Your heart may beat fast while you are resting because of stress, caffeine, nicotine, dehydration, fever, pain, or some medicines. A fast pulse can also be linked to conditions such as anemia, an overactive thyroid, or an abnormal heart rhythm. For many adults, a resting rate above 100 beats per minute is considered fast, but the number alone cannot explain the cause.
What Counts as a Fast Heart Rate at Rest?
For most adults, a normal resting heart rate is between 60 and 100 beats per minute. A resting rate above 100 beats per minute is generally called tachycardia. However, your usual heart rate can depend on factors such as your age, physical fitness, health, and medicines. Children's normal heart rates also vary by age, so the adult range should not be used to assess a child's heartbeat.
Resting means you are sitting or lying comfortably rather than exercising or recovering immediately after physical activity. If you have just walked upstairs, rushed somewhere, or experienced a stressful event, your heart rate may take time to settle. The American Heart Association explains that tachycardia describes a heart rate that is too fast at rest, although the significance of a particular rate depends on the person's circumstances.
A single high reading does not necessarily mean something is wrong with your heart. It is more useful to consider whether the rate settles after resting, whether the episodes keep returning, and whether you experience other symptoms.
Why Might Your Heart Race When You Are Not Active?
Your heart responds to signals from your nervous system, hormones, medicines, and changes in your body's needs. Some triggers cause a temporary increase in heart rate, while others may point to a medical condition that needs attention.
Everyday triggers that can raise your heart rate
Common reasons for a fast or noticeable heartbeat include:
- Stress and anxiety: Emotional stress can activate the body's response to a perceived threat and make your heart beat faster, even when you are sitting quietly.
- Caffeine and nicotine: Coffee, energy drinks, tobacco, and other nicotine products may trigger a racing or pounding heartbeat in some people.
- Alcohol and recreational stimulants: Alcohol and stimulant drugs can affect heart rate or rhythm.
- Fever, pain, or infection: These can increase the body's demands and cause the heart to beat faster.
- Dehydration: Not having enough fluid in your body can contribute to a rapid pulse.
- Poor sleep: Inadequate sleep may be associated with episodes of a noticeable or racing heartbeat.
- Medicines: Some cold and allergy remedies, asthma medicines, and other drugs may increase heart rate or cause palpitations. The effect depends on the medicine and the individual.
- Hormonal changes: Pregnancy, menstruation, and menopause can be associated with palpitations in some people.
According to Mayo Clinic, stress, certain stimulants, fever, hormonal changes, and thyroid hormone levels are among the factors associated with heart palpitations. Sometimes no clear trigger is found.
Medical conditions that may cause a fast heartbeat
A fast heart rate at rest can also occur when an underlying health problem affects the body's circulation, metabolism, or electrical control of the heart. Possible causes include:
- Anemia: A low level of healthy red blood cells or hemoglobin can be associated with a faster heartbeat.
- An overactive thyroid: Excess thyroid hormone can increase the heart rate and contribute to palpitations.
- Heart rhythm disorders: Problems with the electrical signals that control the heartbeat may cause the heart to beat too quickly or irregularly.
- Heart disease: Certain problems involving the heart muscle, valves, or electrical system can lead to a rapid heartbeat.
- Low blood pressure or significant blood loss: In some circumstances, the heart beats faster as the body tries to maintain blood flow.
- Other illnesses: Infections and some lung conditions can also be associated with a raised heart rate.
These possibilities cannot be distinguished by pulse rate alone. A clinician may consider your medical history, recent illness, medications, symptoms, and examination findings to understand which explanations are relevant.
What Does a Fast Heartbeat Feel Like?
Some people notice their heart beating unusually quickly, while others feel an uncomfortable pounding or fluttering even when the rate is not especially high. The term palpitations describes the sensation of being unusually aware of your heartbeat; it does not automatically mean that the heart's rhythm is abnormal.
The NHS describes palpitations as sensations that may involve racing, pounding, fluttering, or skipped beats. They can last for seconds or minutes, or sometimes longer. Experiences that may accompany a fast heartbeat include:
- A racing or pounding sensation in the chest
- A fluttering feeling or the impression that the heart has skipped a beat
- A heartbeat that feels irregular
- Dizziness or lightheadedness
- Unusual tiredness or weakness
- Shortness of breath or chest discomfort
These symptoms can occur for different reasons and do not establish a diagnosis. Their timing, duration, pattern, and associated symptoms help determine whether further assessment is needed.
When Is a Fast Heartbeat at Rest an Emergency?
