Many people associate age 65 with retirement, and there's a reason for that: Medicare eligibility begins at 65. You may be thinking that once you're eligible for those health benefits, you'll sign up for Social Security as well. But here's a good reason to reconsider that plan.

Can you afford a hit to your benefits?

Many people don't enter retirement with a comfortable level of savings and, as such, rely heavily on Social Security to make ends meet. If you're behind savings-wise, filing for Social Security at age 65 could leave you with a much lower monthly benefit than you want.

Older person at laptop

Image source: Getty Images.

You're entitled to your full monthly benefit based on your earnings history once you reach full retirement age, or FRA. FRA is a function of the year you were born, as follows:

Year of Birth

Full Retirement Age

1943-1954

66

1955

66 and 2 months

1956

66 and 4 months

1957

66 and 6 months

1958

66 and 8 months

1959

66 and 10 months

1960 or later

67

Data source: Social Security Administration.

As you can see, age 65 does not appear on this table because it's not FRA for anyone who might be contemplating filing for benefits. As such, if you decide to claim Social Security at 65, your monthly benefit will be reduced on a permanent basis.

The extent of that hit depends on what your FRA is. If it's age 67, filing at 65 will slash your monthly benefit by 13.34%. If it's age 66 and two months, you'll slash your benefit by a little less than 8%. Either way, though, that's money you'll need to live without as you navigate retirement, so filing at 65 is a decision you may ultimately regret.

When should you claim Social Security?

If you expect to rely heavily on Social Security as a senior, then it pays to push yourself to wait until at least FRA to sign up. A better bet, however, may be to delay your benefits past FRA. For each year you do, up until you turn 70, your benefits increase by 8%. This means that if you're looking at an FRA of 67, filing at 70 will give you 24% more monthly income to look forward to for life.

How to sign up for Medicare without Social Security

If you're worried that holding off on Social Security past the age of 65 will be problematic from a Medicare standpoint, fear not. When you create an account on the Social Security Administration's website and go to sign up for Medicare, you'll be asked if you want to enroll for health benefits only, or for Medicare plus Social Security. Simply indicate that you're only looking for Medicare coverage, and your Social Security benefits will continue to grow. The only thing you need to know in that scenario is that you'll have to pay your Medicare Part B premiums yourself. Seniors on Social Security have those premiums deducted from their monthly benefits.

Remember, there's no right or wrong age to file for Social Security. It could be the case that claiming benefits at 65 is a smart decision for you. But it's important to understand the repercussions of filing at that age, and to make sure you're making that choice for the right reasons.