A fast heart rate, known as tachycardia, is often harmless and can happen due to stress, anxiety, vigorous exercise, or high caffeine intake. It may also occur during pregnancy or when taking thermogenic supplements, as well as certain cold, allergy, or asthma medications.
Sometimes, a rapid heart rate can be linked to underlying health issues such as arrhythmias, other heart conditions, an overactive thyroid (hyperthyroidism), or lung problems like a pulmonary embolism. If your heart races frequently, takes a long time to slow down, or occurs alongside shortness of breath, dizziness, or fainting, you should seek medical evaluation.
The underlying cause is usually determined by considering possible triggers, related symptoms, and results from tests such as an ECG or bloodwork. Treatment varies depending on the cause and may involve lifestyle changes, anxiety or stress management, adjusting stimulant use or medications, and specific medical treatments like beta-blockers or specialist care.
What causes a fast heart rate?
The main causes of a fast heart rate include:
1. Intense physical activity
It’s normal for your heart rate to rise during or after intense physical activities such as volleyball, basketball, or soccer. When your body is active, your heart works harder to deliver enough blood, oxygen, and nutrients to your muscles and brain.
Typically, the maximum heart rate for men is estimated at 220 minus their age, while for women it’s about 226 minus their age.
What to do: Monitor your heart rate while you are exercising, either manually or with a smart watch that measures your pulse. If your heart rate goes above what it should be, or if you experience symptoms like weakness, dizziness, general malaise, or chest pain, you should seek medical attention immediately.
It is also important to be assessed by a healthcare provider before starting any new physical activity.
2. Excess stress
An increased heart rate is also one of the main symptoms of stress. It is the body’s natural response to a threatening situation, along with increased respiratory rate, muscle contraction, and an increase in blood pressure.
However, when stress becomes chronic, it can disrupt cortisol levels and cause symptoms such as hair loss, irritability, dizziness, acne, headaches, body aches, and insomnia.
What to do: It’s important to recognize where your stress is coming from, whether it’s related to work, school, or family issues. Try to make time for activities that bring you joy, such as spending time with friends, exercising, or enjoying a hobby like photography or sewing.
Talking with a therapist can also help you build self-awareness and emotional stability, both of which can reduce stress.
3. Anxiety
Anxiety can arise in response to everyday stressors such as public speaking, job interviews, or exams. It often involves symptoms like a rapid heartbeat, shortness of breath, trembling, or feelings of fear. However, when anxiety becomes persistent or overwhelming, it may develop into a condition such as generalized anxiety disorder or panic disorder.
Read more about anxiety attacks and how to identify one.
What to do: The most effective way to manage anxiety and reduce a rapid heart rate is to speak with a mental health professional. They can help identify the root cause of your anxiety and suggest appropriate treatments.
Engaging in relaxing activities, such as meditation, regular exercise, and maintaining a healthy diet can also help ease anxiety. Check out our list of teas for anxiety that may help calm your nerves and support your treatment plan.
4. Cardiac problems
Many heart problems are linked to a rapid heartbeat, which is why an unusually fast heart rate can signal an underlying cardiac issue.
Arrhythmias that cause increased pulse rates occur when the heart’s electrical signals are disrupted. These abnormalities may also produce symptoms such as dizziness, fatigue, nausea, or fainting. Other conditions that can lead to a rapid heart rate include myocardial infarction (heart attack), stroke, heart failure, and myocarditis.
Additionally, diseases affecting other body systems, such as thyroid disorders, hormonal imbalances, or infections, can also influence heart function.
What to do: If you experience symptoms such as a rapid heartbeat, dizziness, weakness, shortness of breath, or chest pain, go to the emergency room immediately.
Heart rhythm problems should be evaluated and managed by a cardiologist to ensure you receive the most appropriate treatment. In some cases, a procedure called an ablation may be needed to correct the overactive area of the heart responsible for the arrhythmia.
5. Hyperthyroidism
The thyroid is a gland that produces hormones that regulate many body functions. When it produces too many hormones, a condition called hyperthyroidism occurs.
Common symptoms of hyperthyroidism include a rapid heart rate, elevated blood pressure, nervousness, anxiety, insomnia, and weight loss.
Learn more about how to identify symptoms of thyroid problems.
What to do: If hyperthyroidism is confirmed, you should consult an endocrinologist for treatment and ongoing monitoring. Treatment may include beta-blockers (such as propranolol or metoprolol) and medications that reduce thyroid hormone levels.
It’s also important to follow a balanced diet as recommended by a registered dietitian, since certain foods can provide nutrients that support healthy thyroid function.
6. Lung problems
When respiratory problems occur, the heart rate often increases as the heart works harder to compensate for reduced oxygen levels and ensure that enough oxygen reaches all tissues. One lung condition that can cause a rapid heart rate is a pulmonary embolism, which happens when a blood clot blocks a blood vessel in the lungs.
Symptoms of a pulmonary embolism include shortness of breath, coughing, chest pain, dizziness, and excessive sweating. This condition may develop in people with heart disease, cancer, clotting disorders, following surgery, or as a complication of illnesses such as COVID-19.
What to do: A pulmonary embolism is a life-threatening condition, so you should go to the hospital right away if you experience any of these symptoms.
7. Thermogenic supplements
Thermogenic supplements are often used for weight loss or to enhance performance during exercise. They work by increasing the body’s core temperature and speeding up the metabolism. These supplements can impact the heart and may cause a rapid heartbeat, anxiety, irritability, or trouble sleeping.
What to do: Avoid using thermogenic supplements without guidance from a registered dietitian. To burn more calories and fat during exercise, calculate your fat-burning heart rate, which is 70-80% of your maximum heart rate.
Before starting any new workout routine, it’s important to see your primary care provider for a physical assessment.
8. Medication use
Some medications to treat the cold or flu, rhinitis, allergies, bronchitis, or asthma can contain substances like pseudoephedrine, oxymetazoline, phenylephrine, or salbutamol. These substances can cause side effects including a fast heart rate.
What to do: If you notice a rapid heart rate after taking any of the above medications, stop using them right away. If your heart rate doesn’t return to normal, seek medical attention immediately. These medications should only be used under the guidance of a healthcare provider following a proper physical assessment.
9. Pregnancy
A faster heart rate is common during pregnancy. It happens because the body undergoes natural changes that help deliver more oxygen and nutrients to the baby.
What to do: Treatment is usually not necessary, however you should attend all prenatal appointments with your OBGYN or midwife to ensure that mother and baby are healthy.
Maintaining a balanced diet, limiting caffeine, and doing light physical activity (such as walking or water aerobics) are also recommended. People with a history of heart problems should see a cardiologist before becoming pregnant.