Propranolol is a commonly prescribed beta blocker medication. Developed in the 1960s, propranolol is approved by the FDA to treat high blood pressure, angina and certain other conditions. However, like other beta blockers — and pretty much every medication out there — potential side effects are things you should definitely be aware of and consider before taking it.
Most side effects of propranolol are minor and temporary. However, this medication also has the potential to cause more serious side effects that you should be aware of. We’ve listed all of these side effects below, as well as information on how and why each side effect has the potential to occur. Make sure to discuss potential side effects with your doctor and contact your doctor immediately if you experience any side effects.
Common Side Effects of Propranolol
Although serious side effects from propranolol are rare, it’s quite common to experience some of the more minor ones. We’ve listed all of these side effects below, as well as what to expect if you experience them after using propranolol.
Lower-than-Normal Heart Rate
It’s normal to have a slightly lower heart rate after taking propranolol. Propranolol works by blocking the effects of adrenaline on your heart, meaning you’ll maintain a slightly lower heart rate than you would in normal conditions.
This is usually not dangerous unless your heart rate drops below 50 beats per minute. We’ve explained this in more detail below, under the “Bradycardia” heading.
Fatigue is one of the most common side effects of propranolol. Data from the National Library of Medicine lists fatigue as a common adverse central nervous system effect of propranolol, noting that fatigue and lethargy become more common at dosages exceeding 160 mg per day.
Like many other side effects of propranolol, fatigue can often be reduced or avoided by lowering your dosage of the medication. Fatigue is most common after you first begin to take propranolol and often goes away over the course of several weeks or months.
Propranolol, as well as other beta blockers, has been shown in some studies to reduce your body’s secretion of melatonin — an important hormone for optimal sleep. For a small percentage of propranolol users, this can lead to difficulties falling — and staying — asleep.
Propranolol is also linked to other sleep-related issues, including nightmares and drowsiness. Like fatigue, sleep issues from propranolol are most common shortly after you start to use the medication.
Like other propranolol side effects, insomnia might be preventable by reducing your dose of the medication. A 2012 study showed that using melatonin supplements can also help to improve sleep quality if you use a beta blocker to treat hypertension.
Diarrhea is a potential side effect of many beta blockers, including propranolol. As with many other side effects, diarrhea from propranolol can reverse after you stop using the medication, or after adjusting your dosage.
Propranolol and several other beta blockers (metoprolol and timolol) are linked to some level of hair loss. Unlike permanent hair loss from male pattern baldness, which can be caused by sensitivity to DHT, the temporary hair loss from propranolol is caused by telogen effluvium.
This means that any hair you lose from propranolol isn’t permanently gone. Instead, it’s a result of some hairs prematurely exiting the growth phase of the hair cycle.
Overall, hair loss from propranolol seems to be uncommon.
Propranolol and other beta blockers can interfere with your body’s production of certain proteins, including the proteins used to produce tears. Beta blockers can also reduce the pressure in your eyes, resulting in lower amounts of moisture and excessive dryness.
If you get dry eyes after using propranolol, make sure you discuss it with your doctor during your next appointment. Dry eyes can usually be treated using eye drops or avoided by using a lower dose of propranolol.
Serious Propranolol Side Effects
Overall, propranolol is generally unlikely to cause serious side effects. However, it is possible for them to occur. If you experience any of the side effects listed below, contact your doctor as soon as possible for assistance.
Bradycardia (Reduced Heart Rate)
Propranolol is a type of beta blocker, meaning it blocks the action of stress hormones such as adrenaline on the beta receptors of the heart.
This means you might experience a slightly low heart rate while using propranolol. If you take too large a dose of propranolol, it can lead to a condition known as bradycardia, in which your heart rate drops below 60 beats per minute.
If your heart rate is lower than 50 beats per minute (while awake) after using propranolol and you are not a trained athlete, you should contact your doctor immediately. A heart rate below this level can lead to fatigue or fainting and typically requires treatment.
Bradycardia from propranolol is usually treated by adjusting your dosage of the medication or preventing interactions with other drugs that can affect your heart rate. The propensity for propranolol interactions is generally low, but it’s important to be mindful.
Hypoglycemia (Low Blood Sugar)
Nonselective beta blockers such as propranolol can inhibit glycogenolysis, the process by which your body breaks down glycogen to glucose. This can lead to hypoglycemia, or low blood sugar.
Because propranolol blocks the effects of adrenaline on the heart and other tissue that contains beta receptors, it can also mask the physical effects of hypoglycemia.
Because of this, people with diabetes should use extra caution when using nonselective beta blockers such as propranolol and should only take propranolol under a doctor’s care.
Cold Hands and/or Feet
Propranolol and other beta blockers can reduce blood pressure to your extremities, resulting in cold, numb hands and/or feet. This is a fairly well-known but rare side effect of propranolol that’s called drug-related Raynaud’s phenomenon.
While a mild drop in the temperature of your hands and feet is usually nothing to feel concerned about, it’s important to contact your doctor if your hands and/or feet feel numb, painful or overly cold after using propranolol.
Rapid Weight Gain/Fluid Retention
Propranolol can cause your body to retain more fluid than normal, leading to a sudden increase in your bodyweight. This is not usually due to fat gain — instead, your body will simply hold more liquid than normal.
Use of beta blockers (especially older ones like atenolol [Tenormin] and metoprolol [Lopressor, Toprol-XL]) may result in an average weight gain of about 2.6 lbs, although some patients may gain more. If you experience significant weight gain after starting propranolol, it’s important to contact your doctor.
Severe Nausea, Diarrhea and/or Vomiting
Although rare, propranolol can potentially cause severe nausea, vomiting and diarrhea in some people.
These symptoms are often associated with an overly high dose of propranolol.
As with other serious side effects of propranolol, if you experience severe nausea, vomiting or diarrhea, you should contact your doctor as soon as possible.
Shortness of Breath
Propranolol is a nonselective beta blocker, meaning it affects beta receptors both in the heart and in other organs.
Stress hormones like adrenaline play a role in helping you breathe smoothly and easily. When you use propranolol, it can block the effects of adrenaline on your lungs, potentially making you feel short of breath.
Like other side effects of propranolol, shortness of breath is uncommon. However, it can affect you if you have asthma, chronic lung disease or other health conditions that make it difficult to breathe, especially after physical exertion.
Selective beta blockers, which are designed specifically to block the effects of stress hormones on the heart, do not normally cause shortness of breath and may be a safer alternative to propranolol if you have asthma or other breathing conditions.
Although propranolol is not known to have significant effects on vision, a small percentage of propranolol users have reported hallucinations after taking the medication.
In clinical studies, between 0.3 percent and 0.6 percent of people treated using propranolol reported seeing visual hallucinations. In some studies, including the one linked above, up to 17.5 percent of participants reported some level of visual activity after taking propranolol.
If you experience hallucinations after using propranolol, you should contact your doctor as soon as possible. In studies, visual hallucinations from beta blockers typically disappear quickly after people stop using the medication or switch to an alternative beta blocker.
Learn More About Propranolol
Our Propranolol 101 guide goes into more detail on how propranolol works as a medication, from its effects to its dosage forms. You can also learn more about using propranolol in our guide to propranolol for performance and social anxiety.