Uninsured motorist (UM) insurance and underinsured motorist (UIM) insurance cover the injuries of you and your passengers if you're in a car accident caused by:

  • A driver who does not have any liability coverage.
  • A driver who does not have enough liability coverage to fully pay for your medical bills.

Depending upon your state, UM may also cover hit-and-run accidents.

Uninsured motorist insurance is also sometimes referred to as "uninsured motorist bodily injury insurance" (UMBI). Likewise, underinsured motorist insurance is sometimes referred to as "underinsured motorist bodily injury insurance" (UIMBI).

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

  • Uninsured motorist insurance covers you when another driver causes an accident and doesn't have any liability insurance.
  • Underinsured motorist insurance covers you when another driver causes an accident and has some liability insurance but not enough for all your medical bills.

What do uninsured motorist insurance and underinsured motorist insurance cover?

  • Medical expenses
  • Pain and suffering
  • Lost wages if you've been unable to work due to the accident

What does uninsured motorist property damage (UMPD) cover?

  • Damage to your vehicle
  • Damage to property such as your house or a fence

More: Stacked insurance: How to maximize an uninsured motorist claim

Is uninsured motorist coverage worth it?

UM is required in some states and optional in others.

The average for claim for UM bodily injury was $25,756 in 2012 , according to the National Association of Insurance Commissioners (NAIC).

If you don't have UM coverage and are injured in a car accident, your health insurance will pay medical bills. You might consider UM coverage if your health plan has a high deductible or high coinsurance. Also, your health insurance will not pay for lost wages or pain and suffering, which are generally covered by UM.

More: Compare car insurance

Is UMPD insurance worth it?

The national average for a UMPD claim was $1,539.94 in 2012, according to the NAIC. UMPD is not required in all states and what it covers differs by state. For example, in California, a hit and run driver must be identified for UMPD to provide coverage for damage.

If you already have collision insurance you might not need UMPD. Collision coverage will pay for damage to your vehicle no matter who caused it. However, UMPD is cheaper and usually has a lower deductible.

Fast facts: Uninsured motorists