Yes, metoprolol can cause a low heart rate. Slowing the heart is actually one of the drug’s primary effects, not an unintended side effect. A resting heart rate below 60 beats per minute is considered bradycardia, and metoprolol achieves its therapeutic benefit partly by reducing how fast the heart beats. The question isn’t really whether it can slow your heart, but when that slowing crosses from helpful into problematic.
How Metoprolol Slows the Heart
Metoprolol works by blocking beta-1 receptors, which are concentrated in the heart. These receptors normally respond to adrenaline and related stress hormones by telling the heart to beat faster and harder. When metoprolol sits on those receptors, it blocks that signal. The heart’s natural pacemaker fires more slowly, and electrical signals travel through the heart at a reduced pace.
This is the entire reason metoprolol is prescribed for conditions like high blood pressure, heart failure, and certain irregular heart rhythms. The heart rate reduction is intentional. But the same mechanism that makes the drug effective can sometimes push the heart rate lower than intended.
How Common Is It?
In large clinical trials, the incidence of bradycardia with metoprolol ranges from about 1% to 9%. The formulation matters. The immediate-release version (metoprolol tartrate) causes bradycardia at roughly twice the rate of the extended-release version (metoprolol succinate): 24.1 events per 1,000 person-years compared to 12.9 per 1,000 person-years in one large study. The extended-release form delivers the drug more gradually, which likely explains the lower rate.
These numbers represent clinically significant bradycardia, not just a slightly lower resting rate. Many people on metoprolol will notice their heart rate dip into the mid-50s or even high 40s without experiencing any symptoms at all. A heart rate between 40 and 60 is common in healthy, physically active people even without medication.
The Dose Connection
The degree of heart rate reduction tracks directly with how much metoprolol is circulating in your blood. Higher plasma levels mean a slower heart rate. One study found that patients who developed symptomatic slow rhythms were taking a median daily dose of 200 mg, compared to 100 mg in those who didn’t have problems. The average daily dose across a large population-based study was around 90 mg.
There’s a ceiling to the drug’s intended effect. Plasma concentrations between 80 and 100 micrograms per liter produce maximal blockade of the beta-1 receptors. Above that range, the drug starts blocking beta-2 receptors as well (found in the lungs and blood vessels), which doesn’t slow the heart further but does increase the chance of other side effects.
Sex Differences in Response
Women appear more sensitive to metoprolol’s heart-rate-lowering effect than men. In a population-based study, higher drug levels in women were significantly associated with lower heart rates, while the same relationship did not hold in men. Women with the highest plasma levels had roughly 15 times the odds of bradycardia compared to women with the lowest levels. In men, the difference was not statistically meaningful. This may partly explain why some women experience noticeable slowing at doses that seem well tolerated in men.
Who Is Most at Risk
Older adults face a higher risk of developing a problematically slow heart rate on metoprolol. Aging changes the heart’s electrical system and reduces the body’s ability to compensate when a drug slows things down. The response to adrenaline naturally weakens with age, and reflexes that normally adjust heart rate become blunted. In one hospital-based study, older age was a significant predictor of symptomatic slow rhythms in patients taking beta-blockers, but not in patients who weren’t on them. Metoprolol was the most commonly identified beta-blocker among patients who developed these problems.
People with pre-existing electrical conduction issues in the heart are also at greater risk. Conditions like first-degree heart block, sick sinus syndrome, or other conduction delays can be worsened by the drug’s effect on signal transmission through the heart.
Drug Combinations That Increase Risk
Certain medications amplify metoprolol’s heart-slowing effect. The most important ones to know about are the calcium channel blockers verapamil and diltiazem. Both of these drugs independently slow the heart’s electrical conduction, so combining them with metoprolol creates an additive effect. Verapamil and diltiazem can also reduce the body’s ability to clear metoprolol from the bloodstream, effectively raising the drug’s levels beyond what the dose alone would suggest.
Other drugs that slow heart rate or affect cardiac conduction, including certain antiarrhythmic medications and some antidepressants, can also compound the problem. If you take metoprolol alongside any of these, your prescriber will typically monitor your heart rate more closely.
Symptoms to Watch For
A low heart rate on its own isn’t necessarily a problem. Many people on metoprolol see resting rates in the 50s and feel perfectly fine. The issue arises when the heart can’t pump enough blood to meet the body’s needs. When that happens, you’ll typically notice some combination of the following:
- Dizziness or lightheadedness, especially when standing up from a sitting or lying position
- Unusual fatigue or weakness that goes beyond normal tiredness
- Blurred vision or difficulty concentrating
- Chest discomfort or a feeling of tightness
- Fainting or near-fainting, which is the most concerning sign and warrants immediate medical attention
- Shortness of breath, particularly with minimal exertion
These symptoms tend to be worse during physical activity, when the heart would normally speed up to deliver more oxygen but can’t because the drug is holding it back. If your resting heart rate is consistently below 50 and you’re experiencing any of these symptoms, that’s a signal the current dose may be too high for you.
What You Can Do About It
If you suspect metoprolol is making your heart rate too low, the most useful thing you can do immediately is start tracking your resting heart rate. Check it first thing in the morning before getting out of bed, using a pulse oximeter, fitness tracker, or by counting your pulse for 60 seconds. A few days of consistent readings gives your doctor real data to work with.
Dose adjustments are the most common fix. Because the heart rate effect is directly tied to how much drug is in your system, lowering the dose usually brings the heart rate back up. Switching from the immediate-release to the extended-release formulation is another option, since it produces more stable drug levels throughout the day with fewer peaks that can trigger bradycardia. Abruptly stopping metoprolol is not safe, as it can cause a rebound spike in heart rate and blood pressure. Any changes need to be gradual and supervised.