Even if you do a good job of saving for retirement, there are some expenses that could take a massive chunk out of your retirement savings that you aren't anticipating. Specifically, healthcare costs, investment expenses, and college expenses could consume more of your hard-earned retirement nest egg than you think.

Healthcare: The six-figure retirement-savings destroyer

The average couple who reaches 65 years old in 2018 will need about $280,000 saved to cover healthcare expenses throughout their retirement, according to Fidelity. And it's important to mention that Fidelity's estimate doesn't include two potentially large additional expenses -- taxes and long-term care.

Man holding wallet open with money flying away.

Image source: Getty Images.

First, the $280,000 figure is an after-tax­ amount. If your retirement savings is in tax-deferred accounts like a traditional IRA or a non-Roth 401(k), your withdrawals will be treated as taxable income. As one example, if you're in the 22% tax bracket, in order to get $280,000 to cover healthcare costs throughout your retirement, you'll actually have to withdraw about $359,000 because of federal income taxes, and even more if you have to pay state taxes.

You can get around this tax hit by keeping some of your retirement savings in a Roth IRA or by making Roth 401(k) contributions if your employer offers them. Or better yet, if you're eligible to participate in a health savings account (HSA), it can help you save money on taxes both immediately and on healthcare costs in retirement.

Second, long-term care can be extremely expensive and isn't covered by Medicare. If you or your spouse end up needing care in a nursing home, it can easily cost more than $100,000 annually in many parts of the U.S. Because of this, you may want to consider long-term care insurance as you approach retirement age.

Investment fees

I recently wrote an article about how paying excessive investment fees could literally cost you a six-figure sum before you retire. And I'm not talking about massive hedge fund fees or large variable annuity commissions -- I mean the difference between mutual funds with seemingly low expenses.

One thing investors should be aware of is that actively managed mutual funds tend to come with significantly higher fees than passive index funds, yet the majority fail to beat their underlying benchmarks. For example, in 2016, two-thirds of actively managed mutual funds underperformed. So don't think that by paying higher fees you can expect better returns. More often than not, the exact opposite is true.

Here's a simplified example of how this can affect your retirement savings. Let's say that you have two investment choices -- a passive index fund with a 0.05% expense ratio and an actively managed fund with a 0.5% expense ratio (which is actually cheap for an actively managed mutual fund). We'll say that both funds achieve the same long-term investment performance of 9% per year.

In this case, a $100,000 sum invested in the index fund for 30 years would grow to $1.31 million, while the same amount invested in the actively managed fund would grow to $1.16 million -- a difference of approximately $150,000.

Your children

For many people, children are a drain on retirement savings. For starters, kids are expensive -- plain and simple. For what I pay in day care costs for my two young children, I could literally afford to buy a new Porsche 911 (or more responsibly, to boost my retirement savings). So it's fair to say that many parents don't save as much for retirement as they'd like to just because of the day-to-day expenses associated with raising children.

Furthermore, many parents say that they may use their retirement savings to help pay for college. According to a recent Sallie Mae study, 10% of parents say that they plan to use their retirement savings toward college, while another 21% say that they could use them if it's necessary.

So what can you do?

Here's a quick rundown of steps you can take to plan for healthcare costs in retirement, avoid investment fees draining your savings, and better prepare for college costs:

  • Save money specifically to cover healthcare costs in retirement. A health savings account is an ideal place to do this -- if you qualify for one.
  • Consider buying long-term care insurance as you get close to retirement age.
  • Always compare the costs of investments. This includes the funds offered by your 401(k), as well as the mutual funds and ETFs you buy in brokerage accounts.
  • Make use of college-specific savings vehicles, like 529 savings plans, so you don't have to dip into your retirement savings to pay for college.