It may be the most pervasive question of retirement planning: When should I begin taking Social Security?

If you start collecting at the earliest opportunity -- age 62 -- you'll receive a permanently reduced benefit, but you could make out better overall if you live long enough to offset the reduction.

If you wait until your full retirement age, you can collect 100 percent of your benefit. You may lock into an even higher monthly check by delaying Social Security longer still.

Determining which option is right for you depends on a number of variables, including your life expectancy, financial picture and -- according to economists at the Center for Retirement Research -- gender and marital status.

Put it off
Generally, financial advisers say it's best to postpone Social Security benefits as long as possible, at least until your full retirement age as determined by the Social Security Administration (SSA).

Today, that ranges between ages 65 and 67. Those born in 1937 or earlier must be 65, while anyone born in 1938 or later sees full retirement age gradually climb to 67. 

"Social Security is like longevity insurance," says Brent Neiser, a certified financial planner and director of the National Endowment for Financial Education. "It's a stream of payments that will not stop throughout your life, so delaying your benefits to keep those payments as large as possible forms a helpful base to your retirement plan."

Early Social Security can cost you

• About 30 percent if you start collecting at 62 • About 25 percent if you start collecting at 63 • About 20 percent if you start collecting at 64 • About 13.3 percent if you start collecting at 65 • About 6.7 percent if you start collecting at 66

In fact, he notes, those who undersaved for retirement should use whatever means possible to postpone their Social Security benefits until after their retirement age to help boost future income.

If your full retirement age is 66, for example, you'll receive 108 percent of your monthly benefit by delaying Social Security until age 67.

If you wait until age 70, it jumps to 132 percent.

"You can use personal savings to help bridge the gap, but ideally you should plan to work a little longer (and delay Social Security)," says Neiser. "Not only does that save you money -- since you're not drawing money down from your retirement accounts -- but you're potentially adding more to it. Plus, you'll collect larger Social Security benefits (down the road.)"

Another benefit of working longer? Medicare.

Aging Americans become eligible for federal health insurance coverage at age 65.

"If you stop working at age 62 and lose health insurance, you have to get supplemental insurance to bridge the gap until you turn 65 and Medicare kicks in," says Neiser.

Paying for such insurance can quickly deplete your savings.