Metoprolol (brand names Lopressor, Toprol-XL) is a widely prescribed beta-blocker used to treat high blood pressure, angina (chest pain), heart failure, and to prevent migraines. It works by blocking the effects of adrenaline (epinephrine) on the heart and blood vessels, which slows the heart rate and lowers blood pressure.
While metoprolol is a lifesaving medication for millions of people, it does come with a distinct side effect profile. Because it affects the nervous system and blood flow, the side effects can sometimes feel strange or alarming if you aren’t expecting them.
Here are the 10 most important metoprolol side effects you should know about, ranked from most common to most serious.
1. Extreme Fatigue and Weakness
Because metoprolol literally slows down your heart rate and reduces the amount of oxygen-rich blood being pumped to your muscles, feeling tired is the number one complaint.
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What it feels like: Feeling winded walking up stairs, struggling to finish a workout, or feeling like your limbs are heavy.
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Note: This often improves after a few weeks as your body adjusts to the new, slower heart rate.
2. Dizziness and Lightheadedness
Metoprolol lowers your blood pressure. If your blood pressure drops too low—especially when you stand up quickly from a sitting or lying position (orthostatic hypotension)—your brain temporarily lacks blood flow.
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What it feels like: Feeling faint, seeing stars, or feeling unsteady on your feet.
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Tip: Stand up slowly, and stay well-hydrated.
3. Cold Hands and Feet
Because metoprolol narrows the blood vessels slightly and reduces the force of the blood pumping to your extremities, your fingers and toes may feel unusually cold or even numb.
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What it feels like: Persistent coldness in the hands/feet, even in warm rooms, or a tingling sensation.
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Tip: Wearing socks and gloves can help, but mention this to your doctor if it becomes painful or turns your fingers blue (Raynaud’s phenomenon).
4. Sleep Disturbances and Vivid Dreams
Unlike some other beta-blockers, metoprolol crosses the blood-brain barrier. It can interfere with melatonin production and the REM cycle of sleep.
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What it feels like: Insomnia, waking up multiple times a night, or experiencing intensely vivid, bizarre, or unpleasant nightmares.
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Tip: If this happens, ask your doctor if you can take your last dose earlier in the day, or switch to the extended-release version if you are on the immediate-release.
5. Bradycardia (Abnormally Slow Heart Rate)
This is the intended mechanism of the drug, but sometimes it works too well. A normal resting heart rate is 60–100 beats per minute. Metoprolol can push it below 50.
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What it feels like: If your heart rate drops too low, you may feel dizzy, short of breath, or like you might pass out.
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Red Flag: If you take your pulse and it is consistently below 50 BPM and you feel unwell, call your doctor immediately.
6. Weight Gain
Metoprolol can cause a modest weight gain (usually 2 to 5 pounds) in the first few months. This happens for two reasons: it slightly slows down your metabolism, and if it is causing fatigue, you may be less physically active. It can also cause mild fluid retention.
7. Stomach Upset, Nausea, or Diarrhea
When you start taking metoprolol, the changes in blood flow and nervous system signaling can irritate the gastrointestinal tract.
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What it feels like: Mild nausea, stomach cramps, heartburn, or loose stools.
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Tip: Taking metoprolol with food (especially the immediate-release version) can significantly reduce stomach upset.
8. Sexual Dysfunction and Erectile Dysfunction (ED)
Beta-blockers are notorious for causing sexual side effects. Because metoprolol reduces blood flow to the extremities and dulls the adrenaline response, men may find it difficult to achieve or maintain an erection, and both men and women may experience a reduced libido.
Important: Never stop taking the medication because of this; your doctor can often lower the dose or switch you to a different class of blood pressure medication that doesn’t have this side effect.
9. Shortness of Breath (Bronchospasm)
While cardioselective beta-blockers like metoprolol are safer than older beta-blockers, they can still affect the lungs at higher doses.
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What it feels like: Wheezing, chest tightness, or feeling like you can’t catch your breath.
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Red Flag: If you have a history of Asthma or COPD, you must be monitored closely on this drug. If you experience sudden shortness of breath, seek medical attention immediately.
10. Depression and Mood Changes
Because metoprolol affects the central nervous system and blocks adrenaline (the “fight or flight” hormone), some patients report feeling emotionally flat, lethargic, or clinically depressed.
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What it feels like: Lack of motivation, unexplained sadness, or a loss of interest in hobbies.
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Note: This is more common in elderly patients. If your mood has shifted significantly since starting the drug, tell your doctor—there are alternative medications available.
⚠️ The Golden Rule: Never Stop “Cold Turkey”
The most dangerous side effect of metoprolol doesn’t happen while you are taking it; it happens if you stop taking it suddenly.
Because your body has adapted to the drug, stopping it abruptly causes a massive surge of adrenaline. This can lead to rebound hypertension (dangerously high blood pressure), severe chest pain, or even a heart attack.
If you and your doctor decide metoprolol is not right for you, they will give you a schedule to “wean” off it slowly over one to two weeks.