A racing heart can be temporary, but certain accompanying symptoms require immediate medical attention. Seek emergency care if a fast or pounding heartbeat occurs with any of the following:
- Chest pain, pressure, or significant discomfort
- Severe shortness of breath
- Fainting or feeling as though you are about to faint
- Severe dizziness or sudden collapse
If these symptoms are happening now, call your local emergency number rather than waiting for the heartbeat to settle or attempting to travel to care yourself. A rapid or irregular heartbeat accompanied by these warning signs may reflect a potentially serious problem.
If the episode stops but you experienced chest pain, fainting, or significant breathing difficulty, seek urgent medical assessment even if you feel better now.
When Should You See a Doctor About a Fast Pulse?
Arrange a medical appointment if your heart repeatedly beats fast while you are resting, episodes are becoming more frequent, a racing sensation lasts longer than a few minutes, or the changes are new or difficult to explain. It is particularly important to seek assessment if you have an existing heart condition or a family history of heart problems.
A resting pulse that remains above 100 beats per minute without an obvious temporary explanation, such as recent exercise, fever, or acute stress, also deserves medical evaluation. The appropriate level of urgency depends on your symptoms, the pattern of the heartbeat, and your overall health.
For children, seek advice from a pediatric healthcare professional when a fast heartbeat is persistent, recurrent, or accompanied by concerning symptoms. Heart rate norms and the interpretation of symptoms differ with age.
How Do Doctors Find the Cause of a Fast Heartbeat?
Your clinician will usually start by asking when the episodes happen, how long they last, whether the heartbeat feels regular, and whether anything seems to trigger them. They may also review your medical history, medicines, caffeine and alcohol intake, and any symptoms that occur alongside the racing heartbeat.
Depending on your circumstances, the assessment may include:
- Pulse and physical examination: To assess your heart rate and rhythm and look for signs that may help explain the symptoms.
- Electrocardiogram (ECG or EKG): This records the heart's electrical activity and can help identify an abnormal rhythm.
- Portable heart monitoring: A Holter monitor or event monitor may record your heartbeat over a longer period if episodes come and go and are not captured during an appointment.
- Blood tests: Depending on the suspected cause, tests may check for anemia, thyroid problems, or changes in electrolytes and other substances in the blood.
- Additional heart tests: An echocardiogram or other investigation may be recommended when the history, examination, or initial results suggest it is necessary.
MedlinePlus lists ECG testing, longer-term heart monitoring, blood tests, and other investigations among the tests clinicians may use when evaluating tachycardia. Not everyone needs every test. The choice depends on the information gathered during the assessment and whether an episode has been captured.
What Can You Do When Your Heart Starts Racing at Rest?
If you are otherwise feeling well and have no emergency warning signs, stop what you are doing and sit or lie down comfortably. Allow yourself to rest for several minutes. If you can do so without delaying necessary care, check your pulse and note whether it seems regular or irregular.
Pay attention to the time the episode began, how long it lasted, what you were doing beforehand, and whether you had recently consumed caffeine, used nicotine, taken a new medicine, or been ill. These details may help your clinician identify a pattern. A smartwatch or fitness tracker can provide useful recorded measurements, but its reading alone cannot confirm the cause or diagnose an abnormal heart rhythm.
While waiting for medical advice, consider practical steps that may reduce common triggers:
- Limit caffeine and energy drinks if they seem to trigger episodes.
- Avoid nicotine and recreational stimulant drugs.
- Drink fluids if dehydration may be contributing and you have not been advised to restrict fluids.
- Prioritize adequate sleep and use gentle relaxation techniques to manage stress.
- Ask a pharmacist or clinician whether any prescription or non-prescription medicine could be affecting your heartbeat.
Do not stop prescribed medicines, change doses, or take someone else's heart medication to slow your pulse without medical guidance. If the heartbeat continues, keeps returning, or is accompanied by warning signs, seek appropriate medical care instead of relying on home measures.
How Is a Fast Heartbeat Treated?
Treatment depends on what is causing the rapid heartbeat. When it is related to a temporary trigger, addressing that trigger may be enough. If a medicine contributes to the problem, a clinician may consider changing the dose or choosing an alternative when appropriate. Conditions such as anemia, thyroid disorders, infections, or other underlying illnesses need care directed at the specific cause.
If testing identifies an abnormal heart rhythm, treatment depends on the type of rhythm, the symptoms it causes, and the person's overall heart health. Options may include medication, a heart procedure, or other specialist treatment. A fast pulse should not automatically be treated by simply slowing the heart rate, because it can sometimes be the body's response to another problem that also needs attention.
The most useful next step is to understand the pattern and context of your symptoms. Occasional palpitations may not require treatment, but repeated, persistent, worsening, or unexplained episodes are worth discussing with a healthcare professional.