The main dangers with DIY home improvement or renovation projects are that you could hurt yourself and potentially incur medical expenses, or cause damage to your home, which might mean bringing in a professional to fix or finish it.

That could end up costing more money than if you had hired the pro in the first place, as a general contractor can charge up to 25% of the completed project’s cost for labor. That’s potentially hundreds or thousands of dollars.

For those who plan to push ahead, injuries are a real concern. Even if you’re doing something mundane that may require you to climb a ladder, mow the lawn, or swing a hammer, the chances that you’ll get hurt are higher than you might think.

A new survey from insurance and financial product provider Guardian says that 20% of Americans who take on a DIY home improvement project experience injuries serious enough to require medical attention. And 5% of respondents say they were injured so severely that they required long-term care, or multiple follow-ups with doctors.

The most dangerous projects, per Guardian’s analysis, involve carpentry, fixture installation, and landscaping.

“The data shows that 77% of Americans take on DIY projects,” says Mike Estep, vice president of group products and worksite leader for Guardian. But in the event that you’re injured on a DIY project, you may be reluctant to use health insurance to cover the costs, often because their deductible is higher than the cost of care.

The average emergency room visit costs more than $2,000, according to an analysis from UnitedHealth Group, for example. Meanwhile, for people with high-deductible insurance plans, the average deductible is nearly $2,500.

So even if your health insurance policy does cover the expenses of receiving care for an injury, the costs of using it can be prohibitive.