• Retiring early is the dream for many workers. Yet many people find themselves forced to call it quits because of health, career or family circumstances.
• "Many people may not even realize how severe the consequences can be," one expert said.

Many workers dream of an early retirement.

In reality, more than half of workers — 58% — retire earlier than they planned, usually due to unforeseen circumstances, according to new research from Transamerica Center for Retirement Studies in collaboration with Transamerica Institute.

The median age they call it quits is 62 — three years shy of the traditional retirement age of 65.

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Of those who retired early, most pointed to health-related reasons, with 46%; followed by employment issues, 43%; and family reasons, 20%.

Just 21% said they retired early because they are financially stable.

Earlier this year, the Employee Benefit Research Institute similarly found that half of retirees retired earlier than they expected, and most frequently for reasons they could not control.

Lost years 'absolutely critical' for retirement security

Unplanned early retirements can have severe financial implications for retirees, according to Catherine Collinson, CEO and president of Transamerica Institute and Transamerica Center for Retirement Studies.

"Many people may not even realize how severe the consequences can be and how absolutely critical those extra five or 10 years in the workforce can be in terms of achieving retirement security," Collinson said.

If those new retirees take Social Security benefits before their full retirement age — which is 66 to 67, depending on date of birth — they take permanently reduced benefits. The median age for claiming Social Security benefits is 64, according to EBRI. Retirees stand to get the biggest Social Security benefits if they wait until age 70.

Retirees who stop working at age 62 miss out financially in other ways.

They may lose five years of income, assuming they intended to retire at their full retirement age of 67, Collinson said.

They may also lose potential employer-sponsored retirement benefits and additional credits towards their Social Security work history.

They're also missing out on growth of their savings and investments, assuming they would have left those untapped if they kept working.

Plus, they have to pay for health insurance before the Medicare eligibility age of 65, which can be expensive, Collinson said.

Reset financial goals after an early retirement

People who are forced into early retirement may not have a lot of financial flexibility. But they should sit down and come up with a financial plan, which can help assess their risks of running out of money in the future, Collinson said.

If possible, newly retired individuals should try to give themselves time to pause and reset their financial goals, said Ted Jenkin, a certified financial planner and the CEO and founder of oXYGen Financial, a financial advisory and wealth management firm based in Atlanta.

When they do evaluate their finances, they should consider whether it would be advantageous to move, including to a place where taxes may be lower; carefully review the rules that come with COBRA or other health insurance plans; and take a look at any unused perks that may be available to them, such as credit card rewards, said Jenkin, who is also a member of the CNBC FA Council.

Still-employed pre-retirees should also take note and take steps now to try to extend their working years, Collinson said.

By keeping good health habits, making sure their job skills are up to date and relevant and continuing to build their professional networks, workers may avoid unforeseen early retirements, she said.