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Tachycardia: what a fast heart rate means
Key takeaways
- Tachycardia means a heart rate above 100 beats per minute at rest in adults.
- Most often it is sinus tachycardia — a normal response to fever, dehydration, stress, caffeine or exercise.
- Some types, such as SVT, atrial fibrillation or ventricular tachycardia, are heart rhythm problems that need diagnosis with an ECG.
- Fast heartbeat with chest pain, fainting or shortness of breath: call 911.
What is tachycardia?
A normal resting heart rate for adults is 60–100 bpm (American Heart Association). Tachycardia is a rate above 100 bpm while resting. During exercise a high rate is expected — see target heart rate by age.
Types of tachycardia
| Type | Where it starts | What it's like |
|---|---|---|
| Sinus tachycardia | The heart's normal pacemaker | Regular, rises and falls gradually; usually a response to something (fever, stress, anemia) |
| Supraventricular tachycardia (SVT) | Above the ventricles | Sudden on/off racing, often 150–250 bpm |
| Atrial fibrillation (AFib) | Upper chambers (atria) | Irregular and often fast; raises stroke risk |
| Atrial flutter | Atria | Fast, usually regular |
| Ventricular tachycardia (VT) | Lower chambers | Can be life-threatening; often with heart disease |
| POTS | Nervous-system regulation | Heart rate jumps 30+ bpm within 10 minutes of standing, with dizziness |
Common causes
- Fever and infection — heart rate often rises about 10 bpm for each 1 °C of fever (see flu symptoms)
- Dehydration, blood loss, anemia
- Anxiety, panic, pain, poor sleep
- Caffeine, nicotine, alcohol, energy drinks
- Medicines: decongestants, asthma inhalers, thyroid medicine, and stimulant ADHD medications
- Overactive thyroid (hyperthyroidism)
- Low blood sugar and low blood pressure
- Heart conditions: heart failure, previous heart attack, valve disease, inherited rhythm disorders
Symptoms
- Racing, pounding or fluttering heartbeat (palpitations)
- Shortness of breath
- Dizziness or light-headedness
- Chest discomfort
- Fatigue, reduced exercise tolerance
- Fainting (syncope)
Some people feel nothing and find out from a watch, a phone reading or a doctor's visit.
When a fast heart rate is an emergency
Call 911 if a fast heartbeat comes with chest pain or pressure, fainting, severe shortness of breath, confusion, or weakness on one side. Seek prompt care if your resting heart rate stays above 120 bpm without an obvious cause, or if episodes start and stop suddenly.
How tachycardia is diagnosed and treated
Diagnosis needs an ECG — often a Holter or event monitor to catch episodes — plus blood tests (thyroid, blood count, electrolytes). Treatment depends on the type: fixing the trigger for sinus tachycardia; vagal maneuvers, medicines or catheter ablation for SVT; rate control and stroke prevention for AFib; and specialist care for VT.
Know your normal
A single high number means little; a trend means a lot. Cardivo measures heart rate and HRV from your fingertip on the iPhone camera in about 30 seconds — no watch needed — so you can check during a racing episode and log it with how you feel. Camera readings help you see trends; they do not diagnose rhythm problems — only an ECG can. Read more in high resting heart rate and resting heart rate.
This guide is general wellness education based on the public sources below. It is not medical advice, diagnosis, or treatment. Cardivo is not a medical device. If you think you are having a medical emergency, call 911.
Frequently asked questions
What heart rate is considered tachycardia?
For adults, a resting heart rate above 100 beats per minute is tachycardia.
Is tachycardia dangerous?
Sinus tachycardia from fever, exercise or stress is usually harmless and goes away with the cause. Rhythm problems such as SVT, atrial fibrillation or ventricular tachycardia need medical evaluation, and a fast heart rate with chest pain, fainting or shortness of breath is an emergency.
What causes sudden tachycardia?
Common triggers include fever, dehydration, anxiety, caffeine, alcohol, stimulant medicines, low blood sugar and thyroid problems. A sudden start-and-stop racing heartbeat can be SVT.
Sources
- American Heart Association — Tachycardia: fast heart rate
- Cleveland Clinic — Tachycardia
- American Heart Association — Target heart rates