Finding the right health insurance at the lowest cost is important to almost every federal worker. But for the 100,000 government retirees in this area, finding the right plan can be a critical decision.

Older people usually have less money to spend on insurance and more need for health insurance. The typical federal retiree in the Washington area gets a pension of just over $12,000 a year. Many widows of government retirees exist on much less.

Everybody covered by the federal health program -- and that includes half the men, women and children living here -- must decide on their 1985 health plan by Dec. 7.

According to estimates, the typical person between ages 19 and 64 will have $1,500 in medical, hospital and drug expenses next year. The Washington Consumers Checkbook Guide to Federal Health Insurance Plans says that the average expense next year for people 65 and older will be $3,000, exclusive of any nursing home costs.

Federal workers with Medicare coverage are in relatively good shape. They usually can get overall protection with a relatively low-cost health plan, because Medicare will pay most of their bills.

The Checkbook guide suggests that those retirees consider health maintenance organizations because the HMOs offer good coverage at lower cost than many standard health plans.

U.S. retirees -- or their spouses -- without Medicare usually need better health insurance protection.

Here are two lists of plans that Checkbook advises retirees to consider during the open season. The first list is of plans that provide good coverage at the lowest cost for persons with Medicare. The second list is plans that Checkbook recommends for persons without Medicare coverage:

*If you have Medicare, Checkbook suggests you get the brochures (from the plans themselves) for these plans: National plans recommended include Blue Cross-Blue Shield standard option, Aetna standard option, National Alliance standard option, GEHA, Postmasters low option. If you are eligible, it also suggests you consider the National Association of Postmasters Plan, Special Agents Mutual Benefit Plan, Government Employees Benefits Association plan low option and the Foreign Service plan.

HMOs that you should consider include Kaiser-Georgetown, MD-IPA, Group Health low option, and George Washington University health plan.

*If you do not have Medicare, Checkbook recommends that you consider these plans. The plans are rated for coverage they provide at the lowest total cost: MD-IPA, Columbia Health Plan, Group Health, Kaiser-Georgetown, George Washington, HealthPlus high option, CHOICE, SAMBA, Blue Cross standard, Foreign Service, GEHA, HealthPlus standard option, National Alliance high option, NAPUS, Aetna standard option, Rural Letter Carriers, GEBA high option, Mail Handlers low option, National Association of Government Employees standard option, Postal Supervisors, Alliance standard option, National Treasury Employees Union standard option, NAGE high option, Mail Handlers low option, American Federation of Government Employees high option preferred plan, National Federation of Federal Employees, NTEU high option, American Postal Workers Union plan, Postmasters low option, AFGE high option, AFGE standard, Blue Cross high option and Postmaster high option.

All but one of the plans are run locally and are listed in the telephone directory. They will supply brochures -- which you should study carefully -- upon request. Brochures from the GEHA plan (in Kansas City) can be had by calling (800) 821-5199.

Retirees who want information may call 632-6712 or write P.O. Box 809, Washington 20044.