(MONEY Magazine) – With medical costs ballooning out of control, people who suddenly find themselves without health insurance are turning to short-term health policies. The 80 insurers offering these stopgap plans, which typically cover medical costs for as long as six months, are expected to collect around $150 million this year, up 10% from 1991. You too might be thinking about buying one if you recently lost your job, just started a new one where you aren't yet covered or have a child graduating from college who will no longer be carried on your health policy. But think twice before you buy: While short-term deals can be 40% to 50% cheaper than standard plans, they may not provide what you need. Specifically, short-term policies don't cover pre-existing conditions, so you'll collect only for new medical problems. Price is the policies' big selling point. For example, a 40-year-old Baltimore man with a 33-year-old wife and two children might pay between $165 and $220 a month for a short-term policy with a $250 deductible from two prominent providers, Golden Rule Insurance (317-297-4123) and Time Insurance (414-271-3011; not affiliated with Time Inc., MONEY's publisher). If the man had just quit his job at a company with more than 20 workers, a federal law known by its acronym COBRA would generally allow him to keep his employer's coverage for 18 months. But his COBRA rate would be about $380 a month, assuming his former company's policy was fairly comprehensive, says Roy Wilkinson, president of his own benefits consulting firm in Towson, Md. One reason: You're not much of a risk to an insurance company over such a short period. You may, however, be turned down if you are pregnant, have a major illness or were recently rejected by another insurer. Still, a short-term policy could make sense if you're healthy and want protection for a few months against the possibility of a catastrophic illness or accident. Just verify with your agent that the plan will pay medical bills for any conditions that develop while the policy is in effect. In most cases, you'll be covered for as long as three months after an injury, even if the policy has expired. You can apply for one more short-term policy from the company when the first one runs out; however, any medical problems that began after you bought the initial policy will be rejected as pre-existing conditions the second time around.