A resting heart rate above 100 beats per minute (bpm) is considered elevated in adults. The medical term for this is tachycardia, and it marks the upper boundary of the normal resting range of 60 to 100 bpm. A single reading above 100 after climbing stairs or drinking coffee isn’t necessarily a concern, but a resting heart rate that consistently stays above that threshold signals something worth paying attention to.
Normal Resting Heart Rate by Age
The 60 to 100 bpm range applies to adults aged 18 and older, but normal looks very different in children. Newborns run between 100 and 205 bpm. Infants stay in the 100 to 180 range. By the toddler years, the range narrows to about 98 to 140, and school-age children (5 to 12) typically fall between 75 and 118 bpm. Teenagers settle into the adult range of 60 to 100.
Athletes often sit well below the standard range, with resting rates in the 40s or 50s. This happens because regular endurance training strengthens the heart muscle, allowing it to pump more blood per beat. A low resting rate in a fit person is a sign of cardiovascular efficiency, not a problem.
“Resting” means you’re sitting or lying down while awake. Your heart rate drops further during sleep and rises during any physical activity, so the context of when you check matters.
Common Causes of an Elevated Rate
Plenty of everyday factors push your heart rate above 100 without any underlying heart condition. Caffeine, nicotine, dehydration, stress, anxiety, poor sleep, and fever all raise your resting rate temporarily. So do certain medications, including decongestants and some asthma inhalers. In most of these cases, the elevation resolves once the trigger passes.
Sustained tachycardia that isn’t explained by an obvious trigger can point to medical causes. These include thyroid problems (an overactive thyroid accelerates your metabolism and heart rate), anemia (your heart compensates for fewer oxygen-carrying red blood cells by beating faster), and heart rhythm disorders. Chronic dehydration is an underappreciated contributor: when blood volume drops, the heart speeds up to maintain circulation.
When a Fast Heart Rate Is a Rhythm Problem
Not all elevated heart rates feel or behave the same way. Two of the most common rhythm disorders that cause a fast heart rate originate in the upper chambers of the heart, but they differ in important ways.
Atrial fibrillation (afib) produces a rapid, irregular rhythm. The upper chamber fires chaotic electrical signals over 300 times per minute, causing it to quiver instead of contracting normally. Afib primarily affects people 65 and older. Because blood can pool in the upper chambers when they aren’t squeezing properly, afib carries a risk of blood clots, and treatment often includes blood-thinning medication alongside heart rate control.
Supraventricular tachycardia (SVT) is a different pattern. It produces a very fast but regular rhythm that can reach 200 bpm. SVT can strike at any age, with an average age of diagnosis around 45. Episodes may last only a few seconds and feel like a flutter or flip-flop in the chest. If an episode persists for more than a few minutes, the heart doesn’t have time to fill completely between beats, which can cause dizziness, lightheadedness, or shortness of breath. SVT can sometimes be interrupted with simple physical maneuvers like coughing or bearing down.
How to Check Your Heart Rate Accurately
The easiest place to find your pulse is your wrist. Turn one hand palm-up and place three fingers from your other hand on the groove just below where your thumb meets your wrist. Press firmly until you feel a steady beat. If you prefer the neck, place your index and middle fingers in the groove beside your windpipe, just under the jawline.
Count the beats for 30 seconds, then double the number to get your beats per minute. For a quicker check, count for 10 seconds and multiply by six. A clock or stopwatch helps keep your count accurate. Smartwatches and fitness trackers give a reasonable estimate for trends over time, but a manual check is useful when you want to confirm a reading or your device seems off.
For the most reliable resting measurement, sit quietly for at least five minutes before checking. Avoid measuring right after exercise, a meal, or caffeine.
Elevated Heart Rate During Exercise
Your heart rate is supposed to rise during physical activity, and the numbers that count as “elevated” shift dramatically. The American Heart Association defines moderate-intensity exercise as 50 to 70% of your maximum heart rate, and vigorous exercise as 70 to 85%.
Maximum heart rate is most commonly estimated with the formula 220 minus your age. A more refined version, developed through a large meta-analysis, uses 208 minus 0.7 times your age. Neither formula is perfectly accurate for every individual, but they provide a useful ballpark. For a 40-year-old, the classic formula gives a max of 180 bpm, meaning moderate exercise would target roughly 90 to 126 bpm and vigorous exercise 126 to 153 bpm. These numbers are guidelines, not hard limits.
Signs That Deserve Attention
An elevated heart rate alone doesn’t always mean something is wrong. But certain accompanying symptoms change the picture. Chest pain or pressure, fainting or near-fainting, severe shortness of breath at rest, and a heart rate that stays above 100 bpm for hours without an obvious explanation are all worth taking seriously. The same goes for a resting heart rate that has gradually crept upward over weeks or months, especially if you haven’t changed your activity level, caffeine intake, or stress load.
Episodes of sudden, dramatic heart rate spikes, where your pulse jumps to 150 or above while you’re sitting still, are characteristic of rhythm disorders like SVT. If these episodes are brief and rare, they may be harmless, but a pattern of recurring episodes warrants evaluation. An electrocardiogram (a painless test that records your heart’s electrical activity) is typically the first step in sorting out whether a fast heart rate is coming from a rhythm problem or a non-cardiac cause.