Propranolol: what it treats, how to take it, side effects
Last updated September 3, 2026.
Propranolol is the original beta blocker - it relaxes blood vessels and slows the heart rate. You may know it as Inderal. Its indication list is one of the longest in medicine, covering the heart, the head, and the shakes.
What does it treat?
High blood pressure, irregular heartbeats, angina (chest pain), certain types of tremor, a heart muscle disease called hypertrophic subaortic stenosis, the adrenal tumor pheochromocytoma, and migraine prevention - plus improving survival after a heart attack.
How do you take it?
The regular tablet and liquid are taken 2 to 4 times a day; the extended-release capsule once a day, sometimes at bedtime, with or without food as directed - same times every day. Swallow extended-release capsules whole, never split, chew, or crush. Measure the liquid with an oral syringe or dosing cup, not a kitchen spoon. Your doctor starts low and increases gradually while your body adjusts. It controls your condition but does not cure it. Never stop suddenly: MedlinePlus warns that suddenly stopping can cause serious heart problems - your doctor tapers. Missed dose: take it when you remember unless the next one is close; never double up.
Side effects to know
- Common: dizziness or lightheadedness, tiredness, diarrhea, and constipation.
- Serious: allergic reactions (rash, itching, hives, blistering or peeling skin, trouble breathing or swallowing, facial or throat swelling); feeling faint; unusual weight gain; shortness of breath; and irregular heartbeat. Call your doctor immediately or get emergency care.
Who should not take it?
Anyone with asthma or other lung disease, a slow or irregular heartbeat, or heart failure - MedlinePlus says your doctor may rule it out in all three, because a nonselective beta blocker can tighten airways and slow the heart further. Flag heart, liver, or kidney disease, diabetes (it can mask low-blood-sugar warning signs), pheochromocytoma, and an overactive thyroid. Tell the surgeon or dentist before any procedure. Alcohol can increase the amount of propranolol in your body - ask your doctor about it. Pregnancy and breastfeeding need a direct call.
When is it an emergency?
Call 911 for fainting, severe shortness of breath, or trouble breathing or swallowing. For an overdose (slow heartbeat, dizziness, weakness, fainting, difficulty breathing), 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 people with asthma take propranolol?
Because it blocks beta receptors everywhere, including the lungs. MedlinePlus says to tell your doctor if you have asthma or other lung disease - your doctor may tell you not to take propranolol, since it can tighten airways and trigger breathing problems. Newer beta blockers that target the heart more selectively are the usual alternative.
Why can't I stop propranolol suddenly?
MedlinePlus says it plainly: if you suddenly stop taking propranolol, you may experience serious heart problems. Beta blockers change how the heart responds to stress hormones, and stopping cold removes the shield all at once - blood pressure and heart rate can spike. Your doctor tapers the dose gradually.
Can I drink alcohol while taking propranolol?
Ask your doctor first. MedlinePlus says alcohol may increase the amount of propranolol in your body, which pushes blood pressure and heart rate lower than intended. That is a dose-and-timing conversation for whoever prescribed it.
Does propranolol hide low blood sugar?
It can mask the warning signs. MedlinePlus flags diabetes on the tell-your-doctor list because propranolol blunts the pounding heart and shaking that normally tell a person with diabetes their sugar is crashing. If you use insulin or diabetes medications, your monitoring plan needs to account for that.
Why is propranolol used for stage fright and tremor?
It blocks the physical symptoms of adrenaline - shaking hands, racing heart, quavering voice. For essential tremor it is a standing daily treatment; for performance anxiety, some doctors prescribe a single dose before an event. Same drug, different schedules - your doctor decides which pattern fits.
What happens if I miss a dose of propranolol?
Take it as soon as you remember, unless it is almost time for the next one - then skip it and never double up. With a 2-to-4-times-daily schedule, an anchor habit (meals and bedtime) keeps the rhythm.