Government workers, their families and retirees would have their health insurance benefits guaranteed for a two-year period under a plan being considered by the Office of Personnel Management.

OPM runs the giant federal health program that covers 9.2 million people and helps pay the medical bills of nearly a million Washington area residents.

Premiums this year jumped an average 30 percent. But premium-payers were denied a chance to go on their annual insurance shopping trip, even though most of the plans that raised rates also reduced coverage.

OPM soon will announce an open enrollment period in May, for workers and retirees who want to switch health insurance coverage (with changes effective in July) for the remainder of this year.

OPM is also planning to have another open season, in November, so people can pick their 1983 health plans. Premiums and benefits for the 1983 year will be determined later this summer.

The 24-month benefit protection plan, if approved, would start for the 1983 insurance year. Premiums could be adjusted every 12 months. And employes and retirees would have a chance to switch to another plan every 12 months. But benefits would not change for two years.

The two-year benefit freeze would also bar the government during that time from forcing companies to make benefit cutbacks, which it did last year for the 1982 insurance year.

Employes who wished to make changes because of premium increases could do so. But there would be no reason to switch because of benefits, which would remain the same for the contract period. It would save OPM millions of dollars, since it would not have to print annual brochures outlining benefit changes in the 120 plans in the program. Every other year OPM would only print rate change cards.