Many retirees regret taking their Social Security benefits early, according to a Nationwide Financial Retirement Institute survey released Wednesday.

Thirty-eight percent of retirees wish they had waited to start taking Social Security, says the survey. Social Security benefits grow the longer the beneficiary waits to start collecting.

“Social Security can represent up to 40 percent of the total income the average worker receives throughout retirement and when and how to file are some of the most important financial decisions they make in their lifetimes,” says David Giertz, president of distribution and sales for Nationwide Financial. “With more than 2,700 rules in the Social Security handbook, it’s easy to see why many aren’t aware of all of the benefits and options available to them.”

Health-care costs are among the issues facing retirees but having a financial advisor helps, according to the survey. One third of retirees without an advisor say health-care costs are preventing them from doing what they want in retirement, compared to 13 percent of retirees with an advisor.

“The key theme throughout our survey is how crucial it is that Americans work with a financial advisor,” says Giertz. “Optimizing Social Security benefits is an important part of a holistic retirement plan.”

Retirees not working with a financial advisor are more than twice as likely than those who do to say their Social Security payment was less or much less than expected (33 percent versus 12 percent), the survey found.

In addition, retirees working with a financial advisor are more likely (82 percent) than those not working with a financial advisor (62 percent) to say they are able to do the things they want in retirement.

The survey included 903 respondents age 50 and older who were retired or plan to retire in the next 10 years.