That steady beat you feel when you touch your fingers to your wrist, neck, or the inside of your elbow is good news—it means you're alive and kicking. And if you take a minute to figure out just how fast or slow it's thumping, you might learn something about how to keep your health in check.
Determining your heart rate is easy; just take your pulse and count the beats for a full minute. But that info is most useful if you track it over time and tell your doctor about any substantial shifts, says Pam R. Taub, MD, a board-certified cardiologist and associate professor of medicine at the University of California, San Diego.
"What's even more important than a single heart rate is the trend," she says.
Taub says that the ideal resting heart rate for most people is between 60 and 85 beats per minute (bpm), though some doctors say up to 100 bpm is OK. If yours is too low (bradycardia) or too high (tachycardia), it could be your body's way of sending out an S.O.S. to tell you something's not right.
So what could be troubling your ticker? Here are a few reasons that might explain why your heart rate is out of whack.
1. You're stressed
Stress can make your heart pound and blood pressure rise, which throws your body into the "fight or flight" mode. (Important note: Heart rate and blood pressure aren't the same thing, and they don't always rise or fall in tandem.) Chronic stress keeps you—and your heart—in a state of high alert, which increases your chances of having a heart attack or stroke, says Taub.
More From Prevention: 5 Signs You're Not Getting Enough Vitamin D
2. You have diabetes or are on your way to getting it
Doctors aren't clear on whether a high heart rate causes diabetes or if diabetes causes a high heart rate, but recent studies show that the two are definitely related.
Often, says Taub, people who develop diabetes are less active and more likely to have coronary disease and high blood pressure, all of which strain the heart. And when your heart's not happy, it can lead to other problems down the road.
"There are a lot of studies that link higher heart rate, especially in patients with diabetes, to more adverse outcomes," says Taub.
3. There's a short in your heart's electrical system
Your heart has its own electrical (conduction) system—a network of signals that help it beat correctly—and a slow heart rate might indicate an abnormality, says Taub. People who have an electrical problem may feel dizzy or lightheaded. Your doctor should be able to detect and pinpoint the malfunction with a simple EKG.
More From Prevention: 12 Foods That Lower Cholesterol Naturally
4. You're not getting enough exercise
You know the phrase "use it or lose it"? It applies to your heart. It's a muscle, and it needs exercise to perform at its peak.
"Inactivity and obesity often contribute to an elevated resting heart rate," says Taub.
Why? Because when you're out of shape, your heart has to work harder to get your blood where it needs to go. Plus, the bigger you are, the more blood you need. More blood to pump equals more heartbeats per minute.
The flip side is that getting a lot of exercise can lower your resting heart rate. Serious athletes typically have resting heart rates that are lower than 60 bpm.
More From Prevention: How To Start Walking When You Have 50+ Pounds To Lose
5. Drugs (including prescription ones) are messing with your numbers
Certain medications can reset your heart rate readings and give you a new normal.
"Beta blockers and calcium channel blockers are the main ones that can lower a heart rate," says Taub.
Both relax your heart, which can slow it down. That's not necessarily dangerous, but check with your doctor if you have any concerns.
Caffeine, on the other hand, can ramp up a heartbeat in a hurry. It's often found in headache medications, and it lurks in certain food and drinks, like tea and chocolate.
"Some people are extremely sensitive to caffeine, so they drink a coffee or an energy drink, and they immediately get elevations of their heart rate," says Taub.
Cutting back should help. (Here are easy ways to cut back on caffeine.)
6. You're dehydrated or too hydrated
Minerals in your body with an electric charge are called electrolytes. If you drink too much water or not enough, it can throw off the ratio of electrolytes to water in your system, which messes with your body chemistry.
"If your potassium, calcium, or magnesium levels are very low, that can induce arrhythmias [abnormal rhythms], which can manifest as a higher heart rate," says Taub.
7. Your thyroid is under- or over-active
Your thyroid—the butterfly-shaped organ in your neck—produces hormones that help your body function correctly. If it's not making enough, it means you have hypothyroidism, which could cause your heart rate to be low, says Taub.
On the other hand, if it's overperforming and pumping out extra hormones, you have hyperthyroidism, which can raise your heart rate. Your doctor can test your thyroid function with a blood test.