The obvious solution is to make sure women save enough money to cover the longer spread and to work as long as possible, but that is not what is happening out there in the real world.

When it comes to early retirement, which most define as before 65, a study from Fidelity released Thursday found that the top reason women leave the workforce early is because of a health concern. This health matter typically relates to a spouse, but also sometimes to elderly parents or even grandchildren.

One of Abe Ringer's financial planning clients presents a common scenario. This woman stopped working when she was 63 to care for her husband until he died of lung cancer. Rather than return to the workforce, she shifted to caring for her grandchildren so her daughter could work.

She will probably have enough funds for her later years, but Ringer, who is based in Boston, has other clients he worries about.

"With any type of financial planning, we're operating with a certain degree of uncertainty," he said.

Healthcare costs are one of the most unpredictable factors of retirement. The Fidelity study estimated than women over 65 will need $147,000 for healthcare in retirement, while men will need just $133,000. That number does not include long-term care.

Those who retire before Medicare kicks in at 65 have additional costs because they have to pay for coverage - either cost-sharing with an ex-employer or on the open market, said Katie Taylor, vice president of thought leadership at Fidelity.

To avoid running out of money, there are several areas where women can make strategic decisions:

KEEP WORKING

One of the major reasons women save less than men is that they spend 44 percent of their adult lives out of the workforce, compared to just 28 percent for men, according to a study from Merrill Lynch on Women and Financial Wellness released Thursday.

The result: A potential cumulative wage gap of over $1 million.

To combat this, working women need think about the long-term impact of stopping work.

"Retirement is no longer a switch that you turn on and off," said Maddy Dychtwald, co-founder of Age Wave, which conducted the study with Merrill Lynch

At the very least, try to keep one toe in the workforce.

"Part-time work is so impactful," said Ringer.

He has one client who stopped working in her early 60s, because her husband was older and was retiring. Now he is ill, and Ringer is worried her funds will run out after he dies, so he is counseling her to pick up consulting projects.

"I am awestruck at the women who have started over," said Catherine Collinson, president of the Transamerica Center for Retirement Studies. "They go out and look for part-time work, and then demonstrate how good they are. It’s really inspiring."

DO A COST-BENEFIT ANALYSIS

The Merrill Lynch study noted that two-thirds of care provided to older adults is done by women.

Before one person in a family stops working to become a caretaker, Stuart Ritter, senior financial planner at T. Rowe Price, suggested polling everyone involved (siblings, adult children, etc.) to see if the care can be divided without anyone having to stop work. The group can pool resources to pay for a caregiver instead, too.

Ritter said family members can also all chip in for a long-term care policy for the ailing relative, and get the care covered by insurance.

DOWNSIZE

When it comes to making hard decisions when the money is gone, Ringer suggests anything else but starting pensions and Social Security early.

"Hold off, even if it means drawing down other accounts first," he said.

With Social Security, claiming at any age prior to 70 chips away at benefits. Many private pensions also have age triggers.

Homeowners who are running short of money can sell. Or they can take a reverse mortgage, which allows a homeowner to cash out of the house while still living there. These contracts are more expensive than they used to be, but Ringer said they can be useful if you turn the payments into an annuity so you have steady income.