Metoprolol: what it treats, how to take it, side effects
Last updated September 3, 2026.
Metoprolol is a beta blocker that slows your heart rate and relaxes blood vessels so the heart works less hard. You may know it as Lopressor (the regular tablet) or Toprol-XL (the extended-release version). It controls heart conditions rather than curing them - and stopping it suddenly can cause serious heart problems.
What does it treat?
High blood pressure, angina (chest pain), and heart failure, plus improving survival after a heart attack. MedlinePlus adds certain irregular heartbeats as another use. It works by relaxing blood vessels and slowing heart rate to improve blood flow and decrease blood pressure.
How do you take it?
The regular tablet (tartrate) goes down once or twice a day with meals or immediately after - the label starts most adults at 100 mg daily in single or divided doses, adjusted weekly. The extended-release tablet or capsule is once a day, same time. The ER tablet may be split in half but never chewed or crushed; the ER capsule can be opened and sprinkled on a spoonful of applesauce, pudding, or yogurt, swallowed immediately. The rule that matters most: do not stop taking metoprolol without talking to your doctor. Stopping suddenly can trigger serious heart problems - the label tapers off over 1 to 2 weeks when it is time to stop. Missed dose: MedlinePlus says skip it and return to schedule; never double up.
Side effects to know
- Common: dizziness or lightheadedness, tiredness, diarrhea, dry mouth, and rash or itching.
- Serious: shortness of breath or difficulty breathing, swelling of the hands, feet, ankles, or lower legs, weight gain, fainting, and a rapid, pounding, or irregular heartbeat - call your doctor immediately or get emergency care.
Who should not take it?
If you have a slow or irregular heartbeat or certain heart failure, your doctor may rule metoprolol out. Flag asthma or other lung disease, circulation problems, pheochromocytoma, heart or liver disease, diabetes, and an overactive thyroid. Three specific warnings from MedlinePlus: it can hide the warning signs of low blood sugar, so people with diabetes need to know what to watch for; allergic reactions may be worse on it and may not respond to usual epinephrine doses; and if you take the extended-release capsules, do not drink any alcohol or take medications containing alcohol - it changes how the drug releases. Mention it before any surgery, including dental work. Pregnant, planning pregnancy, or breastfeeding: tell your doctor first.
When is it an emergency?
Difficulty breathing, fainting, or a pounding irregular heartbeat means calling your doctor immediately or getting emergency care. Swelling with weight gain can signal fluid retention - same-day call. For an overdose, call Poison Control at 1-800-222-1222. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper.
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Common questions
Why can't I stop metoprolol suddenly?
Because the heart adapts to it. MedlinePlus warns that suddenly stopping metoprolol can cause serious heart problems, and the label says to reduce the dose gradually over 1 to 2 weeks when discontinuing. If side effects are bothering you, the answer is a taper plan with your doctor, not a hard stop.
What is the difference between metoprolol tartrate and succinate?
Release timing. The tartrate (Lopressor-style) tablet is taken once or twice a day with meals or right after, per the label. The succinate extended-release forms are once a day - the ER tablet can be split but not chewed or crushed, and the ER capsule can be opened and sprinkled on soft food. Same medicine, different clocks; do not swap one for the other without your doctor.
Can I drink alcohol while taking metoprolol?
With the extended-release capsules, no. MedlinePlus says do not drink any alcoholic drinks or take medications containing alcohol if you are taking metoprolol extended-release capsules, because alcohol changes how the drug releases. For other forms, alcohol can deepen the dizziness - ask your doctor what applies to your prescription.
Does metoprolol affect blood sugar?
It can mask the alarms. MedlinePlus says metoprolol may increase the risk of hypoglycemia and prevent the warning signs that would tell you your blood sugar is low. If you have diabetes, learn the subtler signals and let your doctor know if you are unable to eat or drink normally or are vomiting while on it.
Will metoprolol make me tired?
Often, at first. Tiredness and dizziness or lightheadedness top MedlinePlus's common side effect list, and both usually ease as your body adjusts over days to weeks. Fatigue that persists or worsens - especially with shortness of breath, swelling, or weight gain - is a call-your-doctor pattern.
I have asthma - can I take metoprolol?
That needs your doctor's explicit decision. MedlinePlus lists asthma and other lung diseases among the conditions to disclose before taking it, because beta blockers can tighten airways. It also notes allergic reactions may be worse on metoprolol and may not respond to usual epinephrine doses - both facts belong in front of your prescriber.