For adults, a resting heart rate above 100 beats per minute is considered too high. That threshold has a medical name, tachycardia, and it applies whether you’re sitting on the couch or lying in bed. During exercise, the upper limit depends on your age, but pushing past 85% of your estimated maximum heart rate moves you beyond recommended training zones.
Those numbers are starting points. What counts as “too high” also depends on your age, your fitness level, what you’re doing at the time, and whether you’re experiencing symptoms. Here’s how to make sense of all of it.
Normal Resting Heart Rate by Age
A healthy resting heart rate for adults and teens (age 13 and up) falls between 60 and 100 beats per minute. Children naturally run higher because their hearts are smaller and need to pump faster to circulate the same volume of blood. Here’s what’s typical at each stage:
- Newborns (birth to 4 weeks): 100 to 205 bpm
- Infants (4 weeks to 1 year): 100 to 180 bpm
- Toddlers (1 to 3 years): 98 to 140 bpm
- Preschoolers (3 to 5 years): 80 to 120 bpm
- School-age children (5 to 12 years): 75 to 118 bpm
- Teens and adults (13+): 60 to 100 bpm
These ranges apply when you’re awake and at rest. Your heart rate drops during sleep and rises with any physical activity, emotional stress, or even digestion. Well-trained athletes often have resting rates in the 40s or 50s because their hearts pump more blood per beat, so fewer beats are needed.
Why Your Heart Rate Might Be Too High at Rest
A resting heart rate above 100 bpm doesn’t always mean something is wrong with your heart. In most cases, your heart is responding normally to something else going on in your body. Common, everyday triggers include fever, dehydration, nervousness, fear, caffeine, and certain medications (especially decongestants and stimulants). Intense exercise within the last hour or two can also keep your rate elevated for a while after you stop moving.
Less common but more serious causes include anemia (when your blood carries less oxygen, so your heart compensates by beating faster), an overactive thyroid gland, heavy bleeding, and damage to the heart muscle itself. These tend to produce a persistently elevated heart rate rather than a temporary spike, and they usually come with other noticeable symptoms like fatigue, weight changes, or feeling winded during activities that used to feel easy.
The key distinction is between a heart rate that’s high because your body is reacting to a stressor, and one that’s high because of a problem with your heart’s electrical system. The first type, sometimes called sinus tachycardia, usually resolves when the trigger goes away. The second type involves irregular rhythms or misfiring electrical signals, and it tends to come on suddenly, without an obvious cause.
What Counts as Too High During Exercise
Your heart rate is supposed to climb when you exercise. The question is how high is safe. The most common way to estimate your personal ceiling is to subtract your age from 220. A 40-year-old, for example, gets an estimated maximum of 180 bpm. A slightly more refined formula, developed by researcher Hirofumi Tanaka, uses 208 minus 0.7 times your age, which gives that same 40-year-old a max of about 180 as well.
Neither formula is precise for any individual. Studies have found that the classic 220-minus-age formula can be off by roughly 14 bpm in either direction, and the Tanaka formula by about 11 bpm. Both tend to overestimate true maximum heart rate, particularly in younger adults. They’re useful as rough guides, not hard limits.
The American Heart Association recommends staying within these zones during workouts:
- Moderate intensity: 50% to 70% of your estimated max
- Vigorous intensity: 70% to 85% of your estimated max
For that 40-year-old with an estimated max of 180, moderate exercise means a heart rate between 90 and 126 bpm, and vigorous exercise tops out around 153 bpm. Going above 85% of your max isn’t inherently dangerous for healthy people, but it’s unsustainable for long periods and increases the risk of overexertion. If you have any heart condition, your safe upper limit may be significantly lower.
Symptoms That Signal a Problem
A number on a heart rate monitor matters less than how you feel. Plenty of people briefly hit 110 bpm from climbing stairs or a stressful phone call and feel completely fine. That’s not a medical concern. The combination of a high heart rate plus certain symptoms is what shifts the picture.
Pay attention if a fast heart rate comes with chest pain or tightness, dizziness or lightheadedness, fainting or near-fainting, significant shortness of breath at rest, or a fluttering or pounding sensation in your chest that starts and stops abruptly. These signs suggest your heart may not be pumping blood effectively, either because the rate is too fast for the chambers to fill properly or because the rhythm itself has become disorganized.
A heart rate that suddenly jumps to 150 or higher while you’re sitting still, especially if it feels like a switch flipped rather than a gradual increase, is worth taking seriously even if it resolves on its own. Episodes like that can point to an electrical rhythm problem that tends to recur.
What Happens When a High Heart Rate Persists
A fast heart rate that lasts hours, days, or weeks puts real strain on the heart. When the heart beats too quickly for too long, it doesn’t have enough time between beats to fill with blood. That means each contraction pushes out less blood than normal, and the rest of the body gets shortchanged on oxygen and nutrients.
Over time, this can weaken the heart muscle itself, a condition called tachycardia-induced cardiomyopathy. The heart becomes enlarged and less efficient at pumping. It can also raise the risk of blood clots forming in the heart’s chambers, particularly in people with certain rhythm disorders like atrial fibrillation, where the target for rate control is generally keeping the heart below 110 bpm. Left truly untreated for months or years, chronic tachycardia can progress to heart failure.
The encouraging part: tachycardia-induced cardiomyopathy is often reversible. Once the heart rate is brought under control, the heart muscle can recover much or all of its function.
How to Check Your Heart Rate at Home
You don’t need a device to get an accurate reading. Turn one hand palm-up and place the tips of your index and middle fingers on the inside of the opposite wrist, between the bone and the tendon on the thumb side. Press lightly until you feel each beat. Pressing too hard can actually block the blood flow and make the pulse harder to find.
Count the beats for a full 60 seconds for the most accurate result. If you’re in a hurry, count for 15 seconds and multiply by four. Check your pulse first thing in the morning, before getting out of bed, for the truest resting rate. Caffeine, a recent meal, or even standing up can bump it higher.
Smartwatches and fitness trackers use optical sensors that work well for resting measurements but can be less reliable during exercise or if the band is loose. If your device consistently shows a resting rate above 100 bpm and you haven’t just been active or stressed, it’s worth confirming with a manual check and bringing it up with your doctor.