A resting heart rate that consistently sits above 100 beats per minute is classified as tachycardia, and it almost always has an identifiable cause. For most adults, a normal resting heart rate falls between 60 and 100 bpm, with fitter individuals sometimes dipping as low as 40 bpm. If yours regularly pushes past that upper threshold, or even hovers in the high 80s and 90s in a way that feels unusual for you, something is driving it up.
Make Sure You’re Measuring It Right
Before assuming something is wrong, it’s worth checking that you’re actually capturing your true resting heart rate. Many people glance at their smartwatch after walking around the house, climbing stairs, or drinking coffee and see a number that looks alarming but doesn’t reflect their body at genuine rest.
For an accurate reading, sit or lie down for at least four minutes without moving before you check. Avoid measuring right after exercise, a meal, or caffeine. Your true resting heart rate is actually lowest between about 3 a.m. and 7 a.m., which is why overnight readings from a wearable device tend to be the most reliable baseline. If your activity level in the few hours before measurement was high, that will skew the number upward even if you feel calm.
Everyday Factors That Push Heart Rate Up
The most common reasons for a persistently elevated heart rate aren’t dramatic. They’re the things you do (or don’t do) every day. Caffeine is a stimulant that directly speeds up the heart’s electrical signaling, and the effect can linger for hours depending on how much you consume. Nicotine does the same thing. Dehydration forces your heart to work harder to maintain blood pressure because there’s less fluid volume in your blood vessels, so even mild, chronic underhydration can keep your rate elevated all day.
Stress and poor sleep are two of the biggest culprits. When you’re stressed, your nervous system floods your body with adrenaline, raising your heart rate as part of the fight-or-flight response. That’s supposed to be temporary, but chronic stress, whether from work, relationships, or financial pressure, keeps that system dialed up around the clock. Sleep deprivation compounds the problem by preventing the nervous system from fully resetting overnight. Alcohol is another contributor. Even moderate drinking raises heart rate for hours, and heavy or frequent use can cause more sustained effects.
Low physical fitness also plays a role. When your heart muscle is deconditioned, it pumps less blood per beat and has to beat more often to keep up. This is one of the most reversible causes: regular aerobic exercise gradually strengthens the heart and lowers resting rate over weeks to months.
Medical Conditions That Cause Persistent Tachycardia
If lifestyle factors don’t explain what you’re seeing, several medical conditions can keep your heart rate chronically elevated.
Anemia. When your red blood cell count is low, your blood carries less oxygen per trip through the body. Your heart compensates by beating faster. Iron deficiency is the most common cause, particularly in women with heavy periods, but vitamin deficiencies and chronic illness can also drive it.
Hyperthyroidism. An overactive thyroid gland floods your system with hormones that accelerate your metabolism, including your heart rate. Other signs include unexplained weight loss, feeling hot all the time, trembling hands, and difficulty sleeping.
Fever and infection. Your heart rate rises roughly 10 bpm for every degree of body temperature above normal. Even low-grade infections you might not feel acutely can push your rate up.
Low blood sugar. When blood sugar drops, your body releases stress hormones to mobilize energy, and those hormones speed up the heart.
Electrolyte imbalances. Your heart’s electrical system depends on potassium, sodium, calcium, and magnesium to fire correctly. When any of these are off, whether from sweating heavily, vomiting, poor diet, or certain medications, your heart rhythm and rate can be affected.
Obesity, diabetes, and kidney or lung disease are also established risk factors for tachycardia because they place extra demands on the cardiovascular system.
Anxiety, Panic, or a Heart Problem?
This is one of the trickiest distinctions to make on your own, because anxiety-driven heart rate spikes and actual heart rhythm disorders can feel nearly identical. Both cause a pounding chest, breathlessness, and a sense that something is seriously wrong.
During a panic attack, the rapid heart rate comes from your nervous system flooding the body with adrenaline. The heart itself is beating normally, just faster. In a true arrhythmia like supraventricular tachycardia, the electrical wiring of the heart misfires, often producing rates of 160 to 180 bpm that start and stop abruptly.
A few patterns can help tell them apart. Palpitations lasting less than five minutes are less likely to be a true arrhythmia. A sudden, switch-like onset and offset (one moment you’re fine, the next your heart is racing, and then it stops just as sharply) points more toward an electrical problem in the heart. Anxiety-driven episodes tend to ramp up gradually alongside rising worry and ease as you calm down. If you have a known history of panic disorder, the odds tilt toward anxiety as the cause, but having anxiety doesn’t make you immune to a heart rhythm issue. The only way to know for certain is to capture an ECG during an episode.
Medications That Raise Heart Rate
Several common medications can elevate your resting heart rate as a side effect. Asthma inhalers that contain bronchodilators stimulate the same receptors adrenaline does, and some people notice a noticeably faster heart rate after using them. Decongestants found in cold and allergy medications act as mild stimulants. ADHD medications work by increasing nervous system activity, which often raises heart rate. Certain antidepressants and even some heart rhythm medications can paradoxically increase rate in some people.
If you started noticing your elevated heart rate around the same time you began a new medication, that timing is worth paying attention to. Don’t stop any medication on your own, but bring the observation to your provider.
POTS: When Standing Makes It Worse
If your heart rate jumps dramatically every time you stand up, you may be dealing with postural orthostatic tachycardia syndrome, or POTS. The diagnostic hallmark is a sustained heart rate increase of 30 bpm or more (40 bpm or more for teenagers) within 10 minutes of standing, without a significant drop in blood pressure.
POTS is a disorder of the autonomic nervous system, the part of your body that controls functions you don’t consciously think about, like blood vessel constriction and heart rate adjustments when you change positions. People with POTS often feel dizzy, lightheaded, or fatigued when upright and notice their symptoms improve when lying down. It’s more common in women and frequently develops after a viral illness, surgery, or pregnancy.
What Doctors Check For
When you bring up a persistently high heart rate, a doctor will typically start with an electrocardiogram (ECG), a quick, painless test where sensors on your chest record your heart’s electrical activity. This can reveal abnormal rhythms, structural clues, and whether the fast rate follows a normal pattern or a disordered one.
If the ECG looks normal but you’re still having symptoms, the next step is often a Holter monitor, a small wearable device you take home for a day or more. It continuously records your heart rhythm during your normal routine, catching episodes that a single office ECG might miss. For less frequent episodes, patient-activated recorders or implantable loop recorders can monitor over weeks or months.
Blood work typically includes a thyroid panel, a complete blood count to check for anemia, and electrolyte levels. An echocardiogram uses ultrasound to look at your heart’s structure and how well it pumps. If POTS is suspected, a tilt table test measures how your heart rate and blood pressure respond when you’re shifted from lying down to upright. Stress tests evaluate how your heart handles exercise. In more complex cases, an electrophysiology study threads thin sensors through a blood vessel into the heart to map exactly where abnormal electrical signals originate.
The specific workup depends on your symptoms, age, and what initial tests reveal. For many people, the answer turns out to be something straightforward and treatable, whether that’s an underactive thyroid, dehydration, a medication side effect, or chronic stress that needs better management.