Workers who hope to avoid furloughs and collect a modest 3.5 percent January pay raise get a break this year in their health insurance. After several years of big premium jumps, rates for 1991 are going up an average of just 5.7 percent. That looks good compared with the 13 percent jump recorded last January.

But workers and retirees need to shop for the best bargains during the open season that starts in mid-November. Some plans will have a modest increase; a couple will hold the line; a few will cut premiums.

Many workers and retirees would be smart to switch from high-option to standard-option coverage. Benefits often are similar. But many high options are costly because they are popular with so-called heavy users.

People in the American Federation of Government Employees plan; National Federation of Federal Employees plan; National Association of Government Employees plan; Postal Supervisors; and the Government Employees Benefit Association will have to find new insurance. Those plans -- with about 45,000 subscribers -- won't be offered next year.

Under the premium-sharing system, the government will pay about 60 percent of the average premium. But averages vary. Depending on the plan and option, the government will pay as little as $45 or as much as $150 of the total biweekly premium.

But the bottom line is what you pay and what you get for it.Here are the 1991 premiums for local indemnity plans. Later, we'll have rates for health maintenance organizations. Amounts shown are for federal workers who are paid biweekly. Retirees pay the same rates, but on a monthly basis:

Blue Cross-Blue Shield: The high-option, self-only plan will go up $9.12 every pay period for individuals and $19.02 for family coverage. Premiums for the standard option will remain at $16.92 and $35.55.

Alliance: High-option self-only up $70.45 per pay period, family up $21.68. Standard self up $1.64 and family up $3.94.

American Postal Workers Union: Self-only up 71 cents, family up $2.62.

GEHA: Self-only up 98 cents, family up $3.43.

Mail handlers: High self-only up 57 cents, family up $1.25; standard self-only up 68 cents, family up $1.47.

NALC plan: Self-only up $3.68 and family up $6.33.

NTEU plan: Self-only down $3.10, family down $12.69.

Beneficial Association of Capitol Employees: Self-only down 72 cents, family down $8.28.

Foreign Service plan: Self-only down $3.74, family down $13.26.

NAPUS Benefit plan: Self-only down $3.19, family down $6.98.

Postmasters Benefit: High self-only up $19.69, family up $42.50; standard self-only up $3.22, family up $18.08.

Rural Carriers: Self-only and family plans both are down $1.06.

SAMBA Health plan: Self-only down $4.48, family down $17.09.

Secret Service plan: Self-only up $2.83 and family up $7.07.