Sprinting through the final minutes of your run, the stressful seconds leading up to a big presentation, or watching Stranger Things alone in the dark: These are all times when you might feel like your heart rate won’t go down. But just going about your daily life shouldn’t lead to a racing heartbeat. Typically, your heart is part of a fine-tuned system that keeps the essential organ beating at a certain rhythm. So when the beats unexpectedly speed up, it’s understandable to feel concerned that something more serious might be happening to you.Your heart performs an incredible daily balancing act that’s crucial to keeping you alive and healthy. “The heart beats because of electricity,” Shephal Doshi, MD, director of cardiac electrophysiology at Providence Saint John’s Health Center in Santa Monica, California, tells SELF. No, not the type that keeps your lights on, although that would be interesting. Instead, these are electrical impulses from a group of cells in your heart’s right atrium (chamber) that act like your own internal pacemaker. These cells, known as your sinoatrial (SA) node, tell your heart when and how to beat in order to send oxygen-rich blood throughout your body.Sometimes, your body can signal your heart to beat faster, and the SA node responds. Other times, signals start coming from other parts of the heart, causing it to speed up. Whatever the reason, a racing heart rate, or heart palpitations, can make you feel anxious, among other unpleasant symptoms.A racing heart rate has many potential causes, very few of which signal something life-threatening like a heart attack or heart failure. What is important, however, is how your racing heart makes you feel and how often this switch in pace happens. Here are the most common reasons it feels like your heart rate won’t go down—and when you should consider seeing a doctor.What is a “healthy” resting heart rate? | Common causes of a fast heart rate | When to see a doctorFirst, how do experts typically define a “healthy” heart rate?A “normal” or healthy resting heart rate for most adults ranges from 60 to 100 beats per minute, according to the US National Library of Medicine. Between these rates, your heart can pump the oxygen-rich blood it needs to your vital organs. If you’re very physically active—say, you’re an avid runner—you may find your resting heart rate is much lower (sometimes as low as 40 beats per minute). This is because exercise, especially cardiovascular exercise, helps your heart work more efficiently, meaning it can squeeze out more blood at a slower rate, per the Mayo Clinic.A resting heart rate that’s consistently higher than 100 beats per minute or lower than 60 beats per minute (if you’re not an athlete) can signal an underlying health issue, according to the Mayo Clinic.Back to topWhat are the most common causes of a fast heart rate?Normally, your body’s systems run on autopilot, thanks to your autonomic nervous system, which regulates all the vital functions you don’t really need to think about. “This includes things like your heart rate, blood pressure, sweating, urination, and various gastrointestinal functions,” Brent Goodman, MD, a board-certified neurologist at the Mayo Clinic in Phoenix, tells SELF.Sometimes, though, certain lifestyle habits, situations, or even health conditions can cause your heart to start beating very rapidly or irregularly. Here are a few common culprits to keep on your radar.1. You’re feeling very stressed.Let’s be real: With everything going on in the world, there’s an extremely good chance you’re stressed right now. When you encounter something stressful, your body releases a surge of norepinephrine, also known as adrenaline, Camille Frazier-Mills, MD, a cardiologist at Duke Electrophysiology Clinic, tells SELF. Receptors in your heart respond to this trigger and can make your heart rate pick up.1If you can’t immediately solve whatever’s making you stressed (which is hard to do on a good day, let alone in the chaotic reality we live in), try deep breathing exercises to at least help you feel better in the moment. The Mayo Clinic suggests taking deep breaths through your nose so that you feel your stomach rise instead of your chest, and exhaling through your nose as well. Focus on your breath and the rise and fall of your abdomen throughout. (If you’re looking for a more detailed exercise to try, check out these relaxing deep breathing videos.)2. You’ve had a lot of caffeine.While most people can handle a certain level of caffeine just fine, overdoing it can make your heart rate speed up. “A bunch of patients come to see me with an elevated heart rate, then they tell me they drink multiple highly caffeinated beverages daily,” Dr. Mills-Frazier says. “They’re revving themselves up.” This is most likely to happen if you’ve had too much caffeine, but it could also happen in response to small amounts if you’re just sensitive to this stimulant.According to the US Food and Drug Administration (FDA), it’s technically safe for adults to have up to 400 milligrams of caffeine a day, or around the amount in four or five cups of coffee. If that sounds like a lot to you, it may be, since there is a wide range in how sensitive certain people are to the effects of caffeine and in how fast it gets broken down in the body. Certain medications and health conditions may also make you more sensitive to caffeine, including being pregnant. Try cutting back on caffeine gradually to see if it reduces your racing heart (just don’t try to cut it out cold turkey if you rather not deal with the unpleasant side effects of caffeine withdrawal). If that doesn’t help, get in touch with your doctor.3. You smoke.Smokers (tobacco, cannabis, marijuana, you name it) tend to have higher resting heart rates than those who don’t smoke, according to a 2015 study published in Circulation: Cardiovascular Genetics. Although doctors don’t exactly know why this happens, an increase in heart rate from smoking could come with other cardiovascular complications, including a heart attack.24. You have cold- or flu-like symptoms, like a fever.If your pounding heart is accompanied by typical cold- or flu-like symptoms, such as a fever, coughing, and sneezing, a viral illness might be the likely culprit. Battling any type of infection requires your body to work harder than usual, and that includes making your heart beat faster in order to fight for homeostasis (its usual stable condition) and kick the infection to the curb, Dr. Mills-Frazier says.