What Is UM/UIM Coverage and Why Does It Matter?

Uninsured motorist (UM) coverage pays for your injuries and damages when an at-fault driver carries no auto insurance at all. Underinsured motorist (UIM) coverage kicks in when the at-fault driver does have insurance, but their policy limits aren't high enough to cover your full losses. Together, UM/UIM is one of the most powerful — and often overlooked — protections you can add to your auto policy.

The numbers make a compelling case for carrying this coverage. According to the Insurance Research Council's 2025 study, 15.4% of U.S. motorists were uninsured in 2023 — that's more than 1 in 7 drivers on the road. Some states are far worse: Mississippi tops the list at around 28%, followed by Washington D.C. at over 25%, and New Mexico at nearly 25%. When you factor in underinsured drivers — those who carry just enough coverage to be legal but not nearly enough to pay for a serious accident — the protection gap becomes even wider.

What UM/UIM Coverage Protects You Against

UM/UIM coverage is designed to step in when the at-fault driver's insurance falls short — or doesn't exist at all. Here's what it covers:

• Uninsured drivers — Drivers who carry zero auto insurance
• Underinsured drivers — Drivers whose limits are too low to fully compensate your losses
• Hit-and-run accidents — In most states, a hit-and-run is treated as an uninsured motorist scenario, allowing you to file a UM claim
• Injuries to passengers — Your coverage extends to anyone riding in your vehicle at the time of the accident

Without UM/UIM coverage, your only recourse after being hit by an uninsured driver is to sue them personally — which rarely results in meaningful compensation since most uninsured drivers lack the financial assets to pay. Your health insurance may cover some medical bills, but it won't compensate you for lost wages, pain and suffering, or vehicle damage. Learn more about how personal injury protection and MedPay coverage compare as supplemental options for medical costs.

UMBI vs. UMPD: The Two Types of UM/UIM Coverage

Just like standard liability insurance, UM/UIM coverage is split into two distinct components — one for injuries and one for property damage.

Uninsured Motorist Bodily Injury (UMBI)

UMBI is the more critical of the two. It covers:

• Medical expenses for you and your passengers
• Lost income if injuries keep you out of work
• Pain and suffering damages
• Funeral costs in fatal accidents

UMBI typically has no deductible, making it very accessible when you need it most. Experts — including personal injury attorneys — consistently urge drivers to purchase UMBI limits that match their liability limits, since medical costs in a serious accident can easily exceed $100,000.

Uninsured Motorist Property Damage (UMPD)

UMPD covers repairs to your vehicle when an uninsured driver is at fault. However, it's more limited than UMBI in important ways:

• It may carry a small deductible (often around $200–$300)
• Some states do not offer UMPD, or may not extend it to hit-and-run claims
• Coverage is capped at the actual cash value of your vehicle

UMPD vs. Collision Coverage

If you already carry collision coverage on your vehicle, the role of UMPD becomes less urgent for property damage — but UMBI remains essential regardless. Here's how they compare:

If you have collision insurance, you may choose to skip UMPD for property damage — but you should still carry UMBI to protect against bodily injury losses that collision coverage doesn't touch.

Stacked vs. Unstacked Uninsured Motorist Coverage

In states where it's permitted, drivers with multiple vehicles have the option to stack their UM/UIM coverage. This is an important decision that can dramatically change how much protection you actually have.

What Is Stacking?

Stacking allows you to combine — or "stack" — the UM/UIM bodily injury limits from multiple vehicles on the same policy, or across multiple separate policies, to create a higher total coverage amount.

Example: If you insure two cars and each has $25,000 in UM/UIM coverage, stacking would give you a combined limit of $50,000 per accident instead of just $25,000.

There are two forms of stacking:

• Vertical (Intra-policy) stacking — Combines limits across multiple vehicles on the same policy
• Horizontal (Inter-policy) stacking — Combines limits from two or more separate policies

Stacking applies only to bodily injury coverage, not property damage.

Stacked vs. Unstacked: A Quick Comparison

UM/UIM Requirements by State & Coverage Costs

States Where UM/UIM Is Required

Twenty states plus the District of Columbia have mandatory requirements for uninsured or underinsured motorist coverage. This means insurers must include it in your policy unless you formally reject it in writing. States with mandatory UM/UIM include:

About half of all states require some form of UM/UIM. In states where it's optional, insurers must typically offer it — and you may be required to sign a written waiver if you decline.

