Nearly a third of the government's retired and active work force switched health insurance plans between May and December last year, burying federal and private insurance offices under an avalanche of very important paperwork.

The shift from one plan to another (some employes changed twice) was prompted by mass confusion over benefit levels in early 1982 and an eye-popping 55 percent jump in premiums during a 12-month period.

It is estimated that more than a million employe and retiree policy-holders, anxious to get the best coverage at the lowest cost, moved themselves (and their families) to a new health plan in January.

The Federal Employe Health Benefits program (FEHB) consists of more than 120 plans covering 9.2 million members of the federal family, from the president to government cowboys and computer analysts, ex-senators and the children of civilian astronauts.

FEHB plans range from nationwide giants such as Blue Cross-Blue Shield, which is open to everyone, down to specialized group plans that are limited to folks at the super-secret National Security Agency and to CIA agents who, contrary to popular fiction, are rather good health risks.

In metro Washington where the industry is government, every other man, woman and child depends on the FEHB to watch over their mental, dental and physical health care needs.

Because of the record number of switches last year--when there were two health insurance "open seasons"--many people who changed from one plan to another still have not received ID cards, claims forms or even acknowledgement from their new health plans that they are aboard.

Based on preliminary data from health plans, the biggest loser because of the switching is Blue Cross-Blue Shield's high option plan, which has one of the highest premiums. The BC-BS "standard" option was a big gainer, however, as was the Kansas City-based GEHA plan, which has more than doubled its membership.

Because of the influx of new subscribers, GEHA is one of the carriers that is backlogged in sending out ID cards to new subscribers.

If you are one of those people who have not received an ID card from your new health insurance plan, you can use a copy of the form you filled out to switch plans (Health Benefits Registration Form 2809) to prove to a doctor or hospital that you are covered.

Meantime, insurance plan officials say they hope to have all of the changes acknowledged within the next couple of weeks.

Because of the backlog, payroll deductions to cover insurance premiums for some employes and retirees are being made based on the premiums charged by their old plans. Office of Personnel Management officials say that adjustments will be made as soon as possible.