Many people taking the medication propranolol experience headache as a primary side effect. Propranolol is a beta-blocker drug typically prescribed as a blood pressure medication, but it can also be used to treat a variety of other conditions, such as hypertension, arrhythmia, angina, and more. Clinical studies have shown that headaches are a common adverse effect of propranolol. It has been reported in up to 25% of people taking the medication. Headaches due to propranolol can range from mild to severe, and may be worse when the drug is taken with other drugs that can cause headaches, such as alcohol. The mechanism of how propranolol leads to headache is not well understood. Some researchers suggest that beta blockade, the primary action of propranolol, can interfere with brain functions such as neurotransmitter release, leading to decreased blood flow to the brain and resulting in headache. If you experience headaches while taking propranolol, it is important to talk to your doctor. Your doctor may adjust the dosage or switch you to another medication with fewer side effects. Non-drug treatments, such as relaxation techniques or acupuncture, may also be helpful in relieving headaches caused by propranolol.