Do you have a plan for how much you money you'll need in retirement? Whether you already have a savings goal or need to create one, it's essential you really think about the kinds of expenses you're likely to face.

Far too many people think their spending will go down compared to when they worked. Sadly this isn't necessarily true. In fact, there are some big expenses you may be hit with in retirement that could cause you to spend far more than you expect. If you aren't planning for these costs, you could find yourself in dire financial straits.

Here are three big expenses -- that you're probably forgetting -- that should be factored into savings goals or calculations used to determine if your savings is enough to sustain you after you leave the workforce.

Binder labeled retirement savings plan with a calculator and glasses on top of it.

Image source: Getty Images.

1. Helping out your family

If you have kids, chances are good they'll rely upon you to provide them with a little financial help -- even as you get older.

In fact, one study from TDAmeritrade found millennial parents with children of their own relied upon mom and dad in a big way, receiving an average of $11,011 in financial support or unpaid labor from their parents over the course of a year.

Some retirees not only have the younger generation counting on them, but they're also still providing care and financial support to aging parents. As many as one out of every two people who live past 85 years old need nursing home care, and some retirees have to help their parents cover the costs of medical issues at the end of their lives.

While you can say no to your loved ones, it's hard to turn your back on family -- even if you're compromising your own future financial security.

Unless you're 100% confident you won't need to provide financial help, budget a few thousand dollars in annual extra spending when figuring out your projected retirement needs so your generosity won't leave you broke. If you don't spend it, you can enjoy it later or leave it to your loved ones after you're gone.

2. Healthcare costs

When you've retired, don't count on Medicare to cover all your healthcare expenses. Senior couples are expected to spend between $280,000 and $370,000 on healthcare costs out of pocket, even with Medicare coverage. 

Medicare is so expensive because it doesn't cover many kinds of care, and there are coinsurance expenditures and premiums to pay. Supplemental insurance -- Medigap policies -- require you to pay additional premiums. And even with a supplemental plan, out-of-pocket expenditures on drugs and medical service can still total thousands of dollars each year.

To avoid having your retirement derailed by unexpected medical expenses, invest in a health savings account (HSA) if you're eligible to do so because you have a high-deductible health plan. Put money into the HSA pre-tax and allow it to grow tax free. You'll also get tax-free withdrawals, as long as you're using the funds to cover medical expenses. This makes HSAs one of the most valuable accounts for saving for your senior years. 

If you can't invest in an HSA, bump up your retirement savings goals to account for the fact you'll need to spend around $6,600 per year on care, which was the mean spending on healthcare for people over 65 years old in 2017. Even if you don't spend it every year, it will be there for you when a big medical emergency strikes.

3. Long-term care costs

Early in your retirement, your concern about nursing home costs might relate to your parents -- but later in life, it may be your move to a nursing home you must finance.

Whether you get long-term care at home or move to an institutional setting, expect to pay a small fortune. In fact, according to the 2018 Genworth Cost of Care Survey, a home health aide costs an average of $50,336 annually; a semi-private room in a nursing home would run you $89,297; and a private room comes at a cost of $100,375 per year. 

Medicare won't cover long-term care at home or in a nursing home unless you meet very specific requirements and need skilled nursing care provided by staff with medical training. Most people don't need this, but instead require custodial care -- basic help with daily living tasks such as eating or dressing -- which isn't covered by Medicare.

Buying long-term care insurance is one way to plan for care costs, but policy premiums can become prohibitively expensive as you age and many policies come with coverage limitations that render them useless. Another option is to consider how much nursing home care would likely cost per year and make sure your retirement nest egg is big enough that income from investments could be enough to pay.

You need a plan to cover these big expenses

Whether you help your parents or kids, get hit by big medical bills, or end up in a nursing home, chances are good you'll experience at least some big unexpected expenses in retirement. Planning in advance to make sure you have needed funds is imperative, so don't forget to factor all of the essentials in when setting your retirement goals.