Uninsured and Underinsured Motorist Coverage Explained

You can do everything right — buy solid liability limits, drive carefully, pay on time — and still get hit by someone carrying no insurance at all. A meaningful share of U.S. drivers are uninsured, and many more carry only bare-minimum limits that won’t cover a serious crash. Uninsured motorist coverage (UM) and underinsured motorist coverage (UIM) exist for exactly this scenario: they let your own policy step in when the at-fault driver can’t pay. Here’s how they work and why they deserve a place on your policy.

What Uninsured Motorist Coverage Is

UM coverage pays for *your* injuries and, in some states, *your car’s damage* when you’re hit by a driver with no insurance — or in a hit-and-run where the driver can’t be identified. Think of it as liability insurance you buy to protect yourself from other people’s irresponsibility.

Uninsured motorist coverage at a Glance

What is uninsured motorist coverage? Learn how UM/UIM protects you from uninsured drivers, what it costs, and how much you need. Below, we break down uninsured motorist coverage in detail so you can act with confidence.

Underinsured motorist coverage (UIM) is its close sibling: it kicks in when the at-fault driver’s liability limits are too low to cover your losses, filling the gap between their limits and your actual damages (up to your UIM limit).

Together, UM/UIM is the coverage that answers the question: “What happens to *me* if the other guy has nothing?”

The Two Parts: Bodily Injury and Property Damage

UM/UIM is typically split into two components, sold with separate limits:

• UMBI / UIMBI (bodily injury) — covers medical bills, lost wages, and pain-and-suffering compensation for you and your passengers when the at-fault driver is uninsured or underinsured. This is the critical half.
• UMPD / UIMPD (property damage) — covers repairs to your vehicle. Not all states offer this; where it’s unavailable, your collision coverage handles the car-repair side instead.

Limits are usually expressed like liability limits (e.g., 100/300), and many advisors suggest matching your UM bodily injury limits to your liability limits — the logic being that your family’s protection shouldn’t depend on a stranger’s insurance choices.

What UM/UIM Covers in Practice

• Medical expenses for you and your passengers after a crash with an uninsured or underinsured driver
• Lost wages if injuries keep you from working
• Pain and suffering compensation, similar to what you’d pursue from an at-fault driver’s liability policy
• Hit-and-run accidents — treated as uninsured motorist claims in most states (rules and requirements vary)
• Funeral expenses in fatal crashes
• Vehicle repairs where UMPD is available

It also typically covers you as a pedestrian or cyclist hit by an uninsured driver, and sometimes covers household family members even when they’re riding in someone else’s car — check your policy’s definitions.

Stacked vs Unstacked Coverage

In some states, if you insure multiple vehicles, you can choose stacked UM coverage, which combines the UM limits of all your vehicles into a larger pool available for a single accident. Unstacked coverage limits you to the per-vehicle limit. Stacking costs more but can substantially increase your protection — worth understanding if your state allows the choice.

Is UM/UIM Required?

It depends on the state. Many states require uninsured motorist coverage, some require underinsured as well, and a handful require neither. Even where it’s optional, it’s consistently recommended by consumer advocates because the risk it covers — an uninsured at-fault driver — is both common and financially devastating.

Where UM is mandatory, states set minimum limits, but those minimums are just a floor. Given how inexpensive UM/UIM typically is relative to the protection it provides, carrying higher limits is often one of the best values in auto insurance.

How Much UM/UIM Do You Need?

Consider these guidelines:

• Match your liability limits. If you carry 100/300/100 liability, carry 100/300 UM bodily injury. Your protection shouldn’t be weaker than the protection you provide others.
• Think about your health insurance gaps. High deductibles, copays, and lost-wage exposure make stronger UM bodily injury limits more valuable.
• Don’t skip it to save a few dollars. UM/UIM is generally one of the cheaper coverages on a policy — cutting it saves little and gambles a lot.

UM vs Collision and Health Insurance

These coverages overlap at the edges, so here’s the distinction:

• Collision repairs your car regardless of fault but doesn’t cover injuries and comes with a deductible.
• Health insurance covers medical bills but not lost wages or pain and suffering, and comes with its own deductibles and copays.
• UM/UIM is the only one that replicates what the at-fault driver’s liability *should* have paid — injuries, wages, and suffering together, with no deductible on the bodily injury portion in most states.

They complement each other; none fully replaces the others.

Frequently Asked Questions

What is uninsured motorist coverage in simple terms?

It’s coverage on your own policy that pays for your injuries (and sometimes car damage) when the driver who hit you has no insurance — or fled the scene. Underinsured motorist coverage does the same when their limits are too low.

Does UM cover hit-and-run accidents?

In most states, yes — hit-and-runs are treated as uninsured motorist claims. Some states require evidence of contact with the unknown vehicle or a police report within a set time, so report promptly.

Is uninsured motorist coverage worth it if I have health insurance?

Yes. Health insurance doesn’t cover lost wages, pain and suffering, or your passengers’ full losses, and it comes with deductibles and copays. UM fills those gaps and is typically inexpensive.

What’s the difference between uninsured and underinsured motorist coverage?

Uninsured applies when the at-fault driver has no insurance at all; underinsured applies when they have some, but not enough to cover your damages. Most policies bundle them together.

How much uninsured motorist coverage should I carry?

A common recommendation is to match your liability limits — for example, 100/300 UM bodily injury alongside 100/300 liability. It’s generally affordable, so buying robust limits is cost-effective protection.

The Bottom Line

You can’t control whether the driver who hits you bothered to buy insurance — but uninsured motorist coverage means you don’t have to. It’s inexpensive, it protects your family in one of the most unfair scenarios on the road, and it’s required in many states for good reason. When you’re building your policy, treat UM/UIM bodily injury limits as equal in importance to your liability limits, and compare quotes — because insurers price this valuable coverage very differently.

Want the full picture on uninsured motorist coverage? Start with the Insurance Information Institute’s coverage guide for the official rules, then work through the related guides below for practical uninsured motorist coverage money-saving steps.