You work out regularly. You don’t smoke. Your diet is (at least relatively) in check. You don’t need to worry about heart health at all, right? We don’t want to get all alarmist on you, but you actually should start thinking about it, like yesterday.

“Every day in my office I see patients who have healthy lifestyles, who are doing what we’d think of as the right thing—they’re exercising frequently and watching their weight, they’ve stopped smoking—but yet, they still have a risk of heart disease,” says Lawrence Phillips, M.D., Director of Nuclear Cardiology at NYU Langone Medical Center and member of the American Heart Association’s Board of Directors in New York City.

That’s because there are certain risk factors for heart problems that are silent. And, believe it or not, heart disease affects 12% of men under 40, and 41% of men under 60, per the AHA. In fact, it’s the No.1 killer in the U.S.—striking one person every 43 seconds.

You can find out what your risk is for heart problems with this risk assessment calculator from the American Heart Association. But regardless, consider these five things now. Yes, while you’re young and healthy.

1. Get your cholesterol and blood pressure checked

“What everyone needs to do right off the bat is have their cholesterol screened,” says Phillips. “For young, otherwise healthy people, we want to make sure that there’s no genetic abnormality that’s causing the cholesterol to be elevated.” Phillips says that everyone over 18 should have a cholesterol screening performed every five years. Talk to your regular doctor about the test. "If we catch it, and it’s very elevated early on, then we’re able to treat it and lower your disease risk," says Phillips.

“One of the main risk factors for heart attacks, stroke, and other heart issues is high blood pressure,” says Phillips. The scary thing is that you can have high blood pressure and exhibit zero symptoms for up to 15 years. The only way to know it’s high—and do something about it—is to get it checked. If left unchecked for several years, elevated blood pressure can increase your risk for heart attack and stroke (so take the two minutes to get screened).

2. If you’re an athlete, be careful

You may think this means you have a free pass to care even less about your heart, but the fact is that if you’re an Iron Man or marathoner, you need to pay extra attention to it. “Anyone who is participating in these high-intensity activities should have full pre-training examinations with a physician, which in some situations will include an EKG,” says Phillips. The reason? Although great for you, these things put extra stress on your heart (some people even say extreme endurance exercise is bad for you.) So, you don't have to forgo the race, just get screened prior to signing up.

3. Get into cardio

That said, everyone needs some cardio. It’s awesome if you’re already lifting weights regularly, but research shows aerobic exercise is key for heart health. “It’s important to not just do weight training, but to get your heart rate up, too,” says Phillips. The AHA recommends getting in 30 minutes of moderately intense cardio five days a week or 25 minutes of vigorous cardio 3 days a week.

4. Think about your diet

Restricting salt intake is important for everybody, whether they’re athletes or not, says Phillips. That's because it can increase blood pressure. Also key for heart health: Avoid saturated fats, which can raise bad cholesterol

5. Spot the signs

If you experience a sudden change in energy levels, talk to your doctor. "Somebody who’s able to exercise at certain intensities, or is able to run a certain amount on the treadmill and then all of a sudden notices that they’re not able to exercise at that activity level; that’s a red flag that you need an evaluation," says Phillips. Other signs to be on the lookout for: dizziness, shortness of breath, a rapid change in the heart beat, and chest pain. "Don’t work through the symptoms," says Phillips. Stop what you're doing and get it checked out.