Health insurance shopping usually presents a menu of plans trading a lower monthly premium for a higher deductible, or vice versa. The math behind that trade-off is straightforward once you separate two different questions: what can you afford monthly, and what could you actually afford to pay out of pocket in a bad year?
The trade-off, in plain terms
A high-deductible plan might save you $150/month in premium compared to a low-deductible plan, but require you to pay the first $5,000 or more of care yourself before the plan starts covering much. That's a great deal if you rarely use healthcare and can comfortably absorb a $5,000 hit in a bad year. It's a bad deal if a $5,000 bill would mean high-interest debt or skipped care.
A simple way to decide
Compare the annual premium difference between two plans to the deductible difference. If switching to the high-deductible plan saves you $1,800/year in premium but raises your deductible exposure by $4,000, you'd need to go multiple years without hitting the deductible for the high-deductible plan to pay off — a bet that only makes sense if you genuinely have a low-usage year most years, and enough savings to cover the downside in a bad one.
Don't ignore the out-of-pocket maximum
The deductible is only the entry point to your cost-sharing, not the ceiling. Once you meet it, you typically still owe coinsurance until you hit your plan's out-of-pocket maximum — the actual worst-case number for the year. A plan with a low deductible but a high out-of-pocket max can still expose you to more risk than it looks like at first glance.
Rule of thumb
Choose the deductible you could pay from savings today without financial stress, not the one that produces the lowest monthly bill. The monthly premium is guaranteed; the deductible is a bet on your own health staying uneventful.