U.S. workers eager for better, or cheaper, health insurance coverage will get the word soon when they can switch, what it might cost them to do so, and what benefits they could lose in the process. The Office of Personnel Management is now considering whether to hold an open season May 3 through 28 for the federal health insurance program, which helps pay doctor and hospital bills of nearly a million people here. Unless Congress steps in, it is up to OPM alone to decide:

* Will there be a May open season?

* Will there be an open season in November so people can decide 1983 insurance needs?

* Should people who switch plans in mid-year be forced to pay transfer fees?

* Should subscribers who move into a new health plan be required to meet its deductible, even if they have already satisfied deductible requirements in their current plan?

* Will certain preexisting medical conditions, like pregnancy or expensive mental health treatment, be excluded from coverage if the individual picks a new health plan?

If there is a May open season (with coverage beginning in July) without conditions, a lot of people may switch. Health premiums rose an average of 30 percent this year. A lot of people are itching to get out of more costly plans (which have the most comprehensive benefits) and slip into something a little more comfortable, even if it covers less.

If, however, OPM imposes conditions on those who switch health plans, like transfer fees, exclusion of preexisting medical conditions or new deductibles, a lot of people who want to make the change for financial reasons may decide they can't afford to switch so late in the year.

Benefits brochures for most of the 126 health plans are available at agencies. Employes can study them to see what they might do if there is a May open season. But the majority won't be able to decide whether to switch or stay until they learn what strings are attached to a new open season.