A resting heart rate below 60 or above 100 beats per minute (bpm) is generally considered outside the normal range for adults. But “unhealthy” depends on context: a well-trained athlete might sit comfortably at 45 bpm, while someone with an anxiety disorder might regularly hit 105 bpm without any heart damage. The numbers matter most when they come with symptoms or persist without explanation.
Normal Ranges by Age
Heart rate norms shift dramatically from birth through adulthood. A newborn’s resting heart rate can be as high as 205 bpm, which would be a medical emergency in an adult. Here’s what’s typical at rest:
- Newborn (birth to 4 weeks): 100 to 205 bpm
- Infant (4 weeks to 1 year): 100 to 180 bpm
- Toddler (1 to 3 years): 98 to 140 bpm
- Preschool (3 to 5 years): 80 to 120 bpm
- School age (5 to 12 years): 75 to 118 bpm
- Adolescent (13 to 17 years): 60 to 100 bpm
- Adult (18+): 60 to 100 bpm
These ranges apply when you’re awake and sitting still. Sleep can push your rate lower, and activity will push it higher. For adults, the 60 to 100 window is a useful guide, but where you land within it tells you something about your cardiovascular fitness and long-term risk.
Too Fast: What a High Resting Rate Means
A resting heart rate above 100 bpm is called tachycardia. It can be temporary and harmless, triggered by caffeine, stress, dehydration, or a hot environment. It becomes a concern when it happens regularly without an obvious cause, or when it comes with symptoms like dizziness, chest discomfort, or shortness of breath.
The long-term picture is worth paying attention to. A study of patients with high blood pressure found that mortality risk climbed about 7% for every 10 additional beats per minute at rest. People with a resting rate at or above 80 bpm had a 15% higher risk of death compared to those with lower rates, and that risk jumped to 41% higher for those sitting at 100 bpm or above. These numbers don’t mean a single high reading is dangerous, but a consistently elevated resting heart rate is a reliable signal that your cardiovascular system is working harder than it should be.
Too Slow: When a Low Rate Is a Problem
A heart rate below 60 bpm is called bradycardia. For endurance athletes, runners, and people who are generally very fit, a low resting rate is a sign of an efficient heart that pumps more blood per beat. Some healthy adults rest in the 40s or 50s without any issues.
Bradycardia becomes unhealthy when your heart isn’t pumping enough blood to meet your body’s needs. That typically shows up as fatigue, dizziness, lightheadedness, or fainting. A rate below 35 to 40 bpm with any of those symptoms warrants immediate medical attention. Certain medications, particularly those prescribed for high blood pressure and heart rhythm problems, can slow the heart excessively. If you notice a significant drop in your resting rate after starting a new medication, that’s worth flagging.
When Your Heart Can’t Speed Up Enough
There’s a less obvious form of unhealthy heart rate that shows up during exercise rather than at rest. Your maximum heart rate is roughly 220 minus your age, so a 50-year-old would have a predicted max of about 170 bpm. During moderate exercise, your heart should reach 50% to 70% of that number, and during vigorous exercise, 70% to 85%.
Some people’s hearts simply can’t reach those levels. If your heart rate fails to climb to at least 70% to 85% of your age-predicted maximum during peak physical activity, that’s a condition called chronotropic incompetence. It can feel like hitting a wall during exercise: you want to push harder but your body won’t cooperate, you feel unusually winded, or you fatigue much faster than expected. This condition is associated with heart disease and autonomic nervous system dysfunction, and it’s often diagnosed during a stress test.
Heart Rate Variability and What It Reveals
Beyond the number on a pulse reading, the variation between heartbeats carries health information. Your heart doesn’t beat like a metronome. The gaps between beats naturally fluctuate as your nervous system constantly adjusts to your breathing, posture, stress level, and dozens of other inputs. This fluctuation is called heart rate variability, or HRV.
High variability is generally a good sign. It means your body is adaptable, responding fluidly to changing demands. Low variability suggests your system is less resilient. It’s more common in people with diabetes, high blood pressure, asthma, anxiety, and depression. People with higher resting heart rates also tend to have lower HRV, because when the heart beats faster there’s simply less time between beats for variation to occur. Many wearable devices now track HRV, and while a single reading isn’t very meaningful, a consistent downward trend over weeks can reflect declining fitness or increasing stress.
What an Unhealthy Heart Rate Feels Like
An abnormal heart rate doesn’t always produce symptoms. Some people walk around with rates above 100 bpm and feel nothing unusual. Others notice every irregular beat. When symptoms do appear, they typically include a fluttering, pounding, or racing sensation in the chest, sometimes described as feeling like the heart “skipped” a beat. That skipping sensation is often a premature heartbeat, which is usually harmless on its own.
More concerning symptoms include shortness of breath, chest pain or tightness, lightheadedness, sweating, extreme fatigue, and fainting or near-fainting. These suggest the abnormal rate is actually compromising blood flow. If you experience chest pain that spreads to your shoulder, arm, back, neck, or jaw, especially paired with nausea, shortness of breath, or a sudden cold sweat, that’s a potential heart attack. Call emergency services immediately rather than waiting to see if it passes.
Common Causes of Abnormal Heart Rates
Lifestyle factors account for most temporary heart rate spikes. Caffeine, alcohol, nicotine, poor sleep, and emotional stress all push the rate up. Dehydration is a particularly common and underappreciated cause: when blood volume drops, the heart compensates by beating faster. Fever does the same thing, typically adding about 10 bpm for every degree of temperature increase.
Several categories of medication can shift your heart rate in either direction. Blood pressure medications and certain heart drugs can slow it significantly. Stimulants, including caffeine, some ADHD medications, and recreational drugs like cocaine and amphetamines, can cause rapid or irregular rhythms. Some antidepressants, antipsychotics, certain antibiotics, and even asthma inhalers can affect heart rhythm. If your heart rate changes noticeably after starting any new medication, that’s information your prescriber needs.
Underlying medical conditions are the other major driver. Thyroid disorders (an overactive thyroid accelerates the heart, an underactive one slows it), anemia, heart valve problems, and infections can all produce sustained abnormal rates. Sleep apnea is another frequent culprit, often causing nighttime heart rate spikes that people don’t realize are happening.
How to Check Your Own Rate Accurately
The most reliable time to measure your resting heart rate is first thing in the morning, before you get out of bed. Place two fingers on the inside of your wrist below the thumb, or on the side of your neck just below the jawline. Count the beats for 30 seconds and multiply by two. Do this on several different mornings to get a consistent baseline, since a single reading can be thrown off by a bad night’s sleep, a stressful dream, or needing to use the bathroom.
Wrist-based fitness trackers are reasonably accurate for resting heart rate, though they can struggle with readings during high-intensity exercise or if the band is loose. If you’re tracking your rate over time, consistency matters more than precision. Use the same method, at the same time of day, under similar conditions. A resting rate that’s gradually climbing over weeks or months, even if it stays within the “normal” range, is worth paying attention to. It can reflect declining fitness, weight gain, increasing stress, or an emerging health issue.