Always check your state's current minimum car insurance requirements to understand what's mandatory where you live.

How Much Does UM/UIM Coverage Cost?

UM/UIM is widely considered one of the most affordable protections you can add to your auto policy. While exact costs vary by state, insurer, and your driver profile, industry figures typically place UM/UIM coverage at:

• $5–$10 per month for bodily injury coverage
• $2–$5 per month for property damage (UMPD) where available
• An estimated $50–$90 per year in combined UM/UIM premiums for many drivers

For context, this is a fraction of what you'd pay for full coverage car insurance, and the financial protection it delivers is disproportionately large compared to its cost.

Why Experts Strongly Recommend UM/UIM Coverage

Even in states where UM/UIM is entirely optional, virtually every insurance expert, financial advisor, and personal injury attorney recommends carrying it. Here's why:

The Risk Is Real and Growing

The uninsured driver rate in the U.S. has been climbing steadily since 2020, rising from roughly 11–12% pre-pandemic to 15.4% in 2023. In high-risk states like Mississippi, nearly 1 in 3 drivers you encounter could be uninsured. The odds are not in your favor.

Suing an Uninsured Driver Is Rarely Worth It

If an uninsured driver hits you and you don't have UM coverage, your legal options are limited. You can sue the driver personally, but most uninsured motorists don't have significant assets — meaning a judgment in your favor may never result in actual payment. You'd absorb the costs yourself.

It Fills Gaps That Other Coverages Can't

Health insurance may cover medical bills (with copays, deductibles, and coverage limits), but it won't pay for lost wages, pain and suffering, or vehicle damage. Liability car insurance only covers damage you cause to others — not what happens to you when someone else is at fault. UM/UIM is specifically designed to fill this gap. You may also want to consider umbrella insurance for an extra layer of liability protection on top of UM/UIM.

Hit-and-Runs Are a Real Threat

In most states, hit-and-run accidents are treated as uninsured motorist events. Without UM coverage, you have no recourse for injuries or vehicle damage if the driver flees the scene. The National Highway Traffic Safety Administration reports tens of thousands of hit-and-run crashes occur each year in the United States.

Understanding how UM/UIM fits into your broader policy is key. Review your no-fault insurance state rules if you live in a PIP state, as these systems interact with UM/UIM coverage in unique ways.

Frequently Asked Questions

Is uninsured motorist coverage the same as collision coverage?

No — they serve very different purposes. Collision coverage pays for damage to your vehicle in any crash, regardless of fault, including single-car accidents and hit-and-runs. Uninsured motorist coverage (specifically UMBI) primarily covers bodily injuries when you're hit by an uninsured or underinsured driver. UMPD covers vehicle damage from uninsured drivers but is narrower in scope than collision. If you have collision coverage, UMPD becomes less critical for property damage, but UMBI is still essential for injury protection.

Does UM/UIM coverage apply if I'm a pedestrian or cyclist?

Yes, in most cases. UM/UIM coverage typically extends to you as a policyholder even when you're outside your vehicle. If you're struck by an uninsured driver while walking, biking, or even riding in someone else's car, your own UM/UIM policy may cover your injuries. Policy terms vary, so confirm this with your insurer to understand the specifics of your coverage.

What happens if the at-fault driver has some insurance but not enough?

This is exactly what UIM (underinsured motorist) coverage is designed for. After the at-fault driver's liability coverage is exhausted, your UIM policy steps in to cover the remaining losses up to your own UIM limits. For example, if your damages total $80,000 and the at-fault driver only carried $30,000 in liability coverage, your UIM policy could potentially cover the remaining $50,000 — up to your policy's limit.

Should I match my UM/UIM limits to my liability limits?

Most experts strongly recommend it. Your liability coverage protects others from damages you cause; your UM/UIM coverage protects you from damages others cause. If you carry $100,000/$300,000 in bodily injury liability, it makes sense to match that with $100,000/$300,000 in UMBI. Carrying minimum UM/UIM limits while having high liability limits creates an asymmetric risk for you personally.

Will filing a UM/UIM claim raise my insurance rates?

In most states, filing a UM/UIM claim should not result in a premium surcharge because you were not at fault for the accident. However, policies and state laws vary. Some insurers may review your claims history during renewal. It's worth checking your policy language and asking your insurer directly — but fear of a rate increase should never stop you from using coverage you paid for.