A low heart rate, called bradycardia, means your heart beats fewer than 60 times per minute at rest. A normal resting heart rate for adults falls between 60 and 100 beats per minute (bpm). But dropping below 60 bpm isn’t automatically a problem. For many people, especially those who are physically active, a resting rate in the 50s or even 40s is a sign of a healthy, efficient heart.
When a Low Heart Rate Is Normal
Your heart rate naturally fluctuates throughout the day, and several situations can push it well below 60 bpm without any cause for concern.
Fitness is the most common reason. Well-trained endurance athletes routinely have resting heart rates in the 40s. Regular vigorous exercise strengthens the heart muscle so it pumps more blood with each beat, meaning it doesn’t need to beat as often to meet the body’s demands. If you run, cycle, swim, or do other sustained cardio several times a week, a rate in the low 50s or high 40s can be perfectly healthy.
Sleep is another. During the night, your heart rate drops significantly as your body’s demand for oxygen decreases. A healthy adult’s sleeping heart rate typically falls between 40 and 60 bpm. This is normal physiology, not a sign of a problem. If a fitness tracker alerts you to a low heart rate at 3 a.m., that’s likely just your body doing what it should.
Symptoms That Signal a Problem
A low heart rate becomes a medical concern when your heart isn’t pumping enough blood to keep up with your body’s needs. The key distinction isn’t the number alone; it’s whether you’re feeling the effects. Symptoms of problematic bradycardia include:
- Dizziness or lightheadedness, especially when standing up
- Fatigue that doesn’t match your activity level
- Shortness of breath during mild exertion
- Fainting or near-fainting episodes
- Confusion or difficulty concentrating
- Chest discomfort
If you have a resting rate below 60 but feel fine, exercise without trouble, and have no episodes of dizziness or fainting, your heart is likely just efficient. If you’re experiencing any of the symptoms above, the rate matters more, even if it’s only slightly below 60.
Common Causes of Bradycardia
When a low heart rate does indicate something wrong, several categories of causes are worth understanding.
Electrical system problems. Your heart has a built-in pacemaker (the sinus node) that generates the electrical signals telling it when to beat. If that node malfunctions or if the signals get blocked on their way through the heart, the rate slows. This is more common with aging, as the heart’s electrical pathways can gradually deteriorate.
Medications. Several widely prescribed drugs lower heart rate as either their intended effect or a side effect. Beta-blockers (commonly prescribed for high blood pressure and heart conditions) are the most frequent culprits. Calcium channel blockers like diltiazem and verapamil also slow heart rate. Some antidepressants, certain heart rhythm medications, and even some eye drops containing beta-blockers can contribute. If you started a new medication and noticed your heart rate dropping or began feeling sluggish or dizzy, the drug could be responsible.
Thyroid dysfunction. An underactive thyroid slows metabolism across the body, including heart rate. This is one of the first things doctors check with a blood test when evaluating bradycardia.
Sleep apnea. Repeated pauses in breathing during sleep can trigger changes in heart rhythm, including bradycardia. People with obstructive sleep apnea often don’t know they have it, so unexplained slow heart rate can sometimes be the clue that leads to diagnosis.
Other medical conditions. Heart attack, infection, and electrolyte imbalances (particularly abnormal potassium levels) can all slow the heart. These tend to cause more acute, noticeable symptoms.
How Bradycardia Is Diagnosed
An electrocardiogram (ECG or EKG) is the primary test. It records your heart’s electrical activity through sensors placed on your chest and takes only a few minutes. The tracing shows whether the heart’s rhythm is normal and where any signal delays or blocks are occurring.
The challenge is that bradycardia can come and go. If your resting ECG looks normal but you’re having intermittent symptoms, your doctor may have you wear a portable heart monitor. A Holter monitor records continuously for 24 hours or more. An event recorder works differently: you wear it for up to 30 days and press a button when symptoms occur, capturing what your heart is doing at that exact moment.
Other tests serve specific purposes. A blood draw checks thyroid function and electrolyte levels. A tilt table test is used if you’ve been fainting; it monitors your heart rate and blood pressure as a table tilts you from lying flat to a standing position. An exercise stress test checks whether your heart rate responds appropriately to physical demand. A sleep study may be ordered if sleep apnea is suspected.
How Low Heart Rate Is Treated
Treatment depends entirely on the cause. If a medication is responsible, adjusting the dose or switching to a different drug often resolves the issue. If an underactive thyroid is driving the slow rate, treating the thyroid corrects the heart rate as well. Sleep apnea treatment can eliminate bradycardia episodes that happen during the night.
When the cause is a permanent problem with the heart’s electrical system and symptoms are present, a pacemaker is the standard treatment. This small device is implanted under the skin near the collarbone and sends electrical impulses to keep your heart beating at an adequate rate. Before recommending a permanent pacemaker, doctors first rule out all reversible causes and confirm that symptoms clearly correlate with the slow heart rate. The procedure itself is relatively minor, and most people go home the same day or the next.
A pacemaker is typically considered when there’s a complete block in the heart’s electrical pathway, when the heart’s natural pacemaker is failing and causing symptoms like fainting or significant fatigue, or when a necessary medication is causing bradycardia that can’t otherwise be managed.
Heart Rate Ranges in Children
What counts as “low” changes dramatically with age. Children have naturally faster heart rates than adults, so the 60 bpm threshold doesn’t apply to young kids. Newborns normally have an awake heart rate between 85 and 205 bpm. Toddlers (3 months to 2 years) range from 100 to 190 bpm while awake. Children ages 2 to 10 fall between 60 and 140 bpm. Only after age 10 does the adult range of 60 to 100 bpm apply. A heart rate of 55 in a toddler is a very different situation than 55 in a teenager.