driver typically means filing a lawsuit — and if that driver has few assets, a judgment may be uncollectable. Your UM/UIM coverage bypasses that problem entirely.
1 in 8
U.S. drivers estimated to be uninsured
According to the Insurance Research Council's periodic studies on uninsured motorists in the United States.
Varies by state
Minimum liability limits — often $25,000 or less
Many states set per-person liability minimums at $25,000 or lower, which can be quickly exhausted by serious injury claims.
~29%
Uninsured driver rate in highest-exposure states
Some individual states see uninsured motorist rates approaching or exceeding 25–29%, according to Insurance Research Council estimates.
How UM and UIM Coverage Actually Work
When a covered accident occurs and the at-fault driver is uninsured or underinsured, you file a claim with your own insurer under your UM or UIM coverage. Your insurer then pays up to your policy's stated limits for qualifying losses.
Uninsured Motorist (UM) Coverage
UM coverage applies when the at-fault driver has zero liability insurance — including hit-and-run situations in most states (though some policies require physical contact between vehicles). It generally covers:
- Medical expenses and rehabilitation costs for you and your passengers
- Lost wages resulting from accident-related injuries
- Pain and suffering, in states and policies where this is included
- Vehicle damage, if your policy includes an uninsured motorist property damage (UMPD) component
Underinsured Motorist (UIM) Coverage
UIM coverage activates when the at-fault driver has liability insurance, but their limits run out before your losses are fully compensated. For example, if your medical bills total $80,000 and the at-fault driver's policy only covers $25,000, your UIM coverage can bridge that $55,000 gap — up to your own UIM limit.
UM/UIM and Your Health Insurance Aren't the Same
Health insurance may reimburse medical bills after an accident, but it generally won't cover lost income, pain and suffering, or property damage. UM/UIM coverage is designed to address the full scope of harm from an accident caused by an uninsured or underinsured driver — not just the hospital bill. These two forms of coverage serve different but complementary purposes.
For a broader view of how UM/UIM fits alongside other coverages, the auto insurance coverage types guide provides a useful overview.
Common Gaps Drivers Don't Realize They Have
One of the most frequent misunderstandings is assuming that health insurance will cover everything collision-related. Health insurance may pay medical bills, but it typically won't compensate for lost wages, pain and suffering, or vehicle repair costs. UM/UIM coverage addresses categories that health insurance simply doesn't touch.
Another overlooked gap: low UM/UIM limits that don't match a driver's liability limits. If you carry $100,000 per person in liability coverage but only $25,000 in UM/UIM, a serious accident involving an uninsured driver leaves you significantly exposed. A symmetrical approach — matching your UM/UIM limits to your liability limits — is a widely cited best practice among insurance professionals.
Match Your UM/UIM Limits to Your Liability Limits
A practical rule of thumb: set your uninsured and underinsured motorist limits at the same level as your liability coverage. If you carry $100,000/$300,000 in liability, consider matching that in UM/UIM. This avoids an asymmetry where you're well-protected against claims others make against you, but poorly protected when the other driver is the problem.
Drivers who have only liability-only policies face an even starker exposure. Understanding what each coverage tier actually includes — and leaves out — is essential. The article on liability vs. full coverage breaks down exactly where those gaps fall.
For a structured look at how your personal situation should shape your overall coverage choices, see evaluating how much auto insurance coverage you need.
What to Check on Your Current Policy
Reviewing your declarations page — the summary document your insurer provides each policy term — is the fastest way to see what UM/UIM protection you currently carry. Look for these line items:
- UM/UIM Bodily Injury (BI): Covers injuries to you and your passengers. Expressed as per-person and per-accident limits (e.g., $50,000/$100,000).
- UM/UIM Property Damage (PD): Covers vehicle damage from an uninsured driver. Not included in every state or policy.
- Stacking vs. non-stacking: In states that permit it, stacking allows you to combine UM/UIM limits across multiple vehicles on the same policy, increasing the total available coverage.
If you're uncertain about your current protection or considering adjustments, consulting a licensed insurance agent is the appropriate next step — this article provides general educational information, not personalized insurance advice. You might also find it useful to review common mistakes drivers make when setting up auto insurance to avoid other coverage blind spots.
This article is for general informational purposes only and does not constitute personalized insurance, financial, or legal advice. Coverage terms, availability, requirements, and costs vary by state and insurer. Consult a licensed insurance professional and review your actual policy documents before making coverage decisions.