The Propranolol dosage you're prescribed will depend on what you're being treated for.
In the case of Propranolol for anxiety, doctors most commonly prescribe 10-20 mg. This is meant to be taken one hour before an event.
This dosage is much lower than what's often prescribed to treat other conditions including chest pain or high blood pressure. In most cases, these other types of treatment, like heart conditions and high blood pressure, call for dosages of up to 80-300 mg.
To minimize your chances of experiencing side effects, it's important to take your medication as it's prescribed to you.
While in some cases, your doctor may recommend more than Propranolol 10 mg for certain treatments, it's important you do not change your dosage unless you speak to your healthcare provider first.