Stock market losses early in retirement can significantly increase your chances of running short of money. Financial planners say the following actions can help make your money last.

Make sure you are properly diversified. When the stock market is booming, investors can be tempted to "let it ride" rather than regularly rebalancing back to a target mix of stocks, bonds and cash. Not rebalancing, though, means those investors probably have way too much of their portfolios in stocks when a downturn hits.

Many financial planners recommend retirees keep a few years' worth of withdrawals in safer investments to mitigate the urge to sell when stocks fall.

Certified financial planner Lawrence Heller uses the "bucket" strategy to avoid selling in down markets. Heller typically has clients keep one to three years' worth of expenses in cash, plus seven to nine years' worth in bonds, giving them 10 years before they would have to sell any stocks.

"That should be enough time to ride out a correction," Heller says.

Near-retirees who use target-date funds or robo-advisers to invest for retirement don't have to worry about regular rebalancing — that's done automatically. But they may want to consider switching to a more conservative mix if stocks make up over half of their portfolios.

Start smaller, or be willing to cut back. Historically, retirees could minimize the risk of running out of money by withdrawing 4% of their portfolios in the first year of retirement and increasing the withdrawal amount by the inflation rate each year after that. This approach, known as the "4% rule," might not work in extended periods of low returns. One alternative is to start withdrawals at about 3%.

Another approach is to forgo inflation adjustments in bad years. Derek Tharp, a researcher with financial planning site Kitces.com, found that retirees could start at an initial 4.5% withdrawal rate if they were willing to trim their spending by 3%.

Pay off debt, maximize Social Security. Melissa Sotudeh, a certified financial planner in Rockville, Md., recommends paying off debt before retirement and maximizing Social Security checks by delaying benefits, which can increase by about 5% to 8% for each year people put off starting Social Security after age 62.

If needed, arrange more guaranteed income. Ideally, retirees would have enough guaranteed income from Social Security and pensions to cover all of their basic expenses, such as housing, food, utilities, transportation, taxes and insurance, said Wade Pfau, of the American College of Financial Services. If they don't, they may be able to create more guaranteed income using fixed annuities or reverse mortgages, says Pfau.

Covering expenses with guaranteed income actually can free retirees to take more risk with their investment portfolios, which over time can give them better returns and more money to spend or leave to their kids, Pfau said.

"They'll be able to invest more aggressively and still sleep at night because they don't need that money to fund their day-to-day retirement expenses," he said.

Consult an expert. Most people don't consult financial planners to make sure their investment, withdrawal and Social Security claiming strategies make sense. Getting that second opinion, preferably from a fiduciary adviser committed to your best interests, is critical.

E-mail: lweston@nerdwallet.com. Twitter: @lizweston.