What is uninsured/underinsured motorist (UM/UIM) insurance and how does it protect you from other drivers?

Uninsured and underinsured motorist coverage is what protects you if you're hit by a driver who doesn’t have enough insurance — or any at all — to pay for the damage they caused. While these are two different types of protection, they are usually bundled together as a single add-on to your policy. 

Uninsured motorist (UM) covers your medical bills and vehicle repairs if the at-fault driver has no liability insurance or if you’re the victim of a hit-and-run. Underinsured motorist (UIM) steps in when the other driver has insurance, but their policy limits are too low to fully cover the cost of the accident. This is a common issue since many drivers only carry their state’s required minimum coverage. 

What is uninsured motorist coverage?

Uninsured motorist (UM) coverage applies when you’re in an accident caused by a driver who has no auto insurance at all. It also covers hit-and-run accidents, where the at-fault driver flees the scene and can’t be identified. By adding UM, you ensure that someone else's lack of coverage doesn't end up costing you.

There are two main types of uninsured motorist coverage. 

Uninsured motorist bodily injury (UMBI)

Uninsured motorist bodily injury (UMBI) covers injury-related expenses for you and your passengers if an uninsured driver causes a crash.

UMBI may help pay for:

• Medical bills and hospital stays
• Lost wages if you or your passengers can’t work due to injuries
• Pain and suffering
• Rehabilitation and ongoing care

UMBI is required in some states. Your coverage limits (the maximum your policy will pay) will typically match your liability limits. For example, if you have $100,000 per person, $300,000 per accident of bodily injury liability coverage, your UMBI limits would also be 100/300.

Uninsured motorist property damage (UMPD)

Uninsured motorist property damage (UMPD) covers repairs to your vehicle and any other property (like your house, garage, or fence) if it’s damaged by an uninsured driver. 

UMPD isn’t available in every state. In states where it is available, it might come with a deductible, which is a specific amount of damage you’re required to cover out of pocket. For example, in the event of an approved UMPD claim in Maryland, drivers are required to cover $250 of damage on their own. UMPD would cover the rest, up to your policy limits.

What is underinsured motorist coverage?

Underinsured motorist coverage applies when the at-fault driver has insurance, but their liability coverage limits aren’t high enough to fully pay for your medical bills or property damage. In these cases, the underinsured driver’s policy would pay up to its maximum, and your UIM coverage helps cover the gap.

Let’s say the at-fault driver has a state minimum liability policy with 25/50/25 limits. This represents $25,000 in bodily injury liability per person and $50,000 per accident, plus $25,000 per accident for property damage. They hit you, totaling your brand-new $60,000 car and injuring you and your passenger. Your medical bills total $75,000.

Since your claim exhausts both their bodily injury and property damage liability limits, your UIM coverage would kick in to pay the additional $10,000 in vehicle damage and $25,000 in medical bills, minus any applicable deductibles.

UM vs. UIM: Key differences at a glance

To make it easier to understand, here’s a quick comparison of underinsured and uninsured motorist coverage. 

Do you need UM/UIM insurance?

While liability insurance is required in 49 states, uninsured and underinsured motorist coverage (UM/UIM) is only mandatory in a few states, including Connecticut, Illinois, and Maryland. It’s optional in most states, leaving drivers to decide whether the added protection (and increased policy cost) is worth it.

Keep in mind that even if you have health insurance, it has limitations when you’re injured in a car accident. Health plans typically don’t cover pain and suffering or lost wages. They may even exclude certain rehabilitation costs, depending on your policy. And if you have a high deductible health plan, you could end up paying thousands out of pocket if you haven’t met your deductible.

UM/UIM fills in the gaps, providing financial protection when the at-fault driver's coverage isn’t enough or doesn’t exist. Although driving without insurance is illegal and can result in fines, jail time, and license suspension, the Insurance Research Council found about one in three (33.4%) drivers on the road in 2023 were uninsured or underinsured.

When to consider adding UM/UIM

You may want to add UM/UIM coverage to your auto insurance policy if:

• You live in a state with many uninsured drivers, like Mississippi (28.2%), New Mexico (24.1%), or the District of Columbia (23.1%).
• You want to financially protect your passengers in case they don’t have health insurance.
• You have high deductible health insurance and want coverage for medical expenses that your plan may not cover, or that require a high out-of-pocket payments before coverage kicks in.

How much coverage should you buy?

Most insurers suggest matching your UM/UIM limits to your liability limits. However, in 28 states, you can stack your coverage if you insure more than one car. This effectively multiplies your protection. For example, if you have two cars with $50,000 in coverage each, stacking lets you combine them for a total of $100,000 to use toward a single accident. This is a simple way to increase your payout potential after a serious crash with an uninsured driver.

Frequently asked questions

Is uninsured motorist coverage mandatory?

Requirements vary by state. Some states require insurers to offer UM coverage, while others require you to buy it unless you reject the coverage in writing. Check your state’s rules to find out whether UM is optional or mandatory.

Does UM coverage cover hit-and-runs?

Uninsured motorist bodily injury (UMBI) usually covers injuries from hit-and-run accidents, but uninsured motorist property damage (UMPD) may not apply in all states. Collision coverage is often required to repair your vehicle after a hit-and-run if you don’t have UMPD coverage. 

What is the difference between UM property damage and collision coverage?

Collision coverage pays to repair or replace your car no matter who is at fault, while UMPD only applies when an uninsured driver is responsible. UMPD may also come with a lower deductible.

Can I use my health insurance instead of UMBI?

Health insurance can cover some medical bills after an accident, but it doesn’t offer the broader protections UMBI does, such as lost wages, pain and suffering, or coverage for passengers.

Does UM/UIM cover me as a pedestrian?

Yes. UM/UIM typically follows the person, meaning it can protect you if you’re hit by another vehicle while walking, running, or riding a bicycle, not just when you’re driving a car.