Two Letters Apart, Two Different Problems
People say "UM/UIM" in one breath, but uninsured motorist (UM) and underinsured motorist (UIM) coverage respond to two different situations. Knowing the difference is how you make sure you're actually protected against both — because carrying only one leaves a real gap.
Uninsured Motorist (UM): They Had Nothing
UM coverage applies when the at-fault driver has no liability insurance at all:
- A driver who never bought a policy
- A driver whose coverage lapsed for non-payment
- In most states, a hit-and-run driver who's never identified
Example: An uninsured driver runs a red light and injures you. There's no policy to collect from — so your UM coverage pays your medical bills, lost wages, and pain, up to your UM limit.
Underinsured Motorist (UIM): They Didn't Have Enough
UIM coverage applies when the at-fault driver has insurance, but not enough to cover your losses.
Example: A driver causes a crash that leaves you with $80,000 in medical bills, but they carry only the $25,000 state minimum. Their policy pays $25,000 — and your UIM coverage fills the remaining $55,000, up to your UIM limit. Without UIM, that $55,000 is yours.
Why You Need Both
UM and UIM cover the two most common ways an at-fault driver leaves you holding the bill: they had nothing, or they had too little. Both happen constantly given how many drivers are uninsured or carry minimum limits. A complete auto policy carries both, ideally at limits matching your real exposure.
How the Limits Work
UM/UIM limits look like liability limits — for example, 100/300 ($100,000 per person / $300,000 per accident). A common recommendation is to match your UM/UIM limits to your liability limits, so you're as protected from others as you are protecting them.
A Quick Way to Remember
- UM = the other driver was uninsured (had nothing).
- UIM = the other driver was underinsured (had too little).
- You want both, because both situations are common — and expensive.
We help drivers confirm they carry both UM and UIM at sensible limits, and shop multiple carriers to price it well. [Check your coverage](/quote) to make sure you're covered for